Add Swift highlighting

[Sheraff]

Changes

Swift fences currently fall back to plaintext. This adds an isolated swift definition (no aliases), registers it in the default entry, and exposes it as a selective import (@tanstack/highlight/languages/swift). It follows the same shape as the batch in #27: one module on the existing collectPatternRanges helpers with a small linear scanner for comments and strings, no new token classes, no new dependencies, no cross-language imports, and no changes to core or to existing language modules.

Context-aware behaviour: interpolated, multi-line, and raw #"…"# strings with nested quotes and parentheses inside \( ), nested block comments, #/…/# and bare /…/ regex literals vs division, argument labels, contextual keywords (open, package, set, some, … only in keyword position), attributes, and # directives and macros.

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).

Size tradeoff

Core + Swift, local Node 26: 7.30 KB minified / 3.41 KB gzip / 3.13 KB Brotli, with a 3.55 KB gzip budget. Core and every existing selective profile are unchanged. The all-language convenience entry grows from 49.99 KB minified / 16.82 KB gzip to 52.74 KB / 17.73 KB gzip, and its budget rises from 17.1 KB to 18.0 KB gzip.

Deliberate limits

• An interpolated string is a single string token; a comment inside \( ) is not recognised.
• Bare /…/ regexes are recognised only after =, (, ,, :, [, {, return, or case, and never span lines; elsewhere / is division. #/…/# has no such limit.
• Text( / Foo( are type (same choice as the Dart module); all-caps names like URL( stay plain; single-letter generics stay plain.
• Generic < / > are operators; ?. is ? plus a plain .; tuple access point.0 stays plain.
• Trailing closures are function only for .name { at line start or when the closure starts with $0, !$0, a capture list, or params in.
• Contextual modifiers are keywords only before a lowercase word, an uppercase name, (, or [; get / set only in accessor positions.
• Backticked names are never keywords; word boundaries are ASCII-only.

Notes

• Add Swift and PowerShell highlighting with rich language showcases #26 also adds Swift (together with PowerShell). This is an independent implementation written to the same conventions as Add Java, Kotlin, Rust, Ruby, C#, Dart, Lua, and Perl highlighting #27; it does not share code with Add Swift and PowerShell highlighting with rich language showcases #26.

Validation

• pnpm run verify passes locally on Node 26.4.0: typecheck, build, docs verification, skills validation, publint, package and packed-runtime checks, 216 tests in 20 files, 26 size profiles, and 21 benchmark profiles.
• test/swift.test.ts: 14 tests with a realistic showcase, focused regressions for every context-aware behaviour, negative cases for delimiters inside the wrong context, and plaintext fallback; every assertion also checks byte-for-byte source reconstruction.
• An independent review pass against realistic SwiftUI, async/Codable, library-README, and Package.swift samples; every issue found has a regression assertion.
• The tokenizer was timed on ~60k-character repeated-delimiter inputs (unterminated strings, raw strings, regexes, interpolation openers, nested comments) and stays under 20 ms per input.
• Dedicated benchmark profile: 159 ms median for 10,000 blocks (budget 1,200 ms).
• pnpm run changeset:status: one minor bump for @tanstack/highlight.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Added Swift syntax highlighting with support for strings, interpolation, regular expressions, nested comments, attributes, and other Swift syntax.
  • Added Swift as a supported language in the language list and individual language exports.
• Documentation
  • Updated language support and bundle-size information to include Swift and the expanded language set.

[changeset-bot]

🦋 Changeset detected

Latest commit: 0b8d429

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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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: defaults
• Review profile: CHILL
• Plan: Advanced
• Run ID: 27b8f457-4e75-4716-b463-35d666ebfa41

📥 Commits

Reviewing files that changed from the base of the PR and between 803baba and 0b8d429.

📒 Files selected for processing (18)

• .changeset/swift.md
• README.md
• docs/guides/performance.md
• docs/installation.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/index.ts
• src/languages/swift.ts
• test/fixtures.ts
• test/real-doc-fixtures.test.ts
• test/swift.test.ts

Included review availability: This review used your included allowance. Your plan provides up to 1 included review per hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

This change adds a Swift language definition to the highlighter, registers it in the language union, all-language registry, and exports, and adds Swift tests, benchmark coverage, bundle-size limits, and documentation.

Changes

Swift language support

Layer / File(s)	Summary
Swift tokenization and coverage src/languages/swift.ts, test/swift.test.ts, test/fixtures.ts, test/real-doc-fixtures.test.ts	The tokenizer identifies Swift syntax, including nested block comments, string interpolation, raw and multiline strings, and regex literals. Tests cover these forms and additional Swift syntax.
Language registration and catalog src/index.ts, src/languages/index.ts, scripts/language-utils.mjs, docs/language-support.md, docs/reference/*, skills/configure-selective-highlighting/references/languages.md, README.md, .changeset/swift.md	Swift is added to the language union, all-language registry, exports, and supported-language list. The language references and changeset include Swift.
Benchmark and bundle-size tracking scripts/bench.mjs, scripts/measure-size.mjs, README.md, docs/guides/performance.md, docs/installation.md, docs/test-strategy.md	A Swift benchmark and bundle-size profile are added. The all-language size figures and size budgets are updated.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~45 minutes

Change: Feature

Suggested reviewers: tannerlinsley

Merge Risk: ⚪ Minimal · up to 0b8d4

This adds Swift highlighting as an isolated, opt-in language module. Core and existing selective bundles are reported unchanged. No concrete merge-blocking risk was found.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: adding Swift highlighting.
Description check	✅ Passed	The description covers the required Changes and Validation sections. It explains the behavior, scope, deliberate limits, size impact, tests, and benchmark results.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 9 files. (9 skipped: 9 …
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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