Detect more browser hacks in values

[bartveneman]

Summary

Extends browser hack detection to identify Internet Explorer-specific CSS hacks used in property values, beyond the existing \9 hack detection. This provides more comprehensive analysis of legacy IE compatibility code.

Key Changes

• New isValueBrowserhack() function in src/values/browserhacks.ts that detects multiple IE hack patterns:

  • progid: prefix for DXImageTransform filters (case-insensitive)
  • Trailing \9 (IE9) and \7 (IE7) escape hacks on identifiers
  • alpha() function for IE opacity (case-insensitive)
  • expression() function for IE dynamic values (case-insensitive)
  • .htc behavior files in url() functions (case-insensitive)

• Updated detection logic in src/index.ts:

  • Replaced single isIe9Hack() check with comprehensive isValueBrowserhack() callback
  • Added guard to exclude custom properties (--*) from hack detection
  • Maintains existing text trimming for \9 and \7 hacks

• Comprehensive test coverage with 26 new test cases covering:

  • Detection of each hack type with various formats (quoted, unquoted, case variations)
  • Multiple hacks in single declaration
  • False positive prevention (regular URLs, gradients, custom properties, aspect-ratio values)

• Public API export of isValueBrowserhack() function for external use

Implementation Details

• Uses regex pattern matching for progid: detection to handle quoted and unquoted values
• Walks the CSS AST to identify function nodes (alpha(), expression()) and URL nodes (.htc files)
• Properly excludes custom properties from all hack detection patterns to avoid false positives
• Maintains backward compatibility with existing isIe9Hack() function

https://claude.ai/code/session_016WKR6cnpvkF5ApX7tt7KoC

[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.30769% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.48%. Comparing base (16ff190) to head (edb1cd8).

Files with missing lines	Patch %	Lines
src/index.ts	87.50%	1 Missing ⚠️
src/values/browserhacks.ts	94.44%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #584      +/-   ##
==========================================
- Coverage   95.20%   94.48%   -0.72%     
==========================================
  Files          18       18              
  Lines        1000     1016      +16     
  Branches      314      321       +7     
==========================================
+ Hits          952      960       +8     
- Misses         40       46       +6     
- Partials        8       10       +2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[codecov-commenter]

Bundle Report

Changes will increase total bundle size by 1.32kB (1.68%) ⬆️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
analyzeCss-esm	79.75kB	1.32kB (1.68%) ⬆️

Affected Assets, Files, and Routes:

view changes for bundle: analyzeCss-esm

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
index.js	6 bytes	33.1kB	0.02%
index.d.ts	45 bytes	14.63kB	0.31%
browserhacks-BZeV9_0h.js (New)	8.97kB	8.97kB	100.0% 🚀
values/index.d.ts	-41 bytes	1.49kB	-2.69%
values-DI2FP2Ey.d.ts (New)	1.31kB	1.31kB	100.0% 🚀
values/index.js	45 bytes	462 bytes	10.79% ⚠️
browserhacks-TJ8g2OK2.js (Deleted)	-8.19kB	0 bytes	-100.0% 🗑️
values-D6esXWUv.d.ts (Deleted)	-820 bytes	0 bytes	-100.0% 🗑️

Files in index.js:

• ./src/index.ts → Total Size: 26.46kB

Files in browserhacks-BZeV9_0h.js:

• ./src/values/browserhacks.ts → Total Size: 1.02kB

Files in values/index.js:

• ./src/values/index.ts → Total Size: 0 bytes