The Racket Mode package consists of a variety of Emacs major and minor modes, including:
racket-mode
: A major mode to edit .rkt
files. Generally assumes #lang racket
.
racket-mode
using behavior specified by a #lang
for colors, indent, expression navigation, etc. Experimental.
racket-repl-mode
: A major mode to run programs and use a REPL.
For code, issues, and pull requests, see the Git repo.
To sponsor this work, see GitHub Sponsors or PayPal.
The most common way to use Racket Mode is to install from a package archive like MELPA or NonGNU ELPA.
Some people also use a system like straight.el.
Note that Racket Mode is only available on MELPA (not “MELPA Stable”), and is available as a “rolling release” from NonGNU ELPA.
Emacs 28.1 or newer comes configured to use NonGNU ELPA, in which case you can skip ahead to Install.
With older versions of Emacs, you can use MELPA.
Following is a quick guide that may work for you. (For definitive instructions and the latest trouble-shooting tips, please see https://melpa.org/#/getting-started.)
(require 'package) (add-to-list 'package-archives '("melpa" . "https://melpa.org/packages/") t) (package-initialize)
NOTE: If you ever get an error message about “contacting a host” or “downloading an archive”, the problem is not unique to Racket Mode. Please see https://melpa.org/#/getting-started.
When Emacs is configured to use NonGNU ELPA or MELPA:
package-initialize
RET .
package-refresh-contents
RET .
package-install
RET racket-mode
RET .
NOTE: If you get an error message about “contacting a host” or “downloading an archive”, the problem is not unique to Racket Mode. Please see https://melpa.org/#/getting-started.
If you have installed the minimal Racket distribution (for example by using the homebrew formula) Racket Mode needs some additional Racket packages. A simple way to get all these packages is to install the drracket
Racket package. In a command shell:
raco pkg install --auto drracket
A more-targeted approach is instead to install these specific packages and their dependencies:
raco pkg install --auto data-lib errortrace-lib macro-debugger-text-lib rackunit-lib racket-index scribble-lib drracket-tool-text-lib
If you do not want to use racket-xp-mode
, then you can omit drracket-tool-text-lib
.
On a headless server, you might want to omit gui-lib
. Unfortunately, racket-doc
depends on gui-lib
. On the one hand, if you uninstall racket-doc
and gui-lib
, you will no longer be able to access documentation when using a Racket Mode back end running there. On the other hand, if you leave gui-lib
installed, you should be careful to run the Racket Mode back end using xvfb-run racket
.
To uninstall Racket Mode, simply type M-x package-delete
RET racket-mode
RET .
You should probably also exit and restart Emacs.
The “easy path” provided by Emacs is to update all packages to their latest versions. Although you might not want to do this — see next section — here is how to do so:
package-initialize
.
package-refresh-contents
.
list-packages
. It should display a message like “42 packages can be upgraded; type ‘U’ to mark them for upgrading.”.
After such a mass update, it might be wise to exit and restart Emacs.
NOTE: If you get an error message about “contacting a host” or “downloading an archive”, the problem is not unique to Racket Mode. Please see https://melpa.org/#/getting-started.
Updating all packages sometimes is more than you want. For example, maybe you will discover that some packages have changed in ways that require you to take time to learn about, change customizations, and so on.
To update just Racket Mode:
Although Racket Mode can be customized with many Variables, there is only one that you might need to set: racket-program. This is the name or pathname of the Racket executable. It defaults to Racket.exe
on Windows else racket
.
On Windows or Linux, this default will probably work for you.
On macOS, downloading Racket doesn’t add its bin
directory to your PATH
. Even after you add it, GUI Emacs doesn’t automatically use your path (unless you use the handy exec-path-from-shell package). Therefore you might want to set racket-program
to a complete pathname.
You can setq
this directly in your Emacs init file (‘~/.emacs’ or ‘~/.emacs.d/init.el’), or, use M-x customize
, as you prefer.
Racket is a programming language.
Racket is also a “language-oriented programming language”. Most Racket source files contain a ‘#lang‘ line. The lang may be an s-expression lang like racket
, or an at-expression lang like scribble/manual
, or something completely different like datalog
or rhombus
.
The Racket Mode package offers a choice of two major modes to use in buffers for viewing and editing source code. Each has pros and cons.
Whereas racket-mode
is in the tradition of Emacs lisp-mode
and scheme-mode
and assumes s-expression langs, racket-hash-lang-mode
takes the approach of DrRacket to work for all langs.
racket-mode
is the original, “classic” mode for #lang racket
and related s-expression languages. It is implemented entirely in Emacs and does not need Racket Mode’s back end racket process running. Font-lock (coloring) uses rules for a fixed set of identifiers from racket
lang and popular modules like racket/match
. Indentation uses rules for a fixed set of forms, and may be customized.
racket-hash-lang-mode
uses font-lock (colors) and indentation determined by the lang; to get this information it does need the Racket Mode’s back end racket process running. Although basic editing should feel fast, you might notice some delay when indenting. You might see colors appear after a small delay (but it will not block editing). Speaking of colors, they will be “plainer” than racket-mode
– just colors for tokens like numbers, comments, strings, and keywords. This looks similar to DrRacket. However you can enhance this in various ways; see the discussion of racket-hash-lang-module-language-hook.
You can use different major modes for different kinds of files:
.rkt
files and s-expression langs, which mode to use is personal preference.
.scrbl
and at-expression langs like scribble/manual
, racket-hash-lang-mode
is probably better than racket-mode
. (Note there is also an unrelated scribble-mode
package.)
datalog
or rhombus
(.rhm
), racket-hash-lang-mode
is definitely better than racket-mode
. (Note there is also an unrelated rhombus-mode
package.)
You can use auto-mode-alist
to tell Emacs which major mode to use initially for certain file extensions. Also, in a buffer you can use M-x racket-mode
and M-x racket-hash-lang-mode
to switch between them.
To customize things like key bindings, you can use racket-mode-hook
in your Emacs init file to modify racket-mode-map
. For example, although C-c C-c is bound by default to the racket-run
command, let’s say you wanted F5 to be an additional binding:
(add-hook 'racket-mode-hook (lambda () (define-key racket-mode-map (kbd "<f5>") 'racket-run)))
Likewise for racket-repl-mode-hook
and racket-repl-mode-map
.
Note: The alternative major mode racket-hash-lang-mode disables all of the following behavior and uses colors determined by the #lang.
Font-lock (as Emacs calls syntax highlighting) can be controlled using the variable font-lock-maximum-decoration
, which defaults to t
(maximum). You can set it to a number, where 0
is the lowest level. You can even supply an association list to specify different values for different major modes.
Historically you might choose a lower level for speed. These days you might do so because you prefer a simpler appearance.
Racket Mode supports four, increasing levels of font-lock:
0
: Just strings, comments, and #lang
.
1
: #:keyword
and self-evaluating literals like numbers, quoted symbols (including symbols with spaces delimited by |
characters), and #rx
and #px
regular expressions.
2
: Identifiers in define
-like and let
-like forms.
3
: Identifiers provided by racket
, typed/racket
, racket/syntax
, and syntax/parse
. (This level effectively treats Racket as a language, instead of a language for making languages.).
In Emacs, a major mode may supply a “completion-at-point function”. This function is used by manual completion commands like complete-symbol
(bound by default to C-M-i ), as well as by auto-completion packages like company-mode
.
racket-mode
supplies racket-complete-at-point
, which simply supplies the same symbols that it knows how to font-lock. This does not require the Racket Mode back end to be running. But of course the completion candidates do not correspond to your program’s definitions or those it imports. This is a static, “better than nothing” fallback.
racket-xp-mode
— an optional minor mode that enhances racket-mode
— supplies racket-xp-complete-at-point
, which uses a static analysis to find local and imported binding names. Although this requires the Racket Mode back end to be running — and will automatically start it — it does not require the edit buffer to be racket-run
. This also supplies meta data usable by the company-capf
backend.
racket-repl-mode
supplies racket-repl-complete-at-point
, which uses the result of namespace-mapped-symbols
on the program currently running in the REPL.
These completion functions are set by default. (However, racket-xp-mode
is not enabled by default. To do so: racket-xp-mode.)
If you want TAB to do completion as well as indent, add the following to your Emacs init file:
(setq tab-always-indent 'complete)
This changes the behavior of Emacs’ standard indent-for-tab-command
, to which TAB is bound by default in racket-mode
and racket-repl-mode
.
Sometimes Racket Mode asks for input in the minibuffer. To do so it uses the standard Emacs function completing-read
, so as to be compatible with all Emacs packages that enhance completing-read
, such as helm, ivy, ido-completing-read+, vertico, and so on.
(Earlier versions of Racket Mode sometimes used ido-completing-read
. If you have upgraded Racket Mode and miss that, simply install the ido-completing-read+ package.)
Several modes support the Emacs commands
xref-find-definitions
xref-find-references
xref-pop-marker-stack
To do so, each mode adds a local hook for xref-backend-functions
:
#'racket-mode-xref-backend-function
#'racket-xp-xref-backend-function
#'racket-repl-xref-backend-function
If you prefer, you can remove the local hook — e.g. for racket-mode
: (remove-hook 'xref-backend-functions #'racket-mode-xref-function t)
.
You can M-x customize-group
and enter xref
to adjust some other settings. For example, the customization variable xref-prompt-for-identifier
controls which commands prompt you and when. You might prefer to set it to nil
.
If you use paredit
, by default it binds M-? to paredit-convolute-sexp
. You can change that binding in paredit-mode-map
allowing the global binding for M-? to be used, or, pick some other key for xref-find-references
in the global map.
Finally, what to expect:
racket/base
, typed/racket/base
, and other modules.
As a result, to find a definition, it is necessary to know exactly which identifier is meant — either by expanding the module (as is done by racket-xp-mode
) or by actually running it (racket-repl-mode
). Once known, we can usually find the definition site, even through a chain of renaming and/or contract-wrapping exports. In addition, when point is on a module within require
form, we can usually find the source file. (In plain racket-mode
edit buffers not enhanced by racket-xp-mode
, the only thing that xref-find-definitions
does is visit relative requires, e.g. foo.rkt
in (require "foo.rkt")
.)
As for finding references, the default xref implementation is used, which greps for strings among a project’s files. Although racket-xp-mode
can sometimes do better, using drracket/check-syntax
for definitions and references within the current buffer, beyond those it also falls back to the default implementation.
In any case, using the Emacs xref API allows for consistent command names, shortcut keys, and even a special buffer to navigate among references and visit each source location.
Note: The alternative major mode racket-hash-lang-mode disables all of the following behavior and uses indentation determined by the #lang.
Indentation can be customized in a way similar to lisp-mode and scheme-mode: racket-indent-line.
(Indentation preserves your line breaks. If you want to use an auto-reformatter — an expressive pretty printer that chooses line breaks while computing an optimal layout — the Racket package fmt is supported by the Emacs package emacs-format-all-the-code.)
Note: If you use racket-hash-lang-mode, see racket-hash-lang-module-language-hook for how to enable/disable paredit based on the specific #lang.
If you use paredit, you might want to add keybindings to paredit-mode-map
:
paredit-open-curly
and paredit-close-curly
.
paredit-wrap-square
and paredit-wrap-curly
.
For example, with use-package
:
(use-package paredit :ensure t :config (dolist (m '(emacs-lisp-mode-hook racket-mode-hook racket-repl-mode-hook)) (add-hook m #'paredit-mode)) (bind-keys :map paredit-mode-map ("{" . paredit-open-curly) ("}" . paredit-close-curly)) (unless terminal-frame (bind-keys :map paredit-mode-map ("M-[" . paredit-wrap-square) ("M-{" . paredit-wrap-curly))))
Starting c. November 2022, paredit binds the RET key to its own command. Unfortunately this is not compatible with interactive modes — including but not limited to racket-repl-mode
— which expect RET to be bound to a command to submit your input to the REPL. In other words, if you type an expression and hit RET , nothing will happen and the REPL will seem frozen. You M-x racket-repl-submit
to proceed.
If you want to use paredit with interactive modes, their advice is to remove the binding from paredit-mode-map
(note that this will also disable it for all buffers, including editing buffers). One way you can do this for all related keys:
(dolist (k '("RET" "C-m" "C-j")) (define-key paredit-mode-map (kbd k) nil))
Note: If you use racket-hash-lang-mode, see racket-hash-lang-module-language-hook for how to enable/disable smartparens based on the specific #lang.
If instead of paredit you prefer smartparens, you can use the default configuration it provides for Lisp modes generally and for Racket Mode specifically:
(require 'smartparens-config)
If you prefer parentheses to appear “dimmed”, see paren-face.
If you prefer the opposite, see rainbow-delimiters.
By default, all racket-mode
edit buffers share one racket-repl-mode
buffer, named *Racket REPL*
. For example, if you run foo.rkt, the REPL prompt changes to foo.rkt>
, and the REPL is inside the file module namespace. If you then run bar.rkt, the REPL prompt changes to bar.rkt>
, and you are in that namespace.
If you prefer, you can use more than one REPL buffer, by customizing the variable racket-repl-buffer-name-function:
*Racket REPL <project-name>*
.
*Racket REPL <file.rkt>*
.
You can customize where the REPL buffer is displayed by adding an item to the Emacs variable display-buffer-alist
. A good regular expression to use for this would be \\`\\*Racket REPL
. For example, if you wanted to make the REPL buffer appear in a new frame:
(add-to-list 'display-buffer-alist '("\\`\\*Racket REPL" (display-buffer-reuse-window display-buffer-pop-up-frame) (reusable-frames . 0) (inhibit-same-window . t)))
Various modes add local hooks to eldoc-documentation-functions
.
racket-xp-mode
adds hooks to document the identifiers at point or at an apparent s-expression application head position. The identifiers are documented from check-syntax annotations. You may customize the variable racket-xp-eldoc-level to choose how much information is shown.
racket-repl-mode
adds hooks to describe the namespace identifers at point or at an apparent s-expression application head position. The description is a signature from surface syntax, or a Typed Racket type, or a “bluebox” for the namespace identifier.
Tip: With an eldoc-documentation-strategy
of eldoc-documentation-default
, these hooks show info about point when available, or else for the s-expression application head. You may change that to eldoc-documentation-compose
to show info for both positions when available.
Tip: Some people use the third-party package eldoc-box
to show information in a child frame (near point, or in a corner of the main frame) instead of the echo area.
Note: Racket Mode does not support the “old” eldoc API that uses eldoc-documentation-function
, singular.
An optional Emacs input method, racket-unicode
, lets you easily type various Unicode symbols that might be useful when writing Racket code.
To automatically enable the racket-unicode
input method in racket-mode
and racket-repl-mode
buffers, put the following code in your Emacs init file:
(add-hook 'racket-mode-hook #'racket-unicode-input-method-enable) (add-hook 'racket-repl-mode-hook #'racket-unicode-input-method-enable)
See racket-unicode-input-method-enable.
See racket-insert-lambda.
Prior to Emacs 28.0.50, things like auto-composition-mode
or ligature-mode
that use composition-function-table
to display ligatures can cause Emacs to freeze. This can happen when an Emacs overlay displays a string containing such a ligature. Although the problem is not limited to Racket Mode, it affects the overlays created by racket-show-pseudo-tooltip
, as used by racket-xp-mode
. The only known work-around is to change the value of racket-show-functions
to something “boring” such as (racket-show-echo-area)
.
Racket Mode consists of a single Emacs front end, and one or more processes running a back end written in Racket.1
A back end is responsible for commands that cannot be implemented in Emacs Lisp, as well as supplying zero or more REPLs.
Although you can start and stop a back end with racket-start-back-end
and racket-stop-back-end
, a back end is normally started automatically when the front end needs to issue some command. This includes commands that do not involve racket-run
or a REPL. For example racket-xp-mode
issues commands to check your code and annotate the buffer, even if you do not run it. In other words, a back end supplies zero or more REPLs — a back end is not the same thing as a REPL.
To learn more about how many REPLs are used: See racket-repl-buffer-name-function.
In the common case there is only one back end, on the same local host as Emacs, and it is used for .rkt
files in any directory.
However you can configure using any number of back ends on any number of local or remote host paths.
As one example, you can have multiple back ends on the local host. One back end is used for a project under a specific subdirectory, and the other back end for all others. (Perhaps one project needs Racket built from source, and everything else uses an installed, older version of Racket. By using different back ends, not only will racket-run
use the desired version of Racket for a file, so will commands for documentation or visiting definitions.)
(Note: If you use various versions of Racket via direnv
combined with the envrc
Emacs package, you still need a distinct back end for each project. To arrange this, add or modify a .dir-locals.el
file next to each .envrc
file; See racket-add-back-end.)
Furthermore, you could work with a project located on a remote host, whose files you edit using TRAMP. You also want the back end to run there. For a remote host, Racket Mode copies its back end source files to the remote when necessary, and runs the back end using ssh.
Of course the remote can also use different back ends for different paths.
And of course you can have multiple remotes.
If you need any of these “fancy” configurations: See racket-add-back-end.
However by default a configuration is automatically created for one back end on the local host. For that very common case, you don’t need to configure anything.
The following sections are generated from the doc strings for each command, variable, or face. (As a result, some of the formatting might not be quite as nice or correct as in the previous sections.)
You can also view these by using the normal Emacs help mechanism:
M-x racket-mode
Major mode for editing Racket source files.
Key | Binding |
} | racket-insert-closing |
] | racket-insert-closing |
) | racket-insert-closing |
TAB | indent-for-tab-command |
C-x C-e | racket-send-last-sexp |
C-M-y | racket-insert-lambda |
C-M-u | racket-backward-up-list |
C-M-x | racket-send-definition |
C-c C-u | racket-unfold-all-tests |
C-c C-f | racket-fold-all-tests |
C-c C-. | racket-describe-search |
C-c C-s | racket-describe-search |
C-c C-d | racket-documentation-search |
C-c C-p | racket-cycle-paren-shapes |
C-c C-x C-f | racket-open-require-path |
C-c C-e r | racket-expand-region |
C-c C-e e | racket-expand-last-sexp |
C-c C-e x | racket-expand-definition |
C-c C-e f | racket-expand-file |
C-c C-r | racket-send-region |
C-c C-o | racket-profile |
C-c C-l | racket-logger |
C-c C-t | racket-test |
C-c C-z | racket-edit-switch-to-repl |
C-c C-k | racket-run-module-at-point |
C-c C-c | racket-run-module-at-point |
In addition to any hooks its parent mode prog-mode
might have run,
this mode runs the hook racket-mode-hook
, as the final or
penultimate step during initialization.
C-M-y
Insert λ.
To insert Unicode symbols generally, see racket-unicode-input-method-enable.
M-x racket-tidy-requires
Make a single “require” form, modules sorted, one per line.
The scope of this command is the innermost module around point, including the outermost module for a file using a “#lang” line. All require forms within that module are combined into a single form. Within that form:
At most one required module is listed per line.
See also: racket-trim-requires and racket-base-requires.
M-x racket-trim-requires
Like racket-tidy-requires but also deletes unnecessary requires.
Note: This only works when the source file can be fully expanded with no errors.
Note: This only works for requires at the top level of a source file using #lang. It does NOT work for require forms inside module forms. Furthermore, it is not smart about module+ or module* forms – it might delete top level requires that are actually needed by such submodules.
See also: racket-base-requires.
M-x racket-base-requires
Change from “#lang racket” to “#lang racket/base”.
Adds explicit requires for imports that are provided by “racket” but not by “racket/base”.
This is a recommended optimization for Racket applications. Avoiding loading all of “racket” can reduce load time and memory footprint.
Also, as does racket-trim-requires, this removes unneeded modules and tidies everything into a single, sorted require form.
Note: This only works when the source file can be fully expanded with no errors.
Note: This only works for requires at the top level of a source file using #lang. It does NOT work for require forms inside module forms. Furthermore, it is not smart about module+ or module* forms – it might delete top level requires that are actually needed by such submodules.
Note: Currently this only helps change “#lang racket” to “#lang racket/base”. It does not help with other similar conversions, such as changing “#lang typed/racket” to “#lang typed/racket/base”.
M-x racket-add-require-for-identifier
Add a require for the identifier at point.
When more than one module supplies an identifer with the same name, they are listed for you to choose one. The list is sorted alphabetically, except modules starting with “racket/” and “typed/racket/” are sorted before others.
A “require” form is inserted into the buffer, followed by doing a racket-tidy-requires.
Caveat: This works in terms of identifiers that are documented. The mechanism is similar to that used for Racket’s “Search Manuals” feature. Today there exists no system-wide database of identifiers that are exported but not documented.
M-x racket-indent-line
Indent current line as Racket code.
Normally you don’t invoke this command directly. Instead, because
it is used as the value for the variable indent-line-function
in racket-mode and racket-repl-mode buffers, it is used
automatically when you press keys like RET or TAB. However you
might refer to it when configuring custom indentation, explained
below.
Following the tradition of lisp-mode
and scheme-mode
, the
primary way to determine the indentation of a form is to look for
a rule stored as a racket-indent-function
property.
To extend, use your Emacs init file to
(put SYMBOL 'racket-indent-function INDENT)
SYMBOL is the name of the Racket form like “test-case” and INDENT is an integer or the symbol “defun”. When INDENT is an integer, the meaning is the same as for lisp-indent-function and scheme-indent-function: Indent the first INDENT arguments specially and indent any further arguments like a body. (The number may be negative; see discussion below.)
For example:
(put 'test-case 'racket-indent-function 1)
This will change the indent of test-case
from this:
(test-case foo blah blah)
to this:
(test-case foo blah blah)
For backward compatibility, if racket-indent-function
has no
property for a symbol, a scheme-indent-function property is also
considered, although the “with-” indents defined by scheme-mode
are ignored. This is only to help people who may have extensive
scheme-indent-function settings, particularly in the form of file
or dir local variables. Otherwise prefer putting properties on
racket-indent-function
.
If no explicit rules match, regular expressions are used for a couple special cases:
On the one hand this is convenient when you create your own “DRY” macros; they will indent as expected without you needing to make custom indent rules. On the other hand there can be false matches; for example a function or form named “defer” will indent like “define”. This is a known drawback and is unlikely to be fixed unless/until Racket macros someday support a protocol to communicate how they should be indented.
There is also automatic handling for:
Finally and otherwise, a form will be indented as if it were a procedure application.
— — —
Note: Racket Mode extends the traditional Emacs lisp indent spec to allow a negative integer, which means that all distinguished forms should align with the first one. This style originated with “for/fold”, which has two distinguished forms. Traditionally those would indent like this:
(for/fold ([x xs]) ([y ys]) ; twice body indent body)
However the popularly desired indent is:
(for/fold ([x xs]) ([y ys]) ; same as first distingushed form body)
This idea extends to optional distinguished forms, such as Typed Racket annotation “prefixes” in “for/fold”, “for/x”, and even “let” forms:
(for/fold : Type ([x xs]) ([y ys]) ; same as first distingushed form body)
M-x racket-smart-open-bracket-mode
Minor mode to let you always type [
’ to insert (
or [
automatically.
Behaves like the “Automatically adjust opening square brackets” feature in Dr. Racket.
By default, inserts a (
. Inserts a [
in the following cases:
let
-like bindings – forms with let
in the name as well
as things like parameterize
, with-handlers
, and
with-syntax
.
case
, cond
, match
, syntax-case
, syntax-parse
, and
syntax-rules
clauses.
for
-like bindings and for/fold
accumulators.
class
declaration syntax, such as init
and inherit
.
When the previous s-expression in a sequence is a compound expression, uses the same kind of delimiter.
To force insert [
, use quoted-insert
.
Combined with racket-insert-closing this means that you can
press the unshifted [
and ]
keys to get whatever delimiters
follow the Racket conventions for these forms. When something
like electric-pair-mode
or paredit-mode
is active, you need
not even press ]
.
Tip: When also using paredit-mode
, enable that first so that
the binding for the [
’ key in the map for
racket-smart-open-bracket-mode has higher priority. See also
the variable minor-mode-map-alist
.
Tip: When using this with racket-hash-lang-mode, you may want to use racket-hash-lang-module-language-hook to enable it IFF the module langugage is something like “racket”.
This is a minor mode. If called interactively, toggle the
Racket-Smart-Open-Bracket mode
mode. If the prefix argument is
positive, enable the mode, and if it is zero or negative, disable
the mode.
If called from Lisp, toggle the mode if ARG is toggle
. Enable
the mode if ARG is nil, omitted, or is a positive number.
Disable the mode if ARG is a negative number.
To check whether the minor mode is enabled in the current buffer, evaluate racket-smart-open-bracket-mode.
The mode’s hook is called both when the mode is enabled and when it is disabled.
] or )
Insert a matching closing delimiter.
With C-u insert the typed character as-is.
This is handy if you’re not yet using something like
paredit-mode
, smartparens-mode
, parinfer-mode
, or simply
electric-pair-mode
added in Emacs 24.5.
C-M-u
Like backward-up-list
but works when point is in a string or comment.
Typically you should not use this command in Emacs Lisp –
especially not repeatedly. Instead, initially use
racket--escape-string-or-comment
to move to the start of a
string or comment, if any, then use normal backward-up-list
repeatedly.
M-x racket-unicode-input-method-enable
Set input method to racket-unicode.
The racket-unicode input method lets you easily type various Unicode symbols that might be useful when writing Racket code.
To automatically enable the racket-unicode input method in racket-mode and racket-repl-mode buffers, put the following code in your Emacs init file:
(add-hook 'racket-mode-hook #'racket-unicode-input-method-enable) (add-hook 'racket-repl-mode-hook #'racket-unicode-input-method-enable)
To temporarily enable this input method for a single buffer you can use “M-x racket-unicode-input-method-enable”.
Use the standard Emacs key C-\ to toggle the input method.
When the racket-unicode input method is active, you can for example type “All” and it is immediately replaced with “∀”. A few other examples:
omega | ω |
x_1 | x₁ |
x^1 | x¹ |
A | 𝔸 |
test–>>E | test–>>∃ (racket/redex) |
vdash | ⊢ |
To see a table of all key sequences use “M-x describe-input-method <RET> racket-unicode”.
If you want to add your own mappings to the “racket-unicode” input method, you may add code like the following example in your Emacs init file:
;; Either (require 'racket-mode) here, or, if you use ;; use-package, put the code below in the :config section. (with-temp-buffer (racket-unicode-input-method-enable) (set-input-method "racket-unicode") (let ((quail-current-package (assoc "racket-unicode" quail-package-alist))) (quail-define-rules ((append . t)) ("^o" ["ᵒ"]))))
If you don’t like the highlighting of partially matching tokens you
can turn it off by setting input-method-highlight-flag
to nil.
M-x racket-align
Align values in the same column.
Useful for binding forms like “let” and “parameterize”, conditionals like “cond” and “match”, association lists, and any series of couples like the arguments to “hash”.
Before choosing this command, put point on the first of a series of “couples”. A couple is:
Each “val” moves to the same column and is
prog-indent-sexp
-ed (in case it is a multi-line form).
For example with point on the “[” before “a”:
Before After (let ([a 12] (let ([a 12] [bar 23]) [bar 23]) ....) ....) ([a . 12] ([a . 12] [bar . 23]) [bar . 23]) (cond [a? #t] (cond [a? #t] [b? (f x [b? (f x y)] y)] [else #f]) [else #f])
Or with point on the quote before “a”:
(list a 12 (list a 12 bar 23) bar 23)
If more than one couple is on the same line, none are aligned, because it is unclear where the value column should be. For example the following form will not change; racket-align will display an error message:
(let ([a 0][b 1] [c 2]) error; unchanged ....)
When a couple’s sexprs start on different lines, that couple is ignored. Other, single-line couples in the series are aligned as usual. For example:
(let ([foo (let ([foo 0] 0] [bar 1] [bar 1] [x 2]) [x 2]) ....) ....)
See also: racket-unalign.
M-x racket-unalign
The opposite of racket-align.
Effectively does M-x just-one-space
and prog-indent-sexp
for
each couple’s value.
A value for the variable completion-at-point-functions
.
Completion candidates are drawn from the same symbols used for font-lock. This is a static list. If you want dynamic, smarter completion candidates, enable the minor mode racket-xp-mode.
M-x racket-hash-lang-mode
Use color-lexer, indent, and navigation supplied by a #lang.
An experimental major mode alternative to racket-mode for source file edit buffers.
In your Emacs configuration, you may want to update the
variable auto-mode-alist
to use racket-hash-lang-mode for
file extensions like “.rkt”, “.scrbl”, and/or “.rhm”.
Languages supply colors for lexer tokens like strings and comments; see the customization variable racket-hash-lang-token-face-alist. For more colors see the hook variable racket-hash-lang-module-language-hook, which can also be used to vary configurations per language.
A discussion of the information provided by a Racket language:
https://docs.racket-lang.org/tools/lang-languages-customization.html
Key | Binding |
DEL | racket-hash-lang-delete-backward-char |
RET | newline-and-indent |
TAB | indent-for-tab-command |
C-x C-e | racket-send-last-sexp |
C-M-q | racket-hash-lang-C-M-q-dwim |
C-M-d | racket-hash-lang-down |
C-M-u | racket-hash-lang-up |
C-M-f | racket-hash-lang-forward |
C-M-b | racket-hash-lang-backward |
C-M-y | racket-insert-lambda |
C-M-x | racket-send-definition |
C-c C-u | racket-unfold-all-tests |
C-c C-f | racket-fold-all-tests |
C-c C-x C-f | racket-open-require-path |
C-c C-e r | racket-expand-region |
C-c C-e e | racket-expand-last-sexp |
C-c C-e x | racket-expand-definition |
C-c C-e f | racket-expand-file |
C-c C-r | racket-send-region |
C-c C-o | racket-profile |
C-c C-l | racket-logger |
C-c C-t | racket-test |
C-c C-z | racket-edit-switch-to-repl |
C-c C-k | racket-run-module-at-point |
C-c C-c | racket-run-module-at-point |
In addition to any hooks its parent mode prog-mode
might have run,
this mode runs the hook racket-hash-lang-mode-hook
, as the final or
penultimate step during initialization.
C-M-q
Fill or indent depending on lang lexer’s token at point.
When the lang lexer token is…
fill-paragraph
.
fill-comment
.
prog-indent-sexp
.
M-x racket-xp-mode
A minor mode that analyzes expanded code to explain and explore.
This minor mode is an optional enhancement to racket-mode edit buffers. Like any minor mode, you can turn it on or off for a specific buffer. If you always want to use it, put the following code in your Emacs init file:
(require 'racket-xp) (add-hook 'racket-mode-hook #'racket-xp-mode)
Note: This mode won’t do anything unless/until the Racket Mode back end is running. It will try to start the back end automatically. You do not need to racket-run the buffer you are editing.
This mode uses the drracket/check-syntax package to analyze fully-expanded programs, without needing to evaluate a.k.a. “run” them. The resulting analysis provides information for:
When point is on a definition or use, related items are highlighted using racket-xp-def-face and racket-xp-use-face – instead of drawing arrows as in Dr Racket. Information is displayed using the function(s) in the hook variable racket-show-functions; it is also available when hovering the mouse cursor.
Note: If you find these point-motion features too distracting
and/or slow, in your racket-xp-mode-hook
you may disable them:
(require 'racket-xp) (add-hook 'racket-xp-mode-hook (lambda () (remove-hook 'pre-redisplay-functions #'racket-xp-pre-redisplay t)))
The remaining features discussed below will still work.
You may also use commands to navigate among a definition and its uses, or to rename a local definitions and all its uses:
In the following little example, not only does drracket/check-syntax distinguish the various “x” bindings, it understands the two different imports of “define”:
#lang racket/base (define x 1) x (let ([x x]) (+ x 1)) (module m typed/racket/base (define x 2) x)
When point is on the opening parenthesis of an expression in tail position, it is highlighted using the face racket-xp-tail-position-face.
When point is on the opening parenthesis of an enclosing expression with respect to which one or more expressions are in tail position, it is highlighted using the face racket-xp-tail-target-face.
Furthermore, when point is on the opening parenthesis of either kind of expression, all of the immediately related expressions are also highlighted. Various commands move among them:
The function racket-xp-complete-at-point
is added to the
variable completion-at-point-functions
. Note that in this case,
it is not smart about submodules; identifiers are assumed to be
definitions from the file’s module or its imports. In addition to
supplying completion candidates, it supports the
“:company-location” property to inspect the definition of a
candidate and the “:company-doc-buffer” property to view its
documentation.
When you edit the buffer, existing annotations are retained; their positions are updated to reflect the edit. Annotations for new or deleted text are not requested until after racket-xp-after-change-refresh-delay seconds. The request is made asynchronously so that Emacs will not block – for moderately complex source files, it can take some seconds simply to fully expand them, as well as a little more time for the drracket/check-syntax analysis. When the results are ready, all annotations for the buffer are completely refreshed.
You may also set racket-xp-after-change-refresh-delay to nil
and use the racket-xp-annotate
command manually.
The mode line changes to reflect the current status of annotations, and whether or not you had a syntax error.
If you have one or more syntax errors, next-error
and
previous-error
navigate among them. Although most languages
will stop after the first syntax error, some like Typed Racket
will try to collect and report multiple errors.
You may use xref-find-definitions
M-. ,
xref-pop-marker-stack
M-x xref-pop-marker-stack
, and
xref-find-references
: racket-xp-mode adds a backend to the
variable xref-backend-functions
. This backend uses information
from the drracket/check-syntax static analysis. Its ability to
find references is limited to the current file; when it finds
none it will try the default xref backend implementation which is
grep-based.
Tip: This mode follows the convention that a minor mode may only
use a prefix key consisting of “C-c” followed by a punctuation
key. As a result, racket-xp-control-c-hash-keymap
is bound to
“C-c #” by default. Although you might find this awkward to
type, remember that as an Emacs user, you are free to bind this
map to a more convenient prefix, and/or bind any individual
commands directly to whatever keys you prefer.
Key | Binding |
M-. | xref-find-definitions |
C-c C-s | racket-describe-search |
C-c C-d | racket-xp-documentation |
C-c C-. | racket-xp-describe |
C-c # P | previous-error |
C-c # N | next-error |
C-c # g | racket-xp-annotate |
C-c # < | racket-xp-tail-previous-sibling |
C-c # > | racket-xp-tail-next-sibling |
C-c # v | racket-xp-tail-down |
C-c # ^ | racket-xp-tail-up |
C-c # r | racket-xp-rename |
C-c # ? | xref-find-references |
C-c # . | xref-find-definitions |
C-c # p | racket-xp-previous-use |
C-c # n | racket-xp-next-use |
C-c # k | racket-xp-previous-definition |
C-c # j | racket-xp-next-definition |
This is a minor mode. If called interactively, toggle the
Racket-Xp mode
mode. If the prefix argument is positive,
enable the mode, and if it is zero or negative, disable the mode.
If called from Lisp, toggle the mode if ARG is toggle
. Enable
the mode if ARG is nil, omitted, or is a positive number.
Disable the mode if ARG is a negative number.
To check whether the minor mode is enabled in the current buffer, evaluate racket-xp-mode.
The mode’s hook is called both when the mode is enabled and when it is disabled.
C-c C-.
Describe the identifier at point.
The command varies based on how many C-u command prefixes you supply.
Uses the symbol at point. If no such symbol exists, you are prompted enter the identifier, but in this case it only considers definitions or imports at the file’s module level – not local bindings nor definitions in submodules.
Always prompts you to enter a symbol, defaulting to the symbol at point if any.
This is an alias for racket-describe-search, which uses
installed documentation in a racket-describe-mode
buffer
instead of an external web browser.
The intent is to give a quick reminder or introduction to something, regardless of whether it has installed documentation – and to do so within Emacs, without switching to a web browser.
This buffer is also displayed when you use company-mode
and
press F1 or C-h in its pop up completion list.
C-c C-d
View documentation in an external web browser.
The command varies based on how many C-u command prefixes you supply.
Uses the symbol at point. Tries to find documentation for an identifer defined in the expansion of the current buffer.
If no such identifer exists, opens the Search Manuals page. In
this case, the variable racket-documentation-search-location
determines whether the search is done locally as with raco
doc
, or visits a URL.
Always prompts you to enter a symbol, defaulting to the symbol at point if any.
Always prompts you to enter anything, defaulting to the symbol at point if any.
Proceeds directly to the Search Manuals page. Use this if you would like to see documentation for all identifiers named “define”, for example.
C-c # ^
Go “up” to the expression enclosing an expression in tail position.
When point is on the opening parenthesis of an expression in tail position, go its “target” – that is, go to the enclosing expression with the same continuation as the tail expression.
C-c # v
Go “down” to the first tail position enclosed by the current expression.
C-c # >
Go to the next tail position sharing the same enclosing expression.
C-c # <
Go to the previous tail position sharing the same enclosing expression.
C-c C-d
Search documentation.
This command is useful in several situations:
This command does not try to go directly to the help topic for a definition provided by any specific module. Instead it goes to the Racket “Search Manuals” page.
C-c C-. or C-c C-s
Search installed documentation; view using racket-describe-mode
.
Always prompts you to enter a symbol, defaulting to the symbol at point if any.
M-x racket-repl-mode
Major mode for Racket REPL.
You may use xref-find-definitions
M-. and
xref-pop-marker-stack
M-x xref-pop-marker-stack
:
racket-repl-mode adds a backend to the variable
xref-backend-functions
. This backend uses information about
identifier bindings and modules from the REPL’s namespace.
Key | Binding |
} | racket-insert-closing |
] | racket-insert-closing |
) | racket-insert-closing |
C-c C-\ | racket-repl-exit |
C-c C-c | racket-repl-break |
C-c C-l | racket-logger |
C-c C-z | racket-repl-switch-to-edit |
C-c C-s | racket-describe-search |
C-c C-. | racket-repl-describe |
C-c C-d | racket-repl-documentation |
C-c C-e r | racket-expand-region |
C-c C-e e | racket-expand-last-sexp |
C-c C-e x | racket-expand-definition |
C-c C-e f | racket-expand-file |
C-c C-o | racket-repl-delete-output |
C-c C-n | racket-repl-next-prompt-or-run |
C-c C-p | racket-repl-previous-prompt-or-run |
C-c C-u | racket-repl-clear-input |
C-M-y | racket-insert-lambda |
M-n | racket-repl-next-input |
M-p | racket-repl-previous-input |
C-M-q | prog-indent-sexp |
C-M-u | racket-backward-up-list |
TAB | indent-for-tab-command |
C-j | newline-and-indent |
RET | racket-repl-submit |
This mode runs the hook racket-repl-mode-hook
, as the final or
penultimate step during initialization.
M-x racket-run
Save the buffer in REPL and run your program.
As well as evaluating the outermost, file module, automatically runs the submodules specified by the customization variable racket-submodules-to-run.
See also racket-run-module-at-point, which runs just the specific module at point.
The command varies based on how many C-u prefix arguments you supply.
Follows the racket-error-context setting.
Uses errortrace for improved stack traces, as if racket-error-context were set to “high”.
This lets you keep racket-error-context set to a faster value like “low” or “medium”, then conveniently re-run when you need a better strack trace.
Instruments code for step debugging. See racket-debug-mode and the variable racket-debuggable-files.
Each run occurs within a Racket custodian. Any prior run’s custodian is shut down, releasing resources like threads and ports. Each run’s evaluation environment is reset to the contents of the source file. In other words, like Dr Racket, this provides the benefit that your source file is the “single source of truth”. At the same time, the run gives you a REPL inside the namespace of the module, giving you the ability to explore it interactively. Any explorations are temporary, unless you also make them to your source file, they will be lost on the next run.
See also racket-run-and-switch-to-repl, which is even more like Dr Racket’s Run command because it selects the REPL window after running.
To visit error locations, move point there and press RET or mouse
click. Or, use the standard next-error
and previous-error
commands from either the edit or REPL buffer.
<f5>
This is racket-run followed by selecting the REPL buffer window.
This is similar to how Dr Racket behaves.
To make it even more similar, you may add racket-repl-clear to the variable racket-before-run-hook.
C-c C-k or C-c C-c
Save the buffer and run the module at point.
Like racket-run but runs the innermost module around point, which is determined textually by looking for “module”, “module*”, or “module+” forms nested to any depth, else simply the outermost, file module.
M-x racket-repl
Show a Racket REPL buffer in some window.
The intended use of Racket Mode’s REPL is that you find-file
some specific file, then run it using a command like racket-run
or racket-run-module-at-point. The resulting REPL will
correspond to those definitions and match your expectations.
Therefore this racket-repl command – which is intended as a convenience for people who want to “just get a quick scratch REPL” – is actually implemented as running the file named in the customization variable racket-repl-command-file. When that file doesn’t exist, it is created to contain just “#lang racket/base”. You may edit the file to use a different lang, require other modules, or whatever.
C-c C-.
Describe the identifier at point.
The command varies based on how many C-u prefix arguments you supply.
Uses the symbol at point. If no such symbol exists, you are prompted enter the identifier, but in this case it only considers definitions or imports at the file’s module level – not local bindings nor definitions in submodules.
Always prompts you to enter a symbol, defaulting to the symbol at point if any.
This is an alias for racket-describe-search, which uses
installed documentation in a racket-describe-mode
buffer
instead of an external web browser.
The intent is to give a quick reminder or introduction to something, regardless of whether it has installed documentation – and to do so within Emacs, without switching to a web browser.
C-c C-d
View documentation in an external web browser.
The command varies based on how many C-u command prefixes you supply.
Uses the symbol at point. Tries to find documentation for an identifer defined in the current namespace.
If no such identifer exists, opens the Search Manuals page. In
this case, the variable racket-documentation-search-location
determines whether the search is done locally as with raco
doc
, or visits a URL.
Prompts you to enter a symbol, defaulting to the symbol at point if any.
Prompts you to enter anything, defaulting to the symbol at point if any.
Proceeds directly to the Search Manuals page. Use this if you would like to see documentation for all identifiers named “define”, for example.
C-M-<f5>
Use command-line racket to run the file.
Uses a shell or terminal buffer as specified by the configuration variable racket-shell-or-terminal-function.
C-c C-o
Like racket-run-module-at-point but with profiling.
Results are presented in a racket-profile-mode buffer, which also lets you quickly view the source code.
You may evaluate expressions in the REPL. They are also profiled.
Use racket-profile-refresh
to see the updated results. In
other words a possible workflow is: racket-profile a .rkt file,
call one its functions in the REPL, and refresh the profile
results.
Caveat: Only source files are instrumented. You may need to delete compiled/*.zo files.
M-x racket-profile-mode
Major mode for results of racket-profile.
Key | Binding |
RET | racket-profile-visit |
. | racket-profile-visit |
f | racket-profile-show-non-project |
z | racket-profile-show-zero |
g | racket-profile-refresh |
q | quit-window |
In addition to any hooks its parent mode tabulated-list-mode
might
have run, this mode runs the hook racket-profile-mode-hook
, as the
final or penultimate step during initialization.
M-x racket-logger-mode
Major mode for Racket logger output.
The customization variable racket-logger-config determines the
levels for topics. During a session you may change topic levels
using racket-logger-topic-level
.
For more information see: https://docs.racket-lang.org/reference/logging.html
Key | Binding |
g | racket-logger-clear |
p | racket-logger-previous-item |
n | racket-logger-next-item |
w | toggle-truncate-lines |
l | racket-logger-topic-level |
In addition to any hooks its parent mode special-mode
might have
run, this mode runs the hook racket-logger-mode-hook
, as the final
or penultimate step during initialization.
M-x racket-debug-mode
Minor mode for debug breaks.
This feature is EXPERIMENTAL!!! It is likely to have significant limitations and bugs. You are welcome to open an issue to provide feedback. Please understand that this feature might never be improved – it might even be removed someday if it turns out to have too little value and/or too much cost.
How to debug:
Use two C-u command prefixes for either racket-run or racket-run-module-at-point.
The file will be instrumented for step debugging before it is run. Any imported files are also instrumented if they are in the variable racket-debuggable-files.
The run will break at the first breakable position.
Tip: After you run to completion and return to a normal REPL prompt, the code remains instrumented. You may enter expressions that evaluate instrumented code and it will break so you can step debug again.
set!
.
Also, in the racket-mode buffer where the break is located, racket-debug-mode is enabled. This minor mode makes the buffer read-only, provides visual feedback – about the break position, local variable values, and result values – and provides shortcut keys:
Key | Binding |
? | racket-debug-help |
h | racket-debug-run-to-here |
! | racket-debug-toggle-breakpoint |
P | racket-debug-prev-breakpoint |
N | racket-debug-next-breakpoint |
p | racket-debug-prev-breakable |
n | racket-debug-next-breakable |
g | racket-debug-go |
c | racket-debug-continue |
u | racket-debug-step-out |
o | racket-debug-step-over |
SPC | racket-debug-step |
This is a minor mode. If called interactively, toggle the
Racket-Debug mode
mode. If the prefix argument is positive,
enable the mode, and if it is zero or negative, disable the mode.
If called from Lisp, toggle the mode if ARG is toggle
. Enable
the mode if ARG is nil, omitted, or is a positive number.
Disable the mode if ARG is a negative number.
To check whether the minor mode is enabled in the current buffer, evaluate racket-debug-mode.
The mode’s hook is called both when the mode is enabled and when it is disabled.
Delete all text in the REPL.
A suitable value for the hook racket-before-run-hook if you
want the REPL buffer to be cleared before each run, much like
with Dr Racket. To do so you can use customize
, or, add to your
Emacs init file something like:
(add-hook ’racket-before-run-hook #’racket-repl-clear)
See also the command racket-repl-clear-leaving-last-prompt.
M-x racket-repl-clear-leaving-last-prompt
Delete all text in the REPL, except for the last prompt.
C-<f5> or C-c C-t
Run the “test” submodule.
Put your tests in a “test” submodule. For example:
(module+ test (require rackunit) (check-true #t))
Any rackunit test failure messages show the location. You may use
next-error
to jump to the location of each failing test.
With C-u uses errortrace for improved stack traces. Otherwise follows the racket-error-context setting.
With C-u C-u also runs the
tests with coverage instrumentation and highlights uncovered code
using font-lock-warning-face
.
See also:
M-x racket-raco-test
Use command-line raco test to run the “test” submodule.
Uses a shell or terminal buffer as specified by the configuration variable racket-shell-or-terminal-function.
C-x C-e
Send the expression before point to the Racket REPL.
The expression may be either an at-expression or an s-expression.
When the expression is a sexp comment, the sexp itself is sent, without the #; prefix.
With a prefix argument (e.g. C-u C-x C-e ), the sexp is copied into the REPL, followed by a “=>” line, to distinguish it from the zero or more values to which it evaluates.
C-c C-x C-f
Like Dr Racket’s Open Require Path.
Type (or delete) characters that are part of a module path name. “Fuzzy” matches appear. For example try typing “t/t/r”.
Choices are displayed in a vertical list. The current choice is at the top, marked with “->”.
find-file
.
M-x racket-stepper-mode
Major mode for Racket stepper output.
Used by the commands racket-expand-file, racket-expand-definition, racket-expand-region, and racket-expand-last-sexp.
Key | Binding |
g | racket-stepper-refresh |
k | racket-stepper-previous-item |
p | racket-stepper-previous-item |
j | racket-stepper-next-item |
n | racket-stepper-next-item |
RET | racket-stepper-step |
In addition to any hooks its parent mode special-mode
might have
run, this mode runs the hook racket-stepper-mode-hook
, as the final
or penultimate step during initialization.
C-c C-e f
Expand the racket-mode buffer’s file in racket-stepper-mode.
Uses the macro-debugger
package to do the expansion.
You do not need to racket-run the file first; the namespace active in the REPL is not used.
If the file is non-trivial and/or is not compiled to a .zo bytecode file, then it might take many seconds before the original form is displayed and you can start stepping.
With C-u behaves as if racket-expand-hiding were ’disabled.
C-c C-e r
Expand the active region using racket-stepper-mode.
Uses the macro-debugger
package to do the expansion.
With C-u behaves as if racket-expand-hiding were ’disabled.
C-c C-e x
Expand the definition around point using racket-stepper-mode.
Uses the macro-debugger
package to do the expansion.
With C-u behaves as if racket-expand-hiding were ’disabled.
C-c C-e e
Expand the sexp before point using racket-stepper-mode.
Uses the macro-debugger
package to do the expansion.
With C-u behaves as if racket-expand-hiding were ’disabled.
M-x racket-package-refresh
Refresh the local copy of package catalogs.
Will make HTTP requests to remote catalog servers. May take a few seconds to complete.
M-x list-racket-packages
Open a racket-package-mode buffer for the active back end.
M-x racket-package-mode
Major mode for Racket package management.
The list of packages is equivalent to “raco pkg show -all” on the active back end – that is, all packages installed manually or as dependencies – plus packages available from your configured catalogs, assuming you have run the command racket-package-refresh.
On each row you can press RET to describe-racket-package
, which
opens a buffer where you can view details, and use buttons to
install/update/remove the package.
Key | Binding |
RET | racket-package-describe |
In addition to any hooks its parent mode tabulated-list-mode
might
have run, this mode runs the hook racket-package-mode-hook
, as the
final or penultimate step during initialization.
M-x describe-racket-package
Describe details of a Racket package.
Depending on the package status, buttons let you install, update, and/or remove the package and its dependencies. These convenience buttons are equivalent to using the command line on the active back end to do “raco pkg {install update remove} –auto”. For other operations, you still need to use “raco pkg” yourself; see https://docs.racket-lang.org/pkg/cmdline.html.
Detail values are links when possible:
If the package is available from a catalog, additional details will be shown, assuming you have run the command racket-package-refresh.
M-x racket-debug-toggle-breakpoint
Add or remove a breakpoint.
Each breakpoint has a condition and a list of actions.
The condition is a Racket expression that is evaluated in a context where local variables exist. Examples:
Actions is a list of symbols; you may specify one or more. The action symbols are:
Note: Although racket-debug-mode provides a convenient keybinding, you may invoke this command anytime using M-x.
Note: If you’re warned that point isn’t known to be a breakable position, that might be because it truly isn’t, or, just because you are not in racket-debug-mode and the breakable positions aren’t yet known. Worst case, if you set a breakpoint someplace that is not breakable, it is ignored. With a few exceptions – such as close paren positions that are tail calls – most open parens and close parens are breakble positions.
M-x racket-mode-start-faster
Compile Racket Mode’s .rkt files for faster startup.
Racket Mode is implemented as an Emacs Lisp “front end” that
talks to a Racket process “back end”. Because Racket Mode is
delivered as an Emacs package instead of a Racket package,
installing it does not do the raco setup
that is normally done
for Racket packages.
This command will do a raco make
of Racket Mode’s .rkt files,
creating bytecode files in compiled/
subdirectories. As a
result, when a command must start the Racket process, it will
start somewhat faster.
On many computers, the resulting speed up is negligible, and might not be worth the complication.
If you run this command, ever, you will need to run it again after:
To revert to compiling on startup, use racket-mode-start-slower.
M-x racket-mode-start-slower
Delete the “compiled” directories made by racket-mode-start-faster.
Pathname of the Racket executable.
Note that a back end configuration can override this with a
non-nil racket-program
property list value. See
racket-add-back-end.
How many seconds to wait for command server responses.
Note: This is mostly obsolete, fortunately, because it applies only to commands that must block the Emacs UI until they get a response. Instead most Racket Mode commands these days receive their response asychronously.
Terminate the Racket process if memory use exceeds this value in MB.
Changes to this value take effect upon the next racket-run. A value of 0 means no limit.
Caveat: This uses Racket’s custodian-limit-memory
, which does
not enforce the limit exactly. Instead, the program will be
terminated upon the first garbage collection where memory exceeds
the limit (maybe by a significant amount).
The amount of context for error messages.
Each increasing level supplies better context (“stack trace”) for error messages, but causing your program to run more slowly.
Tip: Regardless of this setting, you can enable high errortrace for a specific racket-run or racket-run-module-at-point by using C-u . This lets you normally run with a lower, faster setting, and re-run when desired to get a more-helpful error message.
List of command-line arguments to supply to your Racket program.
Accessible in your Racket program in the usual way — the
parameter current-command-line-arguments
and friends.
This is an Emacs buffer-local variable — convenient to set as a file local variable. For example at the end of your .rkt file:
;; Local Variables: ;; racket-user-command-line-arguments: ("-f" "bar") ;; End:
Set this way, the value must be an unquoted list of strings. For example:
("-f" "bar")
The following values will not work:
'("-f" "bar") (list "-f" "bar")
Function to call to browse a URL.
Defaults to racket-browse-url-using-temporary-file on macOS and
browse-url-browser-function
on other platforms.
Seconds to wait before refreshing racket-xp-mode annotations.
Set to nil to disable automatic refresh and manually use racket-xp-annotate
.
Only give racket-xp-unused-face to unused bindings that match this regexp.
The default is to highlight identifiers that do not start with an underline, which is a common convention.
Have racket-xp-mode fontify binding identifier sites.
A ’font-lock-face property is added for bindings from:
This has a visible effect only when there is not also a ’face property applied by the major mode’s fontification.
How much documentation to show via eldoc
.
Used by racket-xp-eldoc-point
and racket-xp-eldoc-sexp-app
.
A third-party package like eldoc-box
can be useful for all but
the minimal level. Even some bluebox signatures can take many
lines to show on screen.
The location of the Racket “Search Manuals” web page. Where racket-documentation-search, racket-xp-documentation and racket-repl-documentation should look for the search page.
format
, with
“%s” at the point at which to insert the user’s search text
after applying url-hexify-string
. Apart from “%s”, the
string should be a properly encoded URL.
An association list from color-lexer token symbols to face symbols.
Note: In many Racket languages, the lexer classifies tokens for identifiers as ’symbol. In many programs, a majority of the source consists of identifiers at binding definition and use sites. Therefore the appearance of “symbol” tokens is significant, and a matter of personal preference.
Note: Some tokens are hardwired and not customizable by this
list: Comment tokens use the face font-lock-comment-face
,
sometimes blended with other faces. Parenthesis tokens use the
face parenthesis
if defined, as by the paren-face package.
String tokens use font-lock-string-face
. Text tokens, e.g.
Scribble text, use the face racket-hash-lang-text.
Pairs of delimiters to insert or delete automatically.
The format of each item is (cons string string).
This is initialized whenever a module language changes, using values from the language’s reported values for drracket:paren-matches and drracket:quote-matches.
You may customize this default initialization in racket-hash-lang-module-language-hook.
Hook run when the module language changes.
Typically in Emacs each language gets its own major mode. As a
result, the major mode hook is your opportunity to express
preferences. However racket-hash-lang-mode handles radically
different kinds of hash langs in one major mode. And a given
buffer can change langs when you edit the “#lang” line. As a
result, racket-hash-lang-mode-hook
is not useful for per-lang
configuration. Instead you need a kind of “sub major mode
hook”. This is that hook.
The hook is run when a file is first visited, and thereafter whenever the “#lang” line is edited – provided that results in different language info; for example changing from “#lang racket” to “#lang racket/base” will not run the hook.
The function is called with a string returned by the lang’s “module-language” info key. This info key is supplied automatically when a language is defined using syntax/module-reader:
https://docs.racket-lang.org/syntax/reader-helpers.html#%28mod-path._syntax%2Fmodule-reader%29.
Otherwise a lang might not supply this and the value will be nil.
The hook is useful when you want to vary Emacs behavior in ways that go beyond what a lang can describe. This may include enabling “fancy” or “classic” Emacs behaviors only for s-expression langs.
For example, maybe you want to use paredit-mode
when it is
suitable for the module language:
(defun my-hook (module-language) (let ((rackety (member module-language (list "racket" "racket/base" "typed/racket" "typed/racket/base")))) (if rackety (paredit-mode 1) (paredit-mode -1)))) (add-hook 'racket-hash-lang-module-language-hook #'my-hook)
A similar tactic can be used for smartparens
or
electric-pair-mode
. In general, none of these
delimiter-matching modes is likely to work well unless the
hash-lang uses racket for drracket:grouping-position, in which
case racket-hash-lang-mode uses the classic racket-mode
syntax-table for the buffer. Otherwise you should not enable one
of these modes, and instead just use the simple delimiter
matching built into racket-hash-lang-mode; see
racket-hash-lang-pairs.
As another example, if you prefer more colors than just tokens, choices include:
racket-hash-lang-mode-hook
and in
the module language hook locally set
racket-xp-add-binding-faces:
(setq-local racket-xp-add-binding-faces t)
OR
(require 'racket-font-lock) (if rackety (font-lock-add-keywords nil (append racket-font-lock-keywords-2 racket-font-lock-keywords-3)) (font-lock-remove-keywords nil (append racket-font-lock-keywords-2 racket-font-lock-keywords-3)))
How to associate racket-mode edit buffers with racket-repl-mode buffers.
The default is nil, which is equivalent to supplying racket-repl-buffer-name-shared: One REPL buffer is shared.
Other predefined choices include racket-repl-buffer-name-unique and racket-repl-buffer-name-project.
This is used when a racket-mode buffer is created. Changing this to a new value only affects racket-mode buffers created later.
Any such function takes no arguments, should look at the variable
buffer-file-name
if necessary, and either setq-default
or
setq-local
the variable racket-repl-buffer-name
to a desired
racket-repl-mode buffer name. As a result, racket-run
commands will use a buffer of that name, creating it if
necessary.
Extra submodules to run.
This is a list of submodules. Each submodule is described as a list, to support submodules nested to any depth.
This is used by commands that emulate the DrRacket Run command:
It is NOT used by commands that run one specific module, such as:
Input matching this regexp are NOT saved on the history list. Default value is a regexp to ignore input that is all whitespace.
Use ImageMagick with these properties for REPL images.
When this property list is not empty – and the variable
racket-images-inline is true, and Emacs is built with with
ImageMagick support – then create-image
is called with
“imagemagick” as the type and with this property list.
For example, to scale images whose width is larger than 500 pixels, supply (:max-width 500).
Do not use SVG to render images?
Note: This value is used only when starting a back end – not
for each run. If you change this, for it to take effect you must
restart by using racket-start-back-end
.
Indent {}
with items aligned with the head item?
This is indirectly disabled if racket-indent-sequence-depth is 0. This is safe to set as a file-local variable.
To what depth should racket-indent-line search.
This affects the indentation of forms like ’() ‘() #() –
and {} if racket-indent-curly-as-sequence is t — but not
#’() #‘() ,() ,@(). A zero value disables, giving the
normal indent behavior of DrRacket or Emacs lisp-mode
derived
modes like scheme-mode
. Setting this to a high value can make
indentation noticeably slower. This is safe to set as a
file-local variable.
Display lambda keywords using λ. This is DEPRECATED.
Instead use prettify-symbols-mode
in newer verisons of Emacs,
or, use racket-insert-lambda to insert actual λ characters.
This variable is obsolete and has no effect.
Instead of using this variable, you may bind the [
key to the
racket-smart-open-bracket
command in the racket-mode-map
and/or racket-repl-mode-map
keymaps.
Configuration of racket-logger-mode topics and levels.
The topic “*” respresents the default level used for topics not
assigned a level. Otherwise, the topic symbols are the same as
used by Racket’s define-logger
.
The levels are those used by Racket’s logging system: “debug”, “info”, “warning”, “error”, “fatal”.
For more information see: https://docs.racket-lang.org/reference/logging.html
The default value sets some known “noisy” topics to be one level quieter. That way you can set the “*” topic to a level like “debug” and not get overhwelmed by these noisy topics.
Normal hook done before various Racket Mode run commands.
Here “before” means that the racket-repl-mode buffer might not exist yet.
When hook functions are called, current-buffer
is that of the
edit buffer when the run command was issued. If a hook function
instead needs the racket-repl-mode buffer, it should get that
from the variable racket-repl-buffer-name
.
Normal hook done after various Racket Mode run commands.
Here “after” means that the run has completed and the REPL is waiting at another prompt.
When hook functions are called, current-buffer
is that of the
buffer when the run command was issued. If a hook function
instead needs the racket-repl-mode buffer, it should get that
from the variable racket-repl-buffer-name
.
How much to fade faces used in s-expression comment bodies.
A number from 0.0 to 1.0, where 0.0 is 0% fade and 1.0 is 100% fade (invisible).
This feature works by creating faces that are alternatives for
faces used in s-expression comments. The alernative faces use a
faded foreground color. The colors are recalculated automatically
after you change the value of this customization variable and
after any load-theme
. However in other circumstances you might
need to use racket-refresh-sexp-comment-faces
.
Used to tell racket-run what files may be instrumented for debugging.
This isn’t yet a defcustom becuase the debugger status is still “experimental”.
Must be either a list of file name strings, or, a function that takes the name of the file being run and returns a list of file names.
Each file name in the list is made absolute using
expand-file-name
with respect to the file being run and given
to racket-file-name-front-to-back
.
An “abnormal hook” variable to customize racket-show
.
This is a list of one or more functions.
Each such function must accept two arguments: STR and POS.
STR is one of:
POS may be nil when STR is nil or a blank string.
Otherwise POS is the buffer position – typically the end of a span – that the non-blank STR describes.
A function that shows STR near POS should position it not to hide the span, i.e. below and/or right of POS. Examples: racket-show-pseudo-tooltip and racket-show-pos-tip.
A function that shows STR in a fixed location may of course ignore POS. Examples: racket-show-echo-area and racket-show-header-line
How racket-racket and racket-raco-test run commands.
The function should accept a command string, not including a newline, get or create a suitable buffer, send the command, and send a newline or enter.
Predefined choices include racket-shell, racket-term, racket-ansi-term, and racket-vterm.
(racket-show-pseudo-tooltip str &optional pos)
Show using an overlay that resembles a tooltip.
This is nicer than racket-show-pos-tip because it:
x-gtk-use-system-tooltips
is nil.
On the other hand, this does not look as nice when displaying text that spans multiple lines or is too wide to fit the window. In that case, we simply left-justify everything and do not draw any border.
(racket-show-echo-area str &optional _pos)
Show things in the echo area.
A value for the variable racket-show-functions.
This does not add STR to the “Messages” log buffer.
(racket-show-header-line str &optional _pos)
Show things using a buffer header line.
A value for the variable racket-show-functions.
When there is nothing to show, keep a blank header-line. That way, the buffer below doesn’t “jump up and down” by a line as messages appear and disappear. Only when V is nil do we remove the header line.
(racket-show-pos-tip str &optional pos)
Show things using pos-tip-show
if available.
A value for the variable racket-show-functions.
(racket-repl-buffer-name-unique)
Each racket-mode edit buffer gets its own racket-repl-mode buffer.
A value for the variable racket-repl-buffer-name-function.
(racket-repl-buffer-name-project)
Share a racket-repl-mode buffer per back end and per project.
A value for the variable racket-repl-buffer-name-function.
The “project” is determined by racket-project-root.
(racket-project-root file)
Given an absolute pathname for FILE, return its project root directory.
The “project” is determined by trying, in order:
projectile-project-root
vc-root-dir
project-current
file-name-directory
(racket-browse-url-using-temporary-file url &rest _args)
Browse a URL via a temporary HTML file using a meta redirect.
A suitable value for the variable racket-browse-url-function.
Racket documentation URLs depend on anchors – the portion of the URL after the # character – to jump to a location within a page. Unfortunately on some operating systems and/or versions of Emacs, the default handling for browsing file URLs ignores anchors. This function attempts to avoid the problem by using a temporary HTML file with a meta redirect as a “trampoline”.
Although the intent is to provide a default that “just works”,
you do not need to use this. You can customize the variable
racket-browse-url-function instead to be browse-url
, or
browse-url-browser-function
in case have have customized that,
or indeed whatever you want.
(racket-add-back-end directory &rest plist)
Add a description of a Racket Mode back end.
Racket Mode supports one or more back ends, which are Racket processes supporting REPLs as well as various other Racket Mode features.
DIRECTORY is a string describing a file-name-absolute-p
directory on some local or remote server.
When a back end’s DIRECTORY is the longest matching prefix of a
buffer’s default-directory
, that back end is used for the
buffer.
DIRECTORY can be a local directory like “/” or
“/path/to/project”, or a file-remote-p
directory like
“/user@host:” or “/user@host:/path/to/project”.
Note that you need not include a method – such as the “ssh” in “/ssh:user@host:” – and if you do it is stripped: A back end process is always started using SSH. Even if multiple buffers for the same user+host+port use different methods, they will share the same back end.
Practically speaking, DIRECTORY is a path you could give to
find-file
to successfully find some local or remote file, but
omitting any method. (Some remote file shorthand forms get
expanded to at least “/method:host:”. When in doubt check
buffer-file-name
and follow its example.)
In addition to being used as a pattern to pick a back end for a buffer, DIRECTORY determines:
After DIRECTORY, the remainining arguments are optional; they are alternating :keywords and values describing some other properties of a back end:
When not nil this is used instead of the value of the customization variable racket-program.
Where on a remote host to copy the back end’s *.rkt files when
they do not exist or do not match the digest of the local
files. This must be file-name-absolute-p
on the remote. Only
supply the localname there (not a full file-remote-p
). The
default value is “/tmp/racket-mode-back-end”.
Whether the back end uses Windows style path names. Used to translate betwen slashes and backslashes between the Emacs front end (which uses slashes even on Windows) and the Racket back end (which expects native backslashes on Windows).
A list of directory-name-p
strings. Each directory, and
recursively its subdirectories, will be watched for file system
changes. After any changes are detected, the next
racket-run (or racket-run-module-at-point etc.) command
will ask you if it should restart the back end for you. This
may be helpful when you are changing source files used by the
back end.
The default property values are appropriate for whether DIRECTORY is local or remote:
system-type
.
Although the default values usually “just work” for local and remote back ends, you might want a special configuration. Here are a few examples.
;; 1. A back end configuration for "/" is ;; created automatically and works fine as a default ;; for buffers visiting local files, so we don't need ;; to add one here. ;; 2. However assume we want buffers under /var/tmp/8.0 ;; instead to use Racket 8.0. (racket-add-back-end "/var/tmp/8.0" :racket-program "~/racket/8.0/bin/racket") ;; 3. A back end configuration will be created ;; automatically for buffers visiting file names like ;; "/ssh:user@linode", so we don't need to add one here. ;; ;; If ~/.ssh/config defines a Host alias named "linode", ;; with HostName and User settings, a file name as simple as ;; "/linode:" would work fine with tramp -- and the ;; automatically created back end configuration would work ;; fine, too. ;; 4. For example's sake, assume for buffers visiting ;; /ssh:headless:~/gui-project/ we want :racket-program instead ;; to be "xvfb-run racket". (racket-add-back-end "/ssh:headless:~/gui-project/" :racket-program "xvfb-run racket")
If you use various versions of Racket by setting PATH values via
direnv, .envrc files and envrc-global-mode
, then you need a
distinct back end for each such project subdirectory. One
approach is to use racket-add-back-end for each project in your
Emacs init file. Another way to is to have a .dir-locals.el file
alongside each .envrc file:
((nil . ((eval . (racket-add-back-end default-directory)))))
(racket-shell cmd)
Run CMD using shell
.
A value for the variable racket-shell-or-terminal-function.
(racket-term cmd)
Run CMD using term
.
A value for the variable racket-shell-or-terminal-function.
(racket-ansi-term cmd)
Run CMD using ansi-term
.
A value for the variable racket-shell-or-terminal-function.
(racket-vterm cmd)
Run CMD using vterm
, if that package is installed.
A value for the variable racket-shell-or-terminal-function.
Face for symbols quoted using ’ or ‘.
This face is given only to symbols directly quoted using the
reader shorthands ’ or ‘. All other directly quoted values,
including symbols quoted using “quote” or “quasiquote”, get
the face font-lock-constant-face
.
Face for symbols quoted using #’ or #‘.
This face is given only to symbols directly quoted using the
reader shorthands #’ or #‘. All other directly quoted
values, including symbols quoted using “syntax” or
“quasisyntax”, get the face font-lock-constant-face
.
Face racket-xp-mode uses to highlight expressions in a tail position.
Face racket-xp-mode gives to the module language name.
See the variable nil
.
Face racket-xp-mode gives uses of bindings imported from the module language.
See the variable nil
.
Face racket-xp-mode gives to imported module names.
See the variable nil
.
Face racket-xp-mode gives uses of imported bindings.
See the variable nil
.
Face racket-xp-mode gives to local definitions.
See the variable nil
.
Face racket-xp-mode gives to uses of local definitions.
See the variable nil
.
Face racket-describe-mode
uses for links within documentation.
Note: When some special face is already specified by the
documentation, then to avoid visual clutter this face is NOT also
added.
Face racket-describe-mode
uses for external links.
See the variable racket-browse-url-function.
Face racket-describe-mode
uses for Scribble @example or @interactions output.
Face racket-hash-lang-mode uses for text tokens.
Racket Mode’s Racket code is delivered as part of the Emacs package — not as a Racket package. Delivering both Emacs and Racket code in one Emacs package simplifies installation and updates. The main drawback is that the Racket code is not automatically compiled, as would normally be done by raco pkg install
. To address this: See racket-mode-start-faster.