safegaurd existing workflow

Author: ohmayr

.generator/cli.py

@@ -307,13 +307,21 @@ def _copy_files_needed_for_post_processing(output: str, input: str, library_id:
     """
 
     path_to_library = f"packages/{library_id}"
+    repo_metadata_path = f"{input}/{path_to_library}/.repo-metadata.json"
 
     # We need to create these directories so that we can copy files necessary for post-processing.
-    os.makedirs(f"{output}/{path_to_library}/scripts/client-post-processing", exist_ok=True)
-    shutil.copy(
-        f"{input}/{path_to_library}/.repo-metadata.json",
-        f"{output}/{path_to_library}/.repo-metadata.json",
+    os.makedirs(
+        f"{output}/{path_to_library}/scripts/client-post-processing", exist_ok=True
     )
+    # TODO(ohmayr): if `.repo-metadata.json` for a library exists in
+    # ``.librarian/generator-input`, then we override the generated `.repo-metadata.json`
+    # with what we have in `generator-input`. Remove this logic once the
+    # generated `.repo-metadata.json` file is completely backfilled.
+    if os.path.exists(repo_metadata_path):
+        shutil.copy(
+            repo_metadata_path,
+            f"{output}/{path_to_library}/.repo-metadata.json",
+        )
 
     # copy post-procesing files
     for post_processing_file in glob.glob(

.generator/test_cli.py

@@ -724,13 +724,28 @@ def test_invalid_json(mocker):
         _read_json_file("fake/path.json")
 
 
-def test_copy_files_needed_for_post_processing_success(mocker):
+def test_copy_files_needed_for_post_processing_copies_metadata_if_exists(mocker):
+    """Tests that .repo-metadata.json is copied if it exists."""
     mock_makedirs = mocker.patch("os.makedirs")
     mock_shutil_copy = mocker.patch("shutil.copy")
+    mocker.patch("os.path.exists", return_value=True)
+
     _copy_files_needed_for_post_processing("output", "input", "library_id")
 
-    mock_makedirs.assert_called()
     mock_shutil_copy.assert_called_once()
+    mock_makedirs.assert_called()
+
+
+def test_copy_files_needed_for_post_processing_skips_metadata_if_not_exists(mocker):
+    """Tests that .repo-metadata.json is not copied if it does not exist."""
+    mock_makedirs = mocker.patch("os.makedirs")
+    mock_shutil_copy = mocker.patch("shutil.copy")
+    mocker.patch("os.path.exists", return_value=False)
+
+    _copy_files_needed_for_post_processing("output", "input", "library_id")
+
+    mock_shutil_copy.assert_not_called()
+    mock_makedirs.assert_called()
 
 
 def test_clean_up_files_after_post_processing_success(mocker):