Re: Which face to use for highlighting interpolation delimiters?

[Dmitry Gutov <dgutov@yandex.ru>]

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On 06/01/2023 16:30, Eli Zaretskii wrote:
>> Date: Fri, 6 Jan 2023 15:50:02 +0200
>> Cc: emacs-devel<emacs-devel@gnu.org>
>> From: Dmitry Gutov<dgutov@yandex.ru>
>>
>>>> While we're at it, maybe a face for regexp literals as well?
>>> Sure.
>> Eli, could we still add that in emacs-29? We'll make it simply inherit
>> from string and use in a 2-3 ts modes for languages with regexp
>> literals. It's a pretty trivial change.
>>
>> If we defer it until Emacs 30, it will be kinda painful to use in
>> ELPA-distributed packages (e.g. python and hopefully ruby as well).
> In general OK, but please show the patch to add that, so I could know
> exactly what is being proposed.

Sure.

I think these 3 are the only languages we support that have regexp literals.

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diff --git a/etc/NEWS b/etc/NEWS
index 059278b08a1..5901b2718e9 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -798,6 +798,7 @@ filter/sentinel error has been handled.
 These faces are primarily meant for use with tree-sitter.  They are:
 'font-lock-bracket-face', 'font-lock-delimiter-face',
 'font-lock-escape-face', 'font-lock-number-face',
+'font-lock-regexp-face',
 'font-lock-misc-punctuation-face', 'font-lock-operator-face',
 'font-lock-property-face', and 'font-lock-punctuation-face'.
 
diff --git a/lisp/font-lock.el b/lisp/font-lock.el
index 74881a14ccf..99df8fb9e06 100644
--- a/lisp/font-lock.el
+++ b/lisp/font-lock.el
@@ -2073,6 +2073,12 @@ font-lock-preprocessor-face
   "Font Lock mode face used to highlight preprocessor directives."
   :group 'font-lock-faces)
 
+(defface font-lock-regexp-face
+  '((t :inherit font-lock-string-face))
+  "Font Lock mode face used to highlight regexp literals."
+  :group 'font-lock-faces
+  :version "29.1")
+
 (defface font-lock-regexp-grouping-backslash
   '((t :inherit bold))
   "Font Lock mode face for backslashes in Lisp regexp grouping constructs."
diff --git a/lisp/progmodes/js.el b/lisp/progmodes/js.el
index 90b9068fd5d..fe483f220da 100644
--- a/lisp/progmodes/js.el
+++ b/lisp/progmodes/js.el
@@ -3498,7 +3498,7 @@ js--treesit-font-lock-settings
 
    :language 'javascript
    :feature 'string
-   '((regex pattern: (regex_pattern)) @font-lock-string-face
+   '((regex pattern: (regex_pattern)) @font-lock-regexp-face
      (string) @font-lock-string-face)
 
    :language 'javascript
diff --git a/lisp/progmodes/ruby-ts-mode.el b/lisp/progmodes/ruby-ts-mode.el
index bf09726b34f..5f5de500435 100644
--- a/lisp/progmodes/ruby-ts-mode.el
+++ b/lisp/progmodes/ruby-ts-mode.el
@@ -227,10 +227,8 @@ ruby-ts--font-lock-settings
    ;; Also before 'operator because % and / are operators
    :language language
    :feature 'regexp
-   ;; TODO: We probably need a separate face for regexps everywhere.
-   ;; Maybe another one for regexp delimiters as well.
-   '((regex "/" @font-lock-string-face)
-     (regex _ (string_content) @font-lock-string-face))
+   '((regex "/" @font-lock-regexp-face)
+     (regex _ (string_content) @font-lock-regexp-face))
 
    :language language
    :feature 'operator
diff --git a/lisp/progmodes/typescript-ts-mode.el b/lisp/progmodes/typescript-ts-mode.el
index 4042e2b1013..5a9a7eea959 100644
--- a/lisp/progmodes/typescript-ts-mode.el
+++ b/lisp/progmodes/typescript-ts-mode.el
@@ -151,7 +151,7 @@ typescript-ts-mode--font-lock-settings
    :language language
    :override t
    :feature 'string
-   `((regex pattern: (regex_pattern)) @font-lock-string-face
+   `((regex pattern: (regex_pattern)) @font-lock-regexp-face
      (string) @font-lock-string-face
      (template_string) @js--fontify-template-string
      (template_substitution ["${" "}"] @font-lock-misc-punctuation-face))