Fix: Add TypeScript transformer to runtime Jest config

[mohammedahmed18]

Problem

When Jest base config is TypeScript (.ts file), all TypeScript tests fail with syntax errors. This affects 23 out of 45 logs (~51%) - a systematic high-severity bug blocking all TypeScript optimizations.

Error:

SyntaxError: Unexpected token, expected "," (37:45)
> 37 | export function addDatasourceFlags(datasource: Datasource) {
     |                                              ^

Root Cause

The _create_runtime_jest_config() function creates a standalone config when the base config is .ts (cannot be directly required by Node.js). This standalone config was missing the TypeScript transformer configuration entirely.

Bug location: codeflash/languages/javascript/test_runner.py:668-696

Flow:

1. Jest base config is jest.config.ts (TypeScript)
2. _create_runtime_jest_config() detects .ts extension (line 642)
3. Creates standalone config (lines 688-696) to avoid requiring .ts file
4. Standalone config only includes: roots, testMatch, moduleNameMapper
5. NO transform configuration → Jest cannot parse TypeScript → Syntax errors

Fix

Added TypeScript transformer detection to standalone config creation path:

• Call _detect_typescript_transformer() to find ts-jest/@swc/jest/babel
• Inject transform config into the standalone runtime Jest config
• Preserves existing behavior when transformer is not available

Files Changed

• codeflash/languages/javascript/test_runner.py (12 lines added at lines 688-699)
• tests/test_languages/test_typescript_runtime_config_transform.py (new file, 137 lines, 4 tests)

Testing

✅ 4 new regression tests:

• test_runtime_config_includes_typescript_transform_with_ts_jest
• test_runtime_config_includes_typescript_transform_with_swc
• test_runtime_config_includes_typescript_transform_with_babel_fallback
• test_runtime_config_no_transform_when_no_typescript_transformer

✅ All 34 existing test_javascript_test_runner.py tests pass
✅ No linting/type errors (uv run prek passes)

Impact

Severity: HIGH
Fixes: 23 out of 45 failing optimization runs (~51%)
Trace IDs: 1f944efe-bdab-4f1e-81cc-19189023c81a (and 22 others)

Unblocks all TypeScript optimizations for projects using .ts Jest configs.

Verification

Before fix (runtime config):

module.exports = {
  roots: ["/path/to/project", "/path/to/tests"],
  testMatch: ['**/*.test.ts', ...],
  // NO transform - TypeScript fails!
};

After fix (runtime config):

module.exports = {
  roots: ["/path/to/project", "/path/to/tests"],
  testMatch: ['**/*.test.ts', ...],
  transform: {
    '^.+\\.(ts|tsx)$': ['ts-jest', { isolatedModules: true }],
  }, // ← Now includes TypeScript transformer!
};