chore(librarian): create changelog.md file for a new library generation (#14773)

This PR creates the `CHANGELOG.md` and `docs/CHANGELOG.md` for a new
package during the container configure command.

Author: ohmayr

.generator/cli.py

@@ -223,6 +223,23 @@ def _prepare_new_library_config(library_config: Dict) -> Dict:
     return library_config
 
 
+def _create_new_changelog_for_library(library_id: str, output: str):
+    """Creates a new changelog for the library.
+    Args:
+        library_id(str): The id of the library.
+        output(str): Path to the directory in the container where code
+            should be generated.
+    """
+    package_changelog_path = f"{output}/packages/{library_id}/CHANGELOG.md"
+    docs_changelog_path = f"{output}/packages/{library_id}/docs/CHANGELOG.md"
+
+    os.makedirs(os.path.dirname(package_changelog_path), exist_ok=True)
+    _write_text_file(package_changelog_path, "# Changelog\n")
+
+    os.makedirs(os.path.dirname(docs_changelog_path), exist_ok=True)
+    _write_text_file(docs_changelog_path, "# Changelog\n")
+
+
 def handle_configure(
     librarian: str = LIBRARIAN_DIR,
     source: str = SOURCE_DIR,
@@ -267,6 +284,10 @@ def handle_configure(
         )
         prepared_config = _prepare_new_library_config(new_library_config)
 
+        # Create a `CHANGELOG.md` and `docs/CHANGELOG.md` file for the new library
+        library_id = _get_library_id(prepared_config)
+        _create_new_changelog_for_library(library_id, output)
+
         # Write the new library configuration to configure-response.json.
         _write_json_file(f"{librarian}/configure-response.json", prepared_config)
 

.generator/test_cli.py

@@ -71,6 +71,7 @@
     _write_json_file,
     _write_text_file,
     _copy_readme_to_docs,
+    _create_new_changelog_for_library,
     handle_build,
     handle_configure,
     handle_generate,
@@ -293,6 +294,7 @@ def test_handle_configure_success(mock_configure_request_file, mocker):
     mock_prepare_config = mocker.patch(
         "cli._prepare_new_library_config", return_value={"id": "prepared"}
     )
+    mock_create_changelog = mocker.patch("cli._create_new_changelog_for_library")
 
     handle_configure()
 
@@ -310,6 +312,28 @@ def test_handle_configure_no_new_library(mocker):
     with pytest.raises(ValueError, match="Configuring a new library failed."):
         handle_configure()
 
+def test_create_new_changelog_for_library(mocker):
+    """Tests that the changelog files are created correctly."""
+    library_id = "google-cloud-language"
+    output = "output"
+    mock_makedirs = mocker.patch("os.makedirs")
+    mock_write_text_file = mocker.patch("cli._write_text_file")
+
+    _create_new_changelog_for_library(library_id, output)
+
+    package_changelog_path = f"{output}/packages/{library_id}/CHANGELOG.md"
+    docs_changelog_path = f"{output}/packages/{library_id}/docs/CHANGELOG.md"
+
+    # Check that makedirs was called for both parent directories
+    mock_makedirs.assert_any_call(os.path.dirname(package_changelog_path), exist_ok=True)
+    mock_makedirs.assert_any_call(os.path.dirname(docs_changelog_path), exist_ok=True)
+    assert mock_makedirs.call_count == 2
+
+    # Check that the files were "written" with the correct content
+    mock_write_text_file.assert_any_call(package_changelog_path, "# Changelog\n")
+    mock_write_text_file.assert_any_call(docs_changelog_path, "# Changelog\n")
+    assert mock_write_text_file.call_count == 2
+
 
 def test_get_new_library_config_found(mock_configure_request_data):
     """Tests that the new library configuration is returned when found."""