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Add regex support #265

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26 changes: 26 additions & 0 deletions grammar.js
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Original file line number Diff line number Diff line change
Expand Up @@ -464,6 +464,7 @@ module.exports = grammar({
$.extension_expression,
$.lazy_expression,
$._jsx_element,
$.regex,
),

parenthesized_expression: ($) =>
Expand Down Expand Up @@ -752,6 +753,7 @@ module.exports = grammar({
$.number,
$.true,
$.false,
$.regex,
),

variant_pattern: ($) =>
Expand Down Expand Up @@ -1185,6 +1187,30 @@ module.exports = grammar({

extension_identifier: ($) => /[a-zA-Z0-9_\.]+/,

regex: ($) =>
seq(
"/",
field("pattern", $.regex_pattern),
token.immediate(prec(1, "/")),
optional(field("flags", $.regex_flags)),
),

regex_pattern: (_) =>
token.immediate(
prec(
-1,
repeat1(
choice(
seq("[", repeat(choice(seq("\\", /./), /[^\]\n\\]/)), "]"),
seq("\\", /./),
/[^/\\\[\n]/,
),
),
),
),

regex_flags: (_) => token.immediate(/[a-z]+/),
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Copilot AI Feb 18, 2026

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The regex_flags pattern allows any sequence of lowercase letters (pattern: /[a-z]+/). While JavaScript/ReScript officially supports only specific flags (g, i, m, s, u, y, d), this lenient validation allows invalid flags like "xyz" to parse without error. Consider whether stricter validation would be beneficial, such as:

regex_flags: (_) => token.immediate(/[gimsuy]+/)

However, the current implementation may be intentionally permissive for forward compatibility with potential new flags. If this is the intended behavior, it's acceptable, but it's worth documenting this design decision.

Suggested change
regex_flags: (_) => token.immediate(/[a-z]+/),
// Only allow officially supported JS/ReScript regex flags: g, i, m, s, u, y, d
regex_flags: (_) => token.immediate(/[gimsuyd]+/),

Copilot uses AI. Check for mistakes.

number: ($) => {
// OCaml: https://github.com/tree-sitter/tree-sitter-ocaml/blob/f1106bf834703f1f2f795da1a3b5f8f40174ffcc/ocaml/grammar.js#L26
const hex_literal = seq(
Expand Down
2 changes: 2 additions & 0 deletions queries/highlights.scm
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Expand Up @@ -73,6 +73,8 @@
] @string


(regex) @string.special

(character) @character
(escape_sequence) @string.escape

Expand Down
5 changes: 4 additions & 1 deletion queries/injections.scm
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@@ -1,5 +1,9 @@
((comment) @injection.content (#set! injection.language "comment"))

; regex literal
(regex
(regex_pattern) @injection.content (#set! injection.language "regex"))

; %re
(extension_expression
(extension_identifier) @_name
Expand All @@ -26,4 +30,3 @@
(#eq? @_name "relay")
(expression_statement
(_ (_) @injection.content (#set! injection.language "graphql") )))

129 changes: 129 additions & 0 deletions src/grammar.json
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