Add C highlighting by DreierF · Pull Request #36 · TanStack/highlight

DreierF · 2026-10-21T12:31:23Z

Changes

C fences currently fall back to plaintext. This adds an isolated c definition with an h alias, registers it in the default entry, and exposes it as a selective import (@tanstack/highlight/languages/c). It follows the shape of the C++ module: one module on the existing patternTokenizer, no new token classes, no new dependencies, no cross-language imports, and no changes to core or to existing language modules.

c is a separate definition rather than an alias of cpp because C code can use new, class, this, template, and namespace as ordinary identifiers, which the C++ definition highlights as keywords. C also has keywords that C++ lacks, such as restrict, _Generic, _Static_assert, and _Atomic.

Context-aware behaviour: prefixed strings and character literals, include and embed paths, preprocessor directives, line comments continued by a trailing backslash, C11 and C23 keywords and types, digit separators, and wb suffixes. C++-only words stay plain.

The branch is one commit for the module and tests, then one registration commit (default entry, barrel, size and bench profiles, fixture, docs tables, changeset).

Proposal: #34

Validation

pnpm run verify passes, including the new test/c.test.ts and a representative fixture in test/fixtures.ts.

Core + C, local Node 24: 6.04 KB minified / 2.84 KB gzip / 2.63 KB Brotli, with a 2.95 KB gzip budget. Core and every existing selective profile are unchanged. The all-language convenience entry grows from 52.74 KB minified / 17.68 KB gzip to 54.19 KB / 17.88 KB gzip, and its budget rises from 18.0 KB to 18.15 KB gzip.

#37 (ABAP) touches the same registration lines and size budget. Whichever merges second needs a small rebase.

🤖 Generated with Claude Code

Summary by CodeRabbit

New Features
- Added C syntax highlighting support.
- Added c as a supported language with h as an alias.
- Supports C comments, strings, character literals, preprocessor directives, C11/C23 keywords, types, numbers, functions, and operators.
Documentation
- Updated language lists, references, performance metrics, bundle sizes, and selective-highlighting guidance to include C support.
Tests
- Added coverage for C syntax highlighting, language distinctions, and alias handling.

C fences currently fall back to plaintext, and registering `c` as a `cpp` alias would mark valid C identifiers such as `new`, `class`, and `this` as keywords. This adds a standalone `c` definition with an `h` alias on the existing pattern tokenizer. It covers prefixed strings, character literals, include paths, preprocessor directives, C11 and C23 keywords and types, and C23 digit separators and `wb` suffixes. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Adds C to the default entry and language barrel, with a size and benchmark profile, a representative fixture, docs tables, and a minor changeset. The all-language convenience entry grows from 17.68 KB to 17.88 KB gzip and its budget rises to 18.15 KB; core and existing selective profiles are unchanged. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

changeset-bot · 2026-10-21T12:31:35Z

🦋 Changeset detected

Latest commit: e2c0df0

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@tanstack/highlight	Minor

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coderabbitai · 2026-10-21T12:31:38Z

No actionable comments were generated in the recent review. 🎉

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📥 Commits

Reviewing files that changed from the base of the PR and between 41a0ece and e2c0df0.

📒 Files selected for processing: 2

src/languages/c.ts
test/c.test.ts

🚧 Files skipped from review as they are similar to previous changes: 1

test/c.test.ts

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📝 Walkthrough

The package adds a C language tokenizer, registers and exports it, and maps the h alias to C. Tests cover C syntax and alias handling. Benchmarking, bundle-size limits, documentation, and the release entry are updated.

Changes: C language support

Layer / File(s)	Summary
C tokenizer and registration `src/languages/c.ts`, `src/index.ts`, `src/languages/index.ts`, `test/c.test.ts`, `test/fixtures.ts`, `test/real-doc-fixtures.test.ts`	Adds the C tokenizer and registers and exports it. Tests cover syntax, token reconstruction, fixtures, and alias behavior.
Language tooling and measurements `scripts/language-utils.mjs`, `scripts/bench.mjs`, `scripts/measure-size.mjs`	Adds C language and `h` alias recognition to tooling. Adds C benchmark and bundle-size profiles, and raises the all-language size limits.
Documentation and release entry `.changeset/c.md`, `README.md`, `docs/guides/performance.md`, `docs/language-support.md`, `docs/reference/*`, `docs/test-strategy.md`, `skills/configure-selective-highlighting/references/languages.md`	Documents C support, its export and alias, updated language counts, bundle measurements, benchmark coverage, and the minor release entry.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant Consumer
  participant HighlightLanguage
  participant allLanguages
  participant CTokenizer
  Consumer->>HighlightLanguage: Select `c` or `h`
  HighlightLanguage->>allLanguages: Resolve registered C language
  allLanguages->>CTokenizer: Tokenize C source
  CTokenizer-->>Consumer: Return highlighted tokens

Merge Risk: ⚪ Minimal · up to e2c0d

No actionable merge risk remains from the reviewed change.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 9 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description check		The description includes both required sections. It explains the C highlighting behavior, implementation scope, tests, verification command, bundle-size results, and benchmark budgets.
Title check		The title, "Add C highlighting," is concise, specific, and accurately summarizes the primary change.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

🔇 Additional comments: 12

scripts/language-utils.mjs: 1

6-6: LGTM!

Also applies to: 48-48

scripts/bench.mjs: 1

59-64: LGTM!

scripts/measure-size.mjs: 1

83-91: LGTM!

Also applies to: 197-197

.changeset/c.md: 1

1-5: LGTM!

README.md: 1

198-198: LGTM!

Also applies to: 221-221

docs/guides/performance.md: 1

11-19: LGTM!

Also applies to: 29-29

docs/language-support.md: 1

14-14: LGTM!

docs/reference/default-entry.md: 1

46-46: LGTM!

docs/reference/languages.md: 1

25-25: LGTM!

Also applies to: 65-65

docs/test-strategy.md: 1

22-30: LGTM!

skills/configure-selective-highlighting/references/languages.md: 1

8-8: LGTM!

docs/test-strategy.md-36-36: 1

36-36: 📐 Maintainability & Code Quality | 🟡 Minor | ⚡ Quick win

⚠️ Unverified finding
Verification ran but could not confirm this finding. It is shown for review, not as a verified issue.

Hyphenate the benchmark timing terms.

Change two warmup passes to two warm-up passes and 1.2 second CI budget to 1.2-second CI budget. This keeps the benchmark description grammatically clear.

Source: Linters/SAST tools

🪄 Fix comments: Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
Review comments at @src/languages/c.ts:
- Line 11: Update the string-literal alternative in the C tokenizer regex to
exclude unescaped carriage returns and newlines from its ordinary-character
branch, while preserving escaped characters and line continuations; leave the
character-literal alternative unchanged.

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📒 Files selected for processing: 17

.changeset/c.md
README.md
docs/guides/performance.md
docs/language-support.md
docs/reference/default-entry.md
docs/reference/languages.md
docs/test-strategy.md
scripts/bench.mjs
scripts/language-utils.mjs
scripts/measure-size.mjs
skills/configure-selective-highlighting/references/languages.md
src/index.ts
src/languages/c.ts
src/languages/index.ts
test/c.test.ts
test/fixtures.ts
test/real-doc-fixtures.test.ts

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C string literals cannot contain an unescaped line break, so an unclosed `"` no longer marks the following lines as a string. Escaped line continuations stay inside the string. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

DreierF and others added 2 commits October 19, 2026 17:04

DreierF mentioned this pull request Oct 21, 2026

Add ABAP highlighting #37

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coderabbitai Bot reviewed Oct 21, 2026

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Comment thread src/languages/c.ts Outdated

End unterminated C strings at the line end

e2c0df0

C string literals cannot contain an unescaped line break, so an unclosed `"` no longer marks the following lines as a string. Escaped line continuations stay inside the string. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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Add C highlighting - #36

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