chore(librarian): RaiseValue error if current and previous version match (googleapis#14381)

This PR addresses the feedback from
googleapis#14353 (comment)

Author: parthea

.generator/cli.py

@@ -846,6 +846,12 @@ def handle_release_init(
             the config.yaml.
         output(str): Path to the directory in the container where modified
             code should be placed.
+
+    Raises:
+        ValueError: if the version in `release-init-request.json` is
+            the same as the version in state.yaml
+        ValueError: if the `release-init-request.json` file in the given
+            librarian directory cannot be read.
     """
 
     try:
@@ -868,20 +874,26 @@ def handle_release_init(
             library_id = library_release_data["id"]
             library_changes = library_release_data["changes"]
             path_to_library = f"packages/{library_id}"
-            _update_version_for_library(repo, output, path_to_library, version)
 
             # Get previous version from state.yaml
             previous_version = _get_previous_version(library_id, librarian)
-            if previous_version != version:
-                _update_changelog_for_library(
-                    repo,
-                    output,
-                    library_changes,
-                    version,
-                    previous_version,
-                    library_id,
+            if previous_version == version:
+                raise ValueError(
+                    f"The version in {RELEASE_INIT_REQUEST_FILE} is the same as the version in {STATE_YAML_FILE}\n"
+                    f"{library_id} previous released version: {previous_version}\n"
+                    f"{library_id} current version: {version}\n"
                 )
 
+            _update_version_for_library(repo, output, path_to_library, version)
+            _update_changelog_for_library(
+                repo,
+                output,
+                library_changes,
+                version,
+                previous_version,
+                library_id,
+            )
+
     except Exception as e:
         raise ValueError(f"Release init failed: {e}") from e
 

.generator/test_cli.py

@@ -602,14 +602,51 @@ def test_handle_release_init_success(mocker, mock_release_init_request_file):
     handle_release_init()
 
 
-def test_handle_release_init_fail():
+def test_handle_release_init_fail_value_error_file():
     """
     Tests that handle_release_init fails to read `librarian/release-init-request.json`.
     """
-    with pytest.raises(ValueError):
+    with pytest.raises(ValueError, match="No such file or directory"):
         handle_release_init()
 
 
+def test_handle_release_init_fail_value_error_version(mocker):
+    m = mock_open()
+
+    mock_release_init_request_content = {
+        "libraries": [
+            {
+                "id": "google-cloud-another-library",
+                "apis": [{"path": "google/cloud/another/library/v1"}],
+                "release_triggered": False,
+                "version": "1.2.3",
+                "changes": [],
+            },
+            {
+                "id": "google-cloud-language",
+                "apis": [{"path": "google/cloud/language/v1"}],
+                "release_triggered": True,
+                "version": "1.2.2",
+                "changes": [],
+            },
+        ]
+    }
+    with unittest.mock.patch("cli.open", m):
+        mocker.patch(
+            "cli._get_libraries_to_prepare_for_release",
+            return_value=mock_release_init_request_content["libraries"],
+        )
+        mocker.patch("cli._get_previous_version", return_value="1.2.2")
+        mocker.patch("cli._process_changelog", return_value=None)
+        mocker.patch(
+            "cli._read_json_file", return_value=mock_release_init_request_content
+        )
+        with pytest.raises(
+            ValueError, match="is the same as the version in state.yaml"
+        ):
+            handle_release_init()
+
+
 def test_read_valid_text_file(mocker):
     """Tests reading a valid text file."""
     mock_content = "some text"