fix: strip file extensions from JS/TS import paths in generated tests

LLMs often add .js extensions to TypeScript import paths (e.g.,
`import { func } from '../module.js'`), but TypeScript/Jest module
resolution doesn't require explicit extensions. This causes
"Cannot find module" errors.

This change adds `strip_js_extensions()` function that removes
.js/.ts/.tsx/.jsx/.mjs/.mts extensions from relative import paths
in generated tests. The function handles:
- ES module imports: import { x } from '../path.js'
- CommonJS requires: require('../path.js')
- Jest mocks: jest.mock('../path.js'), jest.doMock(), etc.

External package imports (lodash, react, etc.) are preserved.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

django/aiservice/languages/js_ts/testgen.py

@@ -122,6 +122,43 @@ def _is_valid_js_identifier(name: str) -> bool:
     return bool(JS_IDENTIFIER_PATTERN.match(name)) and name not in reserved_words
 
 
+# Patterns to strip file extensions from import paths
+# LLMs sometimes add .js extensions to TypeScript imports, which breaks module resolution
+_JS_EXTENSION_PATTERN = re.compile(
+    r"""(from\s+['"])(\.{0,2}/[^'"]+?)(\.(?:js|ts|tsx|jsx|mjs|mts))(['"])"""
+)
+_REQUIRE_EXTENSION_PATTERN = re.compile(
+    r"""(require\s*\(\s*['"])(\.{0,2}/[^'"]+?)(\.(?:js|ts|tsx|jsx|mjs|mts))(['"]\s*\))"""
+)
+_JEST_MOCK_EXTENSION_PATTERN = re.compile(
+    r"""(jest\.(?:mock|doMock|unmock|requireActual|requireMock)\s*\(\s*['"])(\.{0,2}/[^'"]+?)(\.(?:js|ts|tsx|jsx|mjs|mts))(['"])"""
+)
+
+
+def strip_js_extensions(source: str) -> str:
+    """Strip .js/.ts/.tsx/.jsx extensions from relative import paths.
+
+    TypeScript and Jest's module resolution automatically resolve file extensions,
+    so adding them explicitly can cause "Cannot find module" errors when the LLM
+    adds incorrect extensions (e.g., .js to a .ts file).
+
+    This function removes extensions from:
+    - ES module imports: import { x } from '../path/file.js'
+    - CommonJS requires: require('../path/file.js')
+    - Jest mocks: jest.mock('../path/file.js')
+
+    Args:
+        source: The test source code.
+
+    Returns:
+        Source code with extensions stripped from relative import paths.
+
+    """
+    source = _JS_EXTENSION_PATTERN.sub(r"\1\2\4", source)
+    source = _REQUIRE_EXTENSION_PATTERN.sub(r"\1\2\4", source)
+    return _JEST_MOCK_EXTENSION_PATTERN.sub(r"\1\2\4", source)
+
+
 def _generate_import_statement(function_name: str, module_path: str) -> tuple[str, str]:
     """Generate appropriate import statement and accessor for JavaScript/TypeScript.
 
@@ -480,6 +517,9 @@ async def testgen_javascript(
             language=data.language,
         )
 
+        # Strip incorrect file extensions from import paths (LLMs sometimes add .js to .ts imports)
+        generated_test_source = strip_js_extensions(generated_test_source)
+
         ph(request.user, "aiservice-testgen-tests-generated", properties={"language": language})
 
         if hasattr(request, "should_log_features") and request.should_log_features:

django/aiservice/tests/testgen/test_testgen_javascript.py

@@ -285,3 +285,85 @@ class TestJavaScriptTestGenPromptContent:
         system_content = messages[0]["content"]
         # Should warn against mocking
         assert "mock" in system_content.lower() or "Mock" in system_content
+
+
+class TestStripJsExtensions:
+    """Tests for stripping file extensions from import paths.
+
+    These tests copy the regex patterns and function directly to avoid Django dependencies.
+    """
+
+    # Copy of patterns from aiservice/languages/js_ts/testgen.py
+    _JS_EXTENSION_PATTERN = re.compile(
+        r"""(from\s+['"])(\.{0,2}/[^'"]+?)(\.(?:js|ts|tsx|jsx|mjs|mts))(['"])"""
+    )
+    _REQUIRE_EXTENSION_PATTERN = re.compile(
+        r"""(require\s*\(\s*['"])(\.{0,2}/[^'"]+?)(\.(?:js|ts|tsx|jsx|mjs|mts))(['"]\s*\))"""
+    )
+    _JEST_MOCK_EXTENSION_PATTERN = re.compile(
+        r"""(jest\.(?:mock|doMock|unmock|requireActual|requireMock)\s*\(\s*['"])(\.{0,2}/[^'"]+?)(\.(?:js|ts|tsx|jsx|mjs|mts))(['"])"""
+    )
+
+    @staticmethod
+    def strip_js_extensions(source: str) -> str:
+        """Strip .js/.ts/.tsx/.jsx extensions from relative import paths."""
+        source = TestStripJsExtensions._JS_EXTENSION_PATTERN.sub(r"\1\2\4", source)
+        source = TestStripJsExtensions._REQUIRE_EXTENSION_PATTERN.sub(r"\1\2\4", source)
+        return TestStripJsExtensions._JEST_MOCK_EXTENSION_PATTERN.sub(r"\1\2\4", source)
+
+    def test_strip_js_extension_from_esm_import(self) -> None:
+        """Test stripping .js from ES module imports."""
+        code = "import { getDifferences } from '../src/utils/DynamicBindingUtils.js';"
+        expected = "import { getDifferences } from '../src/utils/DynamicBindingUtils';"
+
+        result = self.strip_js_extensions(code)
+        assert result == expected
+
+    def test_strip_ts_extension_from_esm_import(self) -> None:
+        """Test stripping .ts from ES module imports."""
+        code = "import { func } from './module.ts';"
+        expected = "import { func } from './module';"
+
+        result = self.strip_js_extensions(code)
+        assert result == expected
+
+    def test_strip_extension_from_require(self) -> None:
+        """Test stripping extensions from require() calls."""
+        code = "const { func } = require('../utils/helper.js');"
+        expected = "const { func } = require('../utils/helper');"
+
+        result = self.strip_js_extensions(code)
+        assert result == expected
+
+    def test_strip_extension_from_jest_mock(self) -> None:
+        """Test stripping extensions from jest.mock() calls."""
+        code = "jest.mock('../src/utils/DynamicBindingUtils.js');"
+        expected = "jest.mock('../src/utils/DynamicBindingUtils');"
+
+        result = self.strip_js_extensions(code)
+        assert result == expected
+
+    def test_preserve_external_package_imports(self) -> None:
+        """Test that external package imports are not modified."""
+        code = "import lodash from 'lodash';"
+
+        result = self.strip_js_extensions(code)
+        assert result == code  # Should be unchanged
+
+    def test_strip_multiple_extensions_in_file(self) -> None:
+        """Test stripping multiple extensions in a single file."""
+        code = """
+import { func1 } from '../utils/helper.js';
+import { func2 } from './local.ts';
+const { func3 } = require('../lib/util.tsx');
+jest.mock('../mocks/mock.jsx');
+"""
+        expected = """
+import { func1 } from '../utils/helper';
+import { func2 } from './local';
+const { func3 } = require('../lib/util');
+jest.mock('../mocks/mock');
+"""
+
+        result = self.strip_js_extensions(code)
+        assert result == expected