fix: JS/TS module system and test framework detection#1289
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TypeScript files always use ESM syntax (import/export), so they should be detected as ESM even when package.json doesn't have "type": "module". Changes: - Check file extension first (.ts, .tsx, .mts = ESM) - Only use package.json "type" if explicitly set (no default) - Fall through to file content analysis when type not specified This fixes Jest test timeouts caused by module system mismatch.
When determining the module system for generated tests, pass the source file path so TypeScript files are correctly detected as ESM rather than falling through to the "Defaulting to CommonJS" default.
… jest The TestConfig.test_framework property was hardcoded to return "jest" for JavaScript projects. This fix uses the get_js_test_framework_or_default() function from the test_framework singleton, which properly returns the detected test framework from package.json (jest, vitest, or mocha).
misrasaurabh1
previously approved these changes
Feb 3, 2026
This optimization achieves a **10% runtime improvement** by eliminating redundant string scanning operations.
## Key Optimization
**Combined duplicate passes over test_globals**: The original code performed two separate passes checking if test globals appear in the code:
1. First pass: `needs_import = any(...)` to determine if *any* global is present
2. Second pass: `used_globals = [g for g in test_globals if ...]` to collect *which* globals are present
The optimized version merges these into a single pass that directly builds the `used_globals` list, eliminating the `needs_import` variable entirely. This cuts the number of substring searches (e.g., `f"{g}(" in code`) roughly in half.
## Why This Speeds Up Execution
In Python, string containment checks using the `in` operator are O(n×m) operations where n is the length of the haystack and m is the length of the needle. With 9 test globals and potentially large code strings, scanning twice through the code for each global was a significant bottleneck. The line profiler confirms this:
- Original: Lines checking `needs_import` and `used_globals` consumed **19.8%** of runtime (8.6% + 11.2%)
- Optimized: Single `used_globals` check consumes **15.9%** of runtime
## Test Case Performance
The optimization shows particularly strong gains on test cases that:
- Use multiple test globals (16-43% faster on individual global tests)
- Have larger code strings with many test cases (up to 37% faster on `test_vitest_adds_expect_import`)
- Process files with complex nesting and mixed content (15-27% improvements)
Early-exit paths (non-vitest frameworks, existing imports, no globals needed) remain fast since they bypass the optimization entirely, showing minimal overhead changes (0-3%).
This is a clean, focused optimization that reduces algorithmic complexity without changing behavior or code structure, making it safe to merge.
Contributor
⚡️ Codeflash found optimizations for this PR📄 11% (0.11x) speedup for
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…2026-02-03T11.36.53 ⚡️ Speed up function `ensure_vitest_imports` by 11% in PR #1289 (`fix/js-module-detection`)
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Summary
Test plan