Racket Mode

Table of Contents

Racket Mode


Introduction

The Racket Mode package consists of a variety of Emacs major and minor modes, including:

For code, issues, and pull requests, see the Git repo.

To fund this work, see GitHub Sponsors or PayPal.


Install

The recommended way to use Racket Mode is to install the package from MELPA.


Configure Emacs to use MELPA

To use MELPA:

(require 'package)
(add-to-list 'package-archives
              '("melpa" . "https://melpa.org/packages/")
              t)

Install Racket Mode

When Emacs is configured to use MELPA, simply type M-x package-install RET racket-mode RET .


Minimal Racket

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 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.


Uninstall

To uninstall Racket Mode, simply type M-x package-delete RET racket-mode RET .

You should probably also exit and restart Emacs.


Update


Upgrading all packages

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:

  1. Use M-x list-packages. It should display a message like “42 packages can be upgraded; type ‘U’ to mark them for upgrading.”.
  2. Press U as suggested to mark them all.
  3. Press x to execute.

After such a mass update, it might be wise to exist restart Emacs.


Updating just Racket Mode

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:

  1. Uninstall Racket Mode: M-x package-delete RET racket-mode RET .
  2. Optional but most reliable: Exit and restart Emacs.
  3. Install Racket Mode: M-x package-install RET racket-mode RET . This will install the latest version.

Configure

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.


Key bindings

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.


Font-lock (syntax highlighting)

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:


Completion at point

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.

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.


Completion in minibuffer

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.)


Xref (definitions and references)

Several modes support the Emacs commands

To do so, each mode adds a local hook for xref-backend-functions:

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:

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.


Indent

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.)


paredit

If you use paredit, you might want to add keybindings to paredit-mode-map:

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))))

smartparens

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)

Appearance of parentheses

If you prefer parentheses to appear “dimmed”, see paren-face.

If you prefer the opposite, see rainbow-delimiters.


Edit buffers and REPL buffers

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:

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)))

eldoc

By default Racket Mode sets eldoc-documentation-function to nil — no eldoc-mode support. You may set it to racket-eldoc-function in a racket-mode-hook and racket-repl-mode-hook if you really want to use eldoc-mode with Racket. But it is not a very satisfying experience because Racket is not a very “eldoc-friendly” language. Although Racket Mode attempts to discover argument lists, contracts, or types this doesn’t work in many common cases:

A more satisfying experience is to use racket-xp-describe or racket-xp-documentation.


Start faster

You can use racket-mode-start-faster to make the Racket REPL start faster.


Unicode input method

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.


Ligatures

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).


Architecture

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.

Emacs front end and one local back end. Command I/O via pipe (local) or ssh (remote). REPL I/O via one TCP connection per REPL buffer (local/remote). Each back end provides zero or more REPLs.

However you can configure using any number of back ends on any number of local or remote hosts.

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.)

Emacs front end and two local back ends — one for a project path. Command I/O via pipe (local) or ssh (remote). REPL I/O via one TCP connection per REPL buffer (local/remote). Each back end provides zero or more REPLs.

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.

Emacs front end and a back end on a remote host. Command I/O via pipe (local) or ssh (remote). REPL I/O via one TCP connection per REPL buffer (local/remote). Each back end provides zero or more REPLs.

Of course the remote can also use different back ends for different paths.

Emacs front end and two back ends on a remote host. Command I/O via pipe (local) or ssh (remote). REPL I/O via one TCP connection per REPL buffer (local/remote). Each back end provides zero or more REPLs.

And of course you can have multiple remotes.

Emacs front end and two back ends each on two remote hosts. Command I/O via pipe (local) or ssh (remote). REPL I/O via one TCP connection per REPL buffer (local/remote). Each back end provides zero or more REPLs.

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.


Reference

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:


Commands


Edit


racket-mode

M-x racket-mode

Major mode for editing Racket source files.

KeyBinding
}racket-insert-closing
]racket-insert-closing
)racket-insert-closing
TABindent-for-tab-command
C-x C-eracket-send-last-sexp
C-M-yracket-insert-lambda
C-M-uracket-backward-up-list
C-M-xracket-send-definition
C-c C-uracket-unfold-all-tests
C-c C-fracket-fold-all-tests
C-c C-.racket-describe-search
C-c C-sracket-describe-search
C-c C-dracket-documentation-search
C-c C-pracket-cycle-paren-shapes
C-c C-x C-fracket-open-require-path
C-c C-e rracket-expand-region
C-c C-e eracket-expand-last-sexp
C-c C-e xracket-expand-definition
C-c C-e fracket-expand-file
C-c C-rracket-send-region
C-c C-oracket-profile
C-c C-lracket-logger
C-c C-tracket-test
C-c C-zracket-repl
C-c C-kracket-run-module-at-point
C-c C-cracket-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 step during initialization.


racket-insert-lambda

C-M-y

Insert λ.

To insert Unicode symbols generally, see racket-unicode-input-method-enable.


racket-fold-all-tests

C-c C-f

Fold (hide) all test submodules.


racket-unfold-all-tests

C-c C-u

Unfold (show) all test submodules.


racket-tidy-requires

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.


racket-trim-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.


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”.


racket-add-require-for-identifier

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.


racket-indent-line

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)

racket-smart-open-bracket-mode

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:

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.


racket-insert-closing

] 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.


racket-cycle-paren-shapes

C-c C-p

Cycle the sexpr among () [] {}.


racket-backward-up-list

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.


racket-unicode-input-method-enable

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:

omegaω
x_1x₁
x^1
A𝔸
test–>>Etest–>>∃ (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.


racket-align

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.


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.


racket-complete-at-point

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.


Explore


racket-xp-mode

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, racket-xp-next-error and racket-xp-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-, , 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.

KeyBinding
M-.xref-find-definitions
C-c C-sracket-describe-search
C-c C-dracket-xp-documentation
C-c C-.racket-xp-describe
C-c # Pracket-xp-previous-error
C-c # Nracket-xp-next-error
C-c # gracket-xp-annotate
C-c # <racket-xp-tail-previous-sibling
C-c # >racket-xp-tail-next-sibling
C-c # vracket-xp-tail-down
C-c # ^racket-xp-tail-up
C-c # rracket-xp-rename
C-c # ?xref-find-references
C-c # .xref-find-definitions
C-c # pracket-xp-previous-use
C-c # nracket-xp-next-use
C-c # kracket-xp-previous-definition
C-c # jracket-xp-next-definition

racket-xp-describe

C-c C-.

Describe the identifier at point.

The command varies based on how many C-u command prefixes you supply.

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.


racket-xp-documentation

C-c C-d

View documentation in an external web browser.

The command varies based on how many C-u command prefixes you supply.


racket-xp-next-definition

C-c # j

Move point to the next definition.


racket-xp-previous-definition

C-c # k

Move point to the previous definition.


racket-xp-next-use

C-c # n

When point is on a use, go to the next, sibling use.


racket-xp-previous-use

C-c # p

When point is on a use, go to the previous, sibling use.


racket-xp-next-error

C-c # N

Go to the next error.


racket-xp-previous-error

C-c # P

Go to the previous error.


racket-xp-tail-up

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.


racket-xp-tail-down

C-c # v

Go “down” to the first tail position enclosed by the current expression.


racket-xp-tail-next-sibling

C-c # >

Go to the next tail position sharing the same enclosing expression.


racket-xp-tail-previous-sibling

C-c # <

Go to the previous tail position sharing the same enclosing expression.


racket-documentation-search

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.


racket-describe-search

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.


Run


racket-repl-mode

M-x racket-repl-mode

Major mode for Racket REPL.

You may use xref-find-definitions M-. and xref-pop-marker-stack M-, : 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.

KeyBinding
}racket-insert-closing
]racket-insert-closing
)racket-insert-closing
C-c C-\racket-repl-exit
C-c C-cracket-repl-break
C-c C-lracket-logger
C-c C-zracket-repl-switch-to-edit
C-c C-sracket-describe-search
C-c C-.racket-repl-describe
C-c C-dracket-repl-documentation
C-c C-e rracket-expand-region
C-c C-e eracket-expand-last-sexp
C-c C-e xracket-expand-definition
C-c C-e fracket-expand-file
C-wcomint-kill-region
C-acomint-bol
C-M-yracket-insert-lambda
C-M-qprog-indent-sexp
C-M-uracket-backward-up-list
TABindent-for-tab-command
C-jnewline-and-indent
RETracket-repl-submit

In addition to any hooks its parent mode comint-mode might have run, this mode runs the hook racket-repl-mode-hook, as the final step during initialization.


racket-run

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.

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.

In the racket-repl-mode buffer, output that describes a file and position is automatically “linkified”. Examples of such text include:

To visit these locations, move point there and press RET or mouse click. Or, use the standard next-error and previous-error commands.


racket-run-and-switch-to-repl

<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.


racket-run-module-at-point

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.


racket-repl

C-c C-z

Show a Racket REPL buffer in some window.

IMPORTANT

The main, intended use of Racket Mode’s REPL is that you find-file some specific .rkt file, then run it using racket-run or racket-run-module-at-point. The resulting REPL will correspond to those definitions and match your expectations.

If you really want to start a REPL for no file in particular, then you could use this racket-repl command. But the resulting REPL will have a minimal “#lang racket/base” namespace. You could enter "(require racket)" if you want the equivalent of “#lang racket”. You could also "(require racket/enter)" if you want things like “enter!”. But in some sense you’d be “using it wrong”. If you actually don’t want to use Racket Mode’s REPL as intended, then consider using a plain Emacs shell buffer to run command-line Racket.


racket-repl-describe

C-c C-.

Describe the identifier at point.

The command varies based on how many C-u prefix arguments you supply.

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.


racket-repl-documentation

C-c C-d

View documentation in an external web browser.

The command varies based on how many C-u command prefixes you supply.


racket-racket

<C-M-f5>

Do “racket <file>” in a shell buffer.


racket-profile

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.


racket-profile-mode

M-x racket-profile-mode

Major mode for results of racket-profile.

KeyBinding
RETracket-profile-visit
.racket-profile-visit
fracket-profile-show-non-project
zracket-profile-show-zero
gracket-profile-refresh
qquit-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 step during initialization.


racket-logger

C-c C-l

Create the racket-logger-mode buffer.


racket-logger-mode

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

KeyBinding
gracket-logger-clear
pracket-logger-previous-item
nracket-logger-next-item
wtoggle-truncate-lines
lracket-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 step during initialization.


racket-debug-mode

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:

  1. “Instrument” code for step debugging.

    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.

  2. When a break occurs, the racket-repl-mode prompt changes. In this debug REPL, local variables are available for you to use and even to 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:

KeyBinding
?racket-debug-help
hracket-debug-run-to-here
!racket-debug-toggle-breakpoint
Pracket-debug-prev-breakpoint
Nracket-debug-next-breakpoint
pracket-debug-prev-breakable
nracket-debug-next-breakable
gracket-debug-go
cracket-debug-continue
uracket-debug-step-out
oracket-debug-step-over
SPCracket-debug-step

racket-repl-clear

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.


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.


Test


racket-test

<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:


racket-raco-test

M-x racket-raco-test

Do “raco test -x <file>” in a shell buffer to run the “test” submodule.


Eval


racket-send-region

C-c C-r

Send the current region (if any) to the Racket REPL.


racket-send-definition

C-M-x

Send the current definition to the Racket REPL.


racket-send-last-sexp

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.


Collections


racket-open-require-path

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 “->”.


Macro expand


racket-stepper-mode

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.

KeyBinding
kracket-stepper-previous-item
pracket-stepper-previous-item
jracket-stepper-next-item
nracket-stepper-next-item
RETracket-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 step during initialization.


racket-expand-file

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 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 also expands syntax from racket/base – which can result in very many expansion steps.


racket-expand-region

C-c C-e r

Expand the active region using racket-stepper-mode.

Uses Racket’s expand-once in the namespace from the most recent racket-run.


racket-expand-definition

C-c C-e x

Expand the definition around point using racket-stepper-mode.

Uses Racket’s expand-once in the namespace from the most recent racket-run.


racket-expand-last-sexp

C-c C-e e

Expand the sexp before point using racket-stepper-mode.

Uses Racket’s expand-once in the namespace from the most recent racket-run.


Other


racket-debug-toggle-breakpoint

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.


racket-mode-start-faster

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.


racket-mode-start-slower

M-x racket-mode-start-slower

Delete the “compiled” directories made by racket-mode-start-faster.


Variables


General variables


racket-program

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.


racket-command-timeout

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.


racket-memory-limit

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).


racket-error-context

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.


racket-user-command-line-arguments

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")

racket-browse-url-function

Function to call to browse a URL.


racket-xp-after-change-refresh-delay

Seconds to wait before refreshing racket-xp-mode annotations.

Set to nil to disable automatic refresh and manually use racket-xp-annotate.


racket-xp-highlight-unused-regexp

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.


racket-documentation-search-location

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.


REPL variables


racket-repl-buffer-name-function

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.


racket-submodules-to-run

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:


racket-repl-history-directory

Directory for racket-repl-mode history files.


racket-history-filter-regexp

Input matching this regexp are NOT saved on the history list. Default value is a regexp to ignore input that is all whitespace.


racket-images-inline

Whether to display inline images in the REPL.


racket-imagemagick-props

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).


racket-images-keep-last

How many images to keep in the image cache.


racket-images-system-viewer

The image viewer program to use for racket-view-image.


racket-pretty-print

Use pretty-print instead of print in REPL?


Other variables


racket-indent-curly-as-sequence

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.


racket-indent-sequence-depth

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.


racket-pretty-lambda

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.


racket-smart-open-bracket-enable

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.


racket-logger-config

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.


racket-before-run-hook

Normal hook done before various Racket Mode run commands.

When hook functions are called, current-buffer is that of the racket-mode 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.


racket-after-run-hook

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 racket-mode 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.


racket-sexp-comment-fade

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.


Experimental debugger variables


racket-debuggable-files

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.


Showing information


racket-show-functions

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


Configuration functions


Showing information


racket-show-pseudo-tooltip

(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:

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

(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

(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

(racket-show-pos-tip str &optional pos)

Show things using pos-tip-show if available.

A value for the variable racket-show-functions.


Associating edit buffers with REPL buffers


racket-repl-buffer-name-shared

(racket-repl-buffer-name-shared)

All racket-mode edit buffers share one racket-repl-mode buffer per back end.

A value for the variable racket-repl-buffer-name-function.


racket-repl-buffer-name-unique

(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

(racket-repl-buffer-name-project)

All racket-mode buffers in a project share a racket-repl-mode buffer.

A value for the variable racket-repl-buffer-name-function.

The “project” is determined by racket-project-root.


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:


Browsing file URLs with anchors


racket-browse-url-using-temporary-file

(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.


Configuring back ends


racket-add-back-end

(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:

The default property values are appropriate for whether DIRECTORY is local or remote:

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")

Faces


All


racket-keyword-argument-face

Face for #:keyword arguments.


racket-reader-quoted-symbol-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 “quote” or “quasiquote”, get the face font-lock-constant-face.


racket-reader-syntax-quoted-symbol-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.


racket-here-string-face

Face for here strings.


racket-xp-def-face

Face racket-xp-mode uses to highlight definitions.


racket-xp-use-face

Face racket-xp-mode uses to highlight uses.


racket-xp-unused-face

Face racket-xp-mode uses to highlight unused requires or definitions.


racket-xp-tail-target-face

Face racket-xp-mode uses to highlight targets of a tail position.


racket-xp-tail-position-face

Face racket-xp-mode uses to highlight expressions in a tail position.


racket-logger-config-face

Face for racket-logger-mode configuration.


racket-logger-topic-face

Face for racket-logger-mode topics.


racket-logger-fatal-face

Face for racket-logger-mode fatal level.


racket-logger-error-face

Face for racket-logger-mode error level.


racket-logger-warning-face

Face for racket-logger-mode warning level.


racket-logger-info-face

Face for racket-logger-mode info level.


racket-logger-debug-face

Face for racket-logger-mode debug level.


racket-doc-link-face

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.


racket-ext-link-face

Face racket-describe-mode uses for external links. See the variable racket-browse-url-function.


racket-doc-output-face

Face racket-describe-mode uses for Scribble @example or @interactions output.


racket-doc-litchar-face

Face racket-describe-mode uses for Scribble @litchar.


Footnotes

(1)

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.