[WIP] Fix fetch-lib error in charmcraft 3.4.3

charmcraft/application/commands/store.py

@@ -1535,10 +1535,9 @@ def run(self, parsed_args: argparse.Namespace) -> None:
                 ]
             )
         except errors.LibraryError:
-            raise errors.LibraryError(
-                message=f"Library {parsed_args.library} not found in Charmhub.",
-                logpath_report=False,
-            )
+            # Re-raise the original error which has better details than parsed_args.library
+            # (which could be None if no library was specified on the command line)
+            raise
 
         # check if something needs to be done
         analysis = []
@@ -1559,7 +1558,7 @@ def run(self, parsed_args: argparse.Namespace) -> None:
                     break
             else:
                 raise errors.LibraryError(
-                    message=f"Library {parsed_args.library} not found in Charmhub.",
+                    message=f"Library {lib_data.full_name} not found in Charmhub.",
                     logpath_report=False,
                 )
             emit.debug(f"Store tip: {tip}")

tests/unit/commands/test_fetch_lib_command.py

@@ -0,0 +1,135 @@
+# Copyright 2024 Canonical Ltd.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# For further info, check https://github.com/canonical/charmcraft
+"""Unit tests for FetchLibCommand - specifically testing error message handling."""
+
+import argparse
+import pathlib
+from unittest import mock
+
+import pytest
+
+from charmcraft import errors
+from charmcraft.application.commands.store import FetchLibCommand
+from charmcraft.application.main import APP_METADATA
+from charmcraft.utils.charmlibs import LibData
+
+
+def test_fetchlibcommand_library_not_found_error_message_with_no_args(
+    service_factory, monkeypatch
+):
+    """Test that error message shows actual library name when no library argument is provided.
+
+    This test reproduces the bug where running `charmcraft fetch-lib` without arguments
+    and getting a LibraryError from the store would show "Library None not found in Charmhub."
+    instead of the actual library name.
+    """
+    # Create a mock LibData for a library that exists locally
+    lib_data = LibData(
+        lib_id="6c3e6b6680d64e9c89e611d1a15f65be",
+        api=0,
+        patch=40,
+        content="# Library content",
+        content_hash="abcd1234",
+        full_name="charms.opensearch.v0.helper_charm",
+        path=pathlib.Path("lib/charms/opensearch/v0/helper_charm.py"),
+        lib_name="helper_charm",
+        charm_name="opensearch",
+    )
+
+    # Mock utils.get_libs_from_tree to return our test library
+    mock_get_libs = mock.Mock(return_value=[lib_data])
+    monkeypatch.setattr(
+        "charmcraft.application.commands.store.utils.get_libs_from_tree",
+        mock_get_libs,
+    )
+
+    # Mock the store service to raise LibraryError when getting metadata
+    # This simulates the store not finding the library
+    mock_store_svc = service_factory.store
+    mock_store_svc.get_libraries_metadata.side_effect = errors.LibraryError(
+        "One or more declared charm-libs could not be found in the store."
+    )
+
+    # Create the command
+    cmd = FetchLibCommand({"app": APP_METADATA, "services": service_factory})
+
+    # Run with no library argument (library=None)
+    args = argparse.Namespace(library=None, format=None)
+
+    # The command should raise a LibraryError
+    with pytest.raises(errors.LibraryError) as exc_info:
+        cmd.run(args)
+
+    # The error message should NOT contain "Library None not found"
+    # It should contain the actual library name or a more helpful message
+    error_message = str(exc_info.value.args[0])
+    assert "Library None" not in error_message, (
+        f"Error message contains 'Library None': {error_message}"
+    )
+    # We expect the original error message to be preserved or enhanced
+    # The bug was that it was replacing the error with "Library None not found in Charmhub."
+
+
+def test_fetchlibcommand_library_not_found_in_tips(service_factory, monkeypatch):
+    """Test error message when a library is not found in the store tips.
+
+    This tests the second error location where the library ID/API combination
+    is not found in the returned tips from the store.
+    """
+    # Create a mock LibData for a library that exists locally
+    lib_data = LibData(
+        lib_id="6c3e6b6680d64e9c89e611d1a15f65be",
+        api=0,
+        patch=40,
+        content="# Library content",
+        content_hash="abcd1234",
+        full_name="charms.opensearch.v0.helper_charm",
+        path=pathlib.Path("lib/charms/opensearch/v0/helper_charm.py"),
+        lib_name="helper_charm",
+        charm_name="opensearch",
+    )
+
+    # Mock utils.get_libs_from_tree to return our test library
+    mock_get_libs = mock.Mock(return_value=[lib_data])
+    monkeypatch.setattr(
+        "charmcraft.application.commands.store.utils.get_libs_from_tree",
+        mock_get_libs,
+    )
+
+    # Mock the store service to return an empty list (no matching tips)
+    # This simulates the library not being found in Charmhub
+    mock_store_svc = service_factory.store
+    mock_store_svc.get_libraries_metadata.return_value = []
+
+    # Create the command
+    cmd = FetchLibCommand({"app": APP_METADATA, "services": service_factory})
+
+    # Run with no library argument (library=None)
+    args = argparse.Namespace(library=None, format=None)
+
+    # The command should raise a LibraryError
+    with pytest.raises(errors.LibraryError) as exc_info:
+        cmd.run(args)
+
+    # The error message should NOT contain "Library None not found"
+    error_message = str(exc_info.value.args[0])
+    assert "Library None" not in error_message, (
+        f"Error message contains 'Library None': {error_message}"
+    )
+    # We should see the actual library name
+    assert "opensearch" in error_message or "helper_charm" in error_message, (
+        f"Error message should contain library name: {error_message}"
+    )