fix: escape all special characters in identifiers when stringifying

[spokodev]

Bug

charsToEscapeInName is missing several characters that are special in selector syntax, so stringify() produces selectors that re-parse to a different AST (or fail to parse). parse(stringify(x)) is no longer equal to x:

import { parse, stringify } from "css-what";

stringify(parse(String.raw`.x\&y`));         // ".x&y"        -> parses as 2 selectors (`&` nesting)
stringify(parse(String.raw`[data-foo\=bar]`)); // "[data-foo=bar]" -> name `data-foo` + operator `=`
stringify(parse(String.raw`.a\{b\}c`));      // ".a{b}c"      -> unparseable

This breaks round-tripping of modern class names that contain these characters — e.g. Tailwind arbitrary values and CSS-nesting fragments (grid-cols-[&], data-[x=y], …).

Fix

Add =, &, ?, @, `, { and } to charsToEscapeInName, so every special ASCII character in an identifier is escaped — completing the set alongside the # > < / , ; etc. that are already handled. Escaping is transparent to parse, so existing round-trips are unaffected; only previously-corrupted ones are fixed.

Tests

Added cases to the "Stringify CSS spec compliance" block in stringify.spec.ts (a=b → a\=b, &, {}, ?, @). They fail on main (the characters are emitted unescaped) and pass with this change. Full suite: 860 passing, no regressions.

Same class as #1056 (which added %); distinct from #1791, which fixes escape consumption on the parse side — this is escape production on the stringify side.

Summary by CodeRabbit

• Bug Fixes

  • Improved CSS selector escaping so tag/identifier names containing =, &, ?, @, backticks, {, and } are handled correctly.

• Tests

  • Expanded escape expectation coverage for these special-character identifiers.
  • Added round-trip verification to ensure selectors with escaped special characters consistently parse and stringify back to the original form.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: f75892da-7a13-4bdb-9b69-ef2826974498

📥 Commits

Reviewing files that changed from the base of the PR and between af3afa9 and c24aff0.

📒 Files selected for processing (1)

• src/stringify.spec.ts

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📝 Walkthrough

Walkthrough

charsToEscapeInName in stringify.ts is extended with seven additional special characters (=, &, ?, @, `, {, }), causing escapeName to hex/char-escape them during selector stringification. Corresponding test cases are added to the escapeCases table, and a new round-trip test suite validates that parsed selectors remain stable through stringify/parse cycles.

Changes

Escape character expansion

Layer / File(s)	Summary
Expand escape character set and test outputs src/stringify.ts, src/stringify.spec.ts	Adds =, &, ?, @, `, {, } to the escape character set in escapeName, and extends the escapeCases test table with five new entries asserting the correct escaped CSS output for those characters in a tag name.
Round-trip validation tests src/stringify.spec.ts	Adds a new test suite that validates stringify + parse round-tripping for selectors containing the newly escaped special characters, ensuring that parse(stringify(parse(selector))) equals parse(selector).

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐇 Hop hop, the curly brace must flee,
The @ and ? can no longer roam free,
A backtick, ampersand, equals sign too—
All hex-escaped now, tidy and true.
The rabbit has tidied the CSS zoo! 🌿

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately captures the main change: extending the escape character set in identifiers when stringifying. This directly reflects the core modification in both stringify.ts and the corresponding test coverage.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/stringify.spec.ts`:
- Around line 31-35: The test data array starting at line 31 is missing coverage
for the backtick character and specific round-trip selector contexts. Add test
cases to this array for the backtick escape (backtick paired with its escaped
equivalent string), and add three additional test cases for the exact round-trip
selector contexts mentioned in the PR: the class selector with escaped ampersand
(`.x\&y`), the data attribute selector with escaped equals (` [data-foo\=bar]`),
and the class selector with escaped braces (`.a\{b\}c`). Each test case should
follow the existing pattern of providing the input string, the expected escaped
output using String.raw, and a descriptive label.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 902c7b00-7785-47ad-87c4-7401897ac6e0

📥 Commits

Reviewing files that changed from the base of the PR and between 2d552b9 and af3afa9.

📒 Files selected for processing (2)

• src/stringify.spec.ts
• src/stringify.ts