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Regular Expression Syntax Highlighting only recognising control characters if uppercase

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#1,063 4 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
38/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
typescript, vscode
Domain
devtools, tooling

Research direction

Start by locating the regular-expression syntax grammar and its highlighting tests in the repository, then reproduce the reported difference between \cJ and \cj. Done means both equivalent control-character escape forms receive the same highlighting; verify the result with the relevant grammar tests or VS Code syntax highlighting.

Written by the indexing model from the issue text.

Description

Type: Bug

As per https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Regular_expressions/Character_escape#c:

\cJ and \cj are equivalent

The syntax highlighter in VSCode only puts the uppercase form in blue, seemingly recognising \c as a separate escape and j as a normal character.

It would be good to show both forms in blue.

VS Code version: Code 1.106.3 (bf9252a2fb45be6893dd8870c0bf37e2e1766d61, 2025-11-25T22:28:18.024Z)
OS version: Darwin arm64 24.6.0
Modes:

System Info
Item Value
CPUs Apple M4 (10 x 2400)
GPU Status 2d_canvas: enabled
direct_rendering_display_compositor: disabled_off_ok
gpu_compositing: enabled
multiple_raster_threads: enabled_on
opengl: enabled_on
rasterization: enabled
raw_draw: disabled_off_ok
skia_graphite: enabled_on
trees_in_viz: disabled_off
video_decode: enabled
video_encode: enabled
webgl: enabled
webgl2: enabled
webgpu: enabled
webnn: disabled_off
Load (avg) 2, 3, 3
Memory (System) 24.00GB (0.13GB free)
Process Argv --crash-reporter-id 25a900f1-fd90-425a-8691-a245dd6d0743
Screen Reader no
VM 0%
Extensions (21)
Extension Author (truncated) Version
markdown-mermaid bie 1.29.0
vscode-eslint dba 3.0.16
docker doc 0.18.0
githistory don 0.6.20
gitlens eam 17.7.1
prettier-vscode esb 11.0.2
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vscode-containers ms- 2.3.0
vscode-docker ms- 2.0.0
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debugpy ms- 2025.16.0
python ms- 2025.18.0
vscode-pylance ms- 2025.10.4
vscode-python-envs ms- 1.12.0
remote-explorer ms- 0.5.0
remote-server ms- 1.5.3
vscode-jest Ort 6.4.4
code-spell-checker str 4.3.2
svelte-vscode sve 109.12.0
explorer vit 1.36.0
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Dominant language
TypeScript
Stars
471
Forks
149
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