fix(local): warn when CodeUri path does not exist before mounting

samcli/local/lambdafn/runtime.py

@@ -426,8 +426,7 @@ def _get_code_dir(self, code_path: str) -> str:
         This method handles a few different cases for ``code_path``:
             - ``code_path``is a existent zip/jar file: Unzip in a temp directory and return the temp directory
             - ``code_path`` is a existent directory: Return this immediately
-            - ``code_path`` is a file/dir that does not exist: Return it as is. May be this method is not clever to
-                detect the existence of the path
+            - ``code_path`` is a file/dir that does not exist: Log a warning and return it as is
 
         Parameters
         ----------
@@ -441,6 +440,14 @@ def _get_code_dir(self, code_path: str) -> str:
             Directory containing Lambda function code. It can be mounted directly in container
         """
 
+        if code_path and not os.path.exists(code_path):
+            LOG.warning(
+                "Local code path '%s' does not exist. It will be mounted as an empty directory in the "
+                "container, which will likely cause the invocation to fail. Verify the CodeUri/ContentUri "
+                "of your function or layer, or run 'sam build' if the path is a build artifact.",
+                code_path,
+            )
+
         if code_path and os.path.isfile(code_path) and code_path.endswith(self.SUPPORTED_ARCHIVE_EXTENSIONS):
             decompressed_dir: str = _unzip_file(code_path, mount_symlinks=self._mount_symlinks)
             self._temp_uncompressed_paths_to_be_cleaned += [decompressed_dir]

tests/unit/local/lambdafn/test_runtime.py

@@ -851,6 +851,46 @@ def test_must_return_a_valid_file(self, unzip_file_mock, shutil_mock, os_mock):
         # Because we never unzipped anything, we should never delete
         shutil_mock.rmtree.assert_not_called()
 
+    @patch("samcli.local.lambdafn.runtime.LOG")
+    @patch("samcli.local.lambdafn.runtime.os")
+    @patch("samcli.local.lambdafn.runtime.shutil")
+    @patch("samcli.local.lambdafn.runtime._unzip_file")
+    def test_must_warn_when_code_path_does_not_exist(self, unzip_file_mock, shutil_mock, os_mock, log_mock):
+        """
+        Input is a path that does not exist on the local machine
+        """
+        code_path = "/nonexistent/path"
+
+        os_mock.path.exists.return_value = False
+        os_mock.path.isfile.return_value = False
+
+        result = self.runtime._get_code_dir(code_path)
+        # code path must still be returned as is
+        self.assertEqual(result, code_path)
+
+        unzip_file_mock.assert_not_called()
+        log_mock.warning.assert_called_once()
+        # The warning must include the offending path
+        self.assertIn(code_path, log_mock.warning.call_args[0])
+
+    @patch("samcli.local.lambdafn.runtime.LOG")
+    @patch("samcli.local.lambdafn.runtime.os")
+    @patch("samcli.local.lambdafn.runtime.shutil")
+    @patch("samcli.local.lambdafn.runtime._unzip_file")
+    def test_must_not_warn_when_code_path_exists(self, unzip_file_mock, shutil_mock, os_mock, log_mock):
+        """
+        Input is a directory that exists, no warning must be logged
+        """
+        code_path = "codedir"
+
+        os_mock.path.exists.return_value = True
+        os_mock.path.isfile.return_value = False
+
+        result = self.runtime._get_code_dir(code_path)
+        self.assertEqual(result, code_path)
+
+        log_mock.warning.assert_not_called()
+
 
 class TestLambdaRuntime_unarchived_layer(TestCase):
     def setUp(self):