Merge pull request #1215 from codeflash-ai/fix/strip-js-import-extensions

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

Author: misrasaurabh1

codeflash/languages/javascript/module_system.py

@@ -184,10 +184,18 @@ def _get_relative_import_path(target_path: Path, source_path: Path) -> str:
 
 
 def add_js_extension(module_path: str) -> str:
-    """Add .js extension to relative module paths for ESM compatibility."""
-    if module_path.startswith(("./", "../")):
-        if not module_path.endswith(".js") and not module_path.endswith(".mjs"):
-            return module_path + ".js"
+    """Process module path for ESM compatibility.
+
+    NOTE: This function intentionally does NOT add extensions because:
+    1. TypeScript projects resolve modules without explicit extensions
+    2. Adding .js to .ts imports causes "Cannot find module" errors
+    3. Modern bundlers (webpack, vite, etc.) handle extension resolution automatically
+
+    The function name is preserved for backward compatibility but the behavior
+    has been changed to NOT add extensions.
+    """
+    # Previously this function added .js extensions, but this caused module resolution
+    # errors in TypeScript projects. We now preserve paths without adding extensions.
     return module_path
 
 

codeflash/verification/verifier.py

@@ -75,7 +75,7 @@ def generate_tests(
             func_name = function_to_optimize.function_name
             qualified_name = function_to_optimize.qualified_name
 
-            # First validate and fix import styles
+            # Validate and fix import styles (default vs named exports)
             generated_test_source = validate_and_fix_import_style(generated_test_source, source_file, func_name)
 
             # Convert module system if needed (e.g., CommonJS -> ESM for ESM projects)

tests/test_languages/test_javascript_instrumentation.py

@@ -651,4 +651,4 @@ def test_this_method_call_exact_output(self):
 
         expected = "        return codeflash.capture('Class.fibonacci', '1', this.fibonacci.bind(this), n - 1);"
         assert transformed == expected, f"Expected:\n{expected}\nGot:\n{transformed}"
-        assert counter == 1
+        assert counter == 1