Fix Jest runtime config failing to load TypeScript base configs

[mohammedahmed18]

Problem

When a project uses jest.config.ts (TypeScript config), the generated runtime config tries to require('./jest.config.ts'), which fails because Node.js CommonJS cannot parse TypeScript syntax without compilation.

Error message:

SyntaxError: Missing initializer in const declaration
    at compileSourceTextModule (node:internal/modules/esm/utils:346:16)
    at loadESMFromCJS (node:internal/modules/cjs/loader:1363:24)

Impact

• Affected logs: 18 out of 38 optimization runs (~47%)
• Severity: HIGH - Blocks all TypeScript projects using jest.config.ts
• Affected trace IDs:
  • 0fd176bf-5c7f-4f41-8396-77c46be86412
  • (and 17 others - see logs in /workspace/logs)

Root Cause

Line 386 in codeflash/languages/javascript/test_runner.py used base_config_path.name directly without checking the file extension. The generated runtime config is always a .js file (CommonJS), so it cannot use require() on .ts files.

Before:

if base_config_path:
    require_path = f"./{base_config_path.name}"  # Generates require('./jest.config.ts')

After:

if base_config_path and base_config_path.suffix != ".ts":
    require_path = f"./{base_config_path.name}"  # Only require non-TypeScript configs

Solution

Check if base_config_path is a TypeScript file (.ts). If so, create a standalone runtime config without trying to extend it via require(). Jest will still discover and use the original TypeScript config naturally through its own resolution mechanism.

Testing

✅ Added comprehensive test in test_jest_typescript_config_bug.py

• Creates realistic TypeScript Jest config with type annotations
• Verifies generated runtime config loads without syntax errors
• Confirms Node.js can successfully require the generated config

✅ All existing tests pass:

• 34 JavaScript test runner tests
• 2 new TypeScript config tests
• No linting/type errors from uv run prek

Verification

To reproduce the original issue and verify the fix:

cd /workspace/target
codeflash --file packages/backend-core/src/users/utils.ts \
  --function isCreatorSync \
  --rerun 0fd176bf-5c7f-4f41-8396-77c46be86412

Before fix: Tests fail with "SyntaxError: Missing initializer in const declaration"
After fix: Tests run successfully

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🤖 Generated with autonomous debug loop (iteration 1/20)

[claude]

Claude finished @mohammedahmed18's task in 2m 29s —— View job

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PR Review Summary

PR size: SMALL — 5 lines of production code changed (test_runner.py +5/-1), plus a new test file (155 lines).

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Prek Checks

uv run prek run --from-ref origin/main — passed with no issues.

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Code Review

The core fix is correct. Adding base_config_path.suffix != ".ts" prevents the require('./jest.config.ts') crash. The fallback to a standalone config is the right behavior given the constraints.

Issues found:

1. Testing convention violation — tempfile.TemporaryDirectory() must be replaced with tmp_path

Per .claude/rules/testing.md: "Use pytest's tmp_path fixture for temp directories — do not use tempfile.mkdtemp(), tempfile.TemporaryDirectory(), or NamedTemporaryFile."

Both test methods in test_jest_typescript_config_bug.py use tempfile.TemporaryDirectory(). Fix this →

2. Docstrings in test methods violate project conventions

Per CLAUDE.md: "Do not add docstrings to new or changed code unless the user explicitly asks for them." The test methods have multi-line docstrings. The class and module-level docstring are borderline; the per-method docstrings should be removed. Fix this →

3. Fix misses .mts extension

TypeScript ESM module config files use .mts. The check suffix != ".ts" would still fail on jest.config.mts. Low risk since .mts Jest configs are uncommon, but worth a follow-up. Suggest changing to:

if base_config_path and base_config_path.suffix not in {".ts", ".mts", ".cts"}:

4. Related bug in _create_codeflash_jest_config (out of scope, but worth noting)

test_runner.py:300-304 has the same pattern — require('{config_require_path}') where config_require_path can be a .ts file. This function is used for ESM compatibility wrappers. It isn't fixed here and will still fail for TypeScript config projects that also need ESM wrapping.

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Duplicate Detection

No duplicates detected.

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Last updated: 2026-04-04T05:14:00Z