feat(coverage-istanbul): read coverage data without babel#752
Merged
9aoy merged 2 commits intoweb-infra-dev:mainfrom Dec 11, 2025
Merged
feat(coverage-istanbul): read coverage data without babel#7529aoy merged 2 commits intoweb-infra-dev:mainfrom
9aoy merged 2 commits intoweb-infra-dev:mainfrom
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Pull request overview
This PR refactors the coverage data extraction in @rstest/coverage-istanbul to use direct string parsing instead of babel/istanbul-lib-instrument, achieving a significant performance improvement (10.9x faster: 8.208s → 752ms for 761 files).
Key changes:
- Introduces a new string-based parser (
readInitialCoverage) that extracts coverage data by searching for a magic value and matching braces - Removes dependency on
istanbul-lib-instrumentand related babel packages - Simplifies the coverage data extraction logic in the provider
Reviewed changes
Copilot reviewed 4 out of 5 changed files in this pull request and generated 9 comments.
Show a summary per file
| File | Description |
|---|---|
| packages/coverage-istanbul/src/utils.ts | New file containing string-based coverage data parser to replace babel parsing |
| packages/coverage-istanbul/src/provider.ts | Simplified to use new local readInitialCoverage function instead of istanbul-lib-instrument |
| packages/coverage-istanbul/package.json | Removed istanbul-lib-instrument and @types/istanbul-lib-instrument dependencies |
| pnpm-lock.yaml | Updated lockfile reflecting removal of babel-related dependencies |
| packages/core/LICENSE.md | Updated magic-string repository URL format (unrelated to main PR purpose) |
Files not reviewed (1)
- pnpm-lock.yaml: Language not supported
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Comment on lines
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| let remainCloseBraceCount = 1; | ||
| while (remainCloseBraceCount > 0) { | ||
| closeBraceIndex++; | ||
| if (closeBraceIndex >= code.length) throw new Error(''); | ||
| const char = code[closeBraceIndex]; | ||
| if (char === '{') remainCloseBraceCount++; | ||
| else if (char === '}') remainCloseBraceCount--; |
There was a problem hiding this comment.
The variable name remainCloseBraceCount is slightly misleading since it tracks the number of braces that still need to be matched (starting from inside the object), not the number remaining to be processed. Consider renaming to braceDepth or closeBraceBalance to better reflect its purpose as a counter that tracks nesting depth.
Suggested change
| let remainCloseBraceCount = 1; | |
| while (remainCloseBraceCount > 0) { | |
| closeBraceIndex++; | |
| if (closeBraceIndex >= code.length) throw new Error(''); | |
| const char = code[closeBraceIndex]; | |
| if (char === '{') remainCloseBraceCount++; | |
| else if (char === '}') remainCloseBraceCount--; | |
| let braceDepth = 1; | |
| while (braceDepth > 0) { | |
| closeBraceIndex++; | |
| if (closeBraceIndex >= code.length) throw new Error(''); | |
| const char = code[closeBraceIndex]; | |
| if (char === '{') braceDepth++; | |
| else if (char === '}') braceDepth--; |
Comment on lines
+31
to
+47
| let remainOpenBraceCount = 1; | ||
| while (remainOpenBraceCount > 0) { | ||
| openBraceIndex--; | ||
| if (openBraceIndex < 0) throw new Error(''); | ||
| const char = code[openBraceIndex]; | ||
| if (char === '}') remainOpenBraceCount++; | ||
| else if (char === '{') remainOpenBraceCount--; | ||
| } | ||
|
|
||
| let closeBraceIndex = magicValueIndex; | ||
| let remainCloseBraceCount = 1; | ||
| while (remainCloseBraceCount > 0) { | ||
| closeBraceIndex++; | ||
| if (closeBraceIndex >= code.length) throw new Error(''); | ||
| const char = code[closeBraceIndex]; | ||
| if (char === '{') remainCloseBraceCount++; | ||
| else if (char === '}') remainCloseBraceCount--; |
There was a problem hiding this comment.
The variable name remainOpenBraceCount is slightly misleading since it tracks the number of braces that still need to be matched (starting from inside the object), not the number remaining to be processed. Consider renaming to braceDepth or openBraceBalance to better reflect its purpose as a counter that tracks nesting depth.
Suggested change
| let remainOpenBraceCount = 1; | |
| while (remainOpenBraceCount > 0) { | |
| openBraceIndex--; | |
| if (openBraceIndex < 0) throw new Error(''); | |
| const char = code[openBraceIndex]; | |
| if (char === '}') remainOpenBraceCount++; | |
| else if (char === '{') remainOpenBraceCount--; | |
| } | |
| let closeBraceIndex = magicValueIndex; | |
| let remainCloseBraceCount = 1; | |
| while (remainCloseBraceCount > 0) { | |
| closeBraceIndex++; | |
| if (closeBraceIndex >= code.length) throw new Error(''); | |
| const char = code[closeBraceIndex]; | |
| if (char === '{') remainCloseBraceCount++; | |
| else if (char === '}') remainCloseBraceCount--; | |
| let braceDepth = 1; | |
| while (braceDepth > 0) { | |
| openBraceIndex--; | |
| if (openBraceIndex < 0) throw new Error(''); | |
| const char = code[openBraceIndex]; | |
| if (char === '}') braceDepth++; | |
| else if (char === '{') braceDepth--; | |
| } | |
| let closeBraceIndex = magicValueIndex; | |
| let braceDepth2 = 1; | |
| while (braceDepth2 > 0) { | |
| closeBraceIndex++; | |
| if (closeBraceIndex >= code.length) throw new Error(''); | |
| const char = code[closeBraceIndex]; | |
| if (char === '{') braceDepth2++; | |
| else if (char === '}') braceDepth2--; |
9aoy
approved these changes
Dec 11, 2025
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Summary
Read coverage data from source code using string matching, babel is not required anymore.
Tested on a project containing 761 unused files,
generateCoverageForUntestedFilesmethod's total execution time was reduced from 8.208s to 752.164ms.Related Links
Checklist