chore: verify library distribution name (#14441)

Fixes googleapis/librarian#1946 🦕

Author: ohmayr

.generator/Dockerfile

@@ -172,6 +172,10 @@ RUN git clone --depth 1 https://github.com/googleapis/synthtool.git /tmp/synthto
 bazel_env/bin/python3.9 -m pip install /tmp/synthtool nox && \
 rm -rf /tmp/synthtool
 
+# Install build which is used to get the metadata of package config files.
+COPY .generator/requirements.in .
+RUN python3.9 -m pip install -r requirements.in
+
 # Copy the CLI script into the container.
 COPY .generator/cli.py .
 RUN chmod a+rx ./cli.py

.generator/cli.py

@@ -27,6 +27,8 @@
 from pathlib import Path
 from typing import Dict, List
 
+import build.util
+
 try:
     import synthtool
     from synthtool.languages import python_mono_repo
@@ -546,12 +548,54 @@ def _verify_library_namespace(library_id: str, repo: str):
             )
 
 
+def _get_library_dist_name(library_id: str, repo: str) -> str:
+    """
+    Gets the package name by programmatically building the metadata.
+
+    Args:
+        library_id: id of the library.
+        repo: This directory will contain all directories that make up a
+            library, the .librarian folder, and any global file declared in
+            the config.yaml.
+
+    Returns:
+        str: The library name string if found, otherwise None.
+    """
+    library_path = f"{repo}/packages/{library_id}"
+    metadata = build.util.project_wheel_metadata(library_path)
+    return metadata.get("name")
+
+
+def _verify_library_dist_name(library_id: str, repo: str):
+    """Verifies the library distribution name against its config files.
+
+    This function ensures that:
+    1. At least one of `setup.py` or `pyproject.toml` exists and is valid.
+    2. Any existing config file's 'name' property matches the `library_id`.
+
+    Args:
+        library_id: id of the library.
+        repo: This directory will contain all directories that make up a
+            library, the .librarian folder, and any global file declared in
+            the config.yaml.
+
+    Raises:
+        ValueError: If a name in an existing config file does not match the `library_id`.
+    """
+    dist_name = _get_library_dist_name(library_id, repo)
+    if dist_name != library_id:
+        raise ValueError(
+            f"The distribution name `{dist_name}` does not match the folder `{library_id}`."
+        )
+
+
 def handle_build(librarian: str = LIBRARIAN_DIR, repo: str = REPO_DIR):
     """The main coordinator for validating client library generation."""
     try:
         request_data = _read_json_file(f"{librarian}/{BUILD_REQUEST_FILE}")
         library_id = _get_library_id(request_data)
         _verify_library_namespace(library_id, repo)
+        _verify_library_dist_name(library_id, repo)
         _run_nox_sessions(library_id, repo)
     except Exception as e:
         raise ValueError("Build failed.") from e

.generator/requirements-test.in

@@ -17,3 +17,4 @@ pytest-cov
 pytest-mock
 gcp-synthtool @ git+https://github.com/googleapis/synthtool@5aa438a342707842d11fbbb302c6277fbf9e4655
 starlark-pyo3>=2025.1
+build

.generator/requirements.in

@@ -0,0 +1 @@
+build

.generator/test_cli.py

@@ -37,6 +37,7 @@
     _copy_files_needed_for_post_processing,
     _create_main_version_header,
     _determine_bazel_rule,
+    _get_library_dist_name,
     _determine_library_namespace,
     _get_library_id,
     _get_libraries_to_prepare_for_release,
@@ -52,6 +53,7 @@
     _update_changelog_for_library,
     _update_global_changelog,
     _update_version_for_library,
+    _verify_library_dist_name,
     _verify_library_namespace,
     _write_json_file,
     _write_text_file,
@@ -525,7 +527,8 @@ def test_handle_build_success(caplog, mocker, mock_build_request_file):
     caplog.set_level(logging.INFO)
 
     mocker.patch("cli._run_nox_sessions")
-    mocker.patch("cli._verify_library_namespace", return_value=True)
+    mocker.patch("cli._verify_library_namespace")
+    mocker.patch("cli._verify_library_dist_name")
     handle_build()
 
     assert "'build' command executed." in caplog.text
@@ -922,6 +925,26 @@ def test_determine_library_namespace_fails_not_subpath():
         _determine_library_namespace(gapic_parent_path, pkg_root_path)
 
 
+def test_get_library_dist_name_success(mocker):
+    mock_metadata = {"name": "my-lib", "version": "1.0.0"}
+    mocker.patch("build.util.project_wheel_metadata", return_value=mock_metadata)
+    assert _get_library_dist_name("my-lib", "repo") == "my-lib"
+
+
+def test_verify_library_dist_name_setup_success(mocker):
+    """Tests success when a library distribution name in setup.py is valid."""
+    mock_setup_file = mocker.patch("cli._get_library_dist_name", return_value="my-lib")
+    _verify_library_dist_name("my-lib", "repo")
+    mock_setup_file.assert_called_once_with("my-lib", "repo")
+
+
+def test_verify_library_dist_name_fail(mocker):
+    """Tests failure when a library-id does not match the libary distribution name."""
+    mocker.patch("cli._get_library_dist_name", return_value="invalid-lib")
+    with pytest.raises(ValueError):
+        _verify_library_dist_name("my-lib", "repo")
+
+
 def test_verify_library_namespace_success_valid(mocker, mock_path_class):
     """Tests success when a single valid namespace is found."""
     # 1. Get the mock instance from the mock class's return_value