Fix AttributeError on store.close() with mypy < 1.20

pytest_mypy_plugins/item.py

@@ -401,7 +401,11 @@ def remove_cache_files(self, fpath_no_suffix: Path) -> None:
                         pass
                 store.commit()
             finally:
-                store.close()
+                # ``MetadataStore.close`` was added in mypy 1.20; guard for older
+                # mypy versions that are still within our supported range (>=1.3).
+                close = getattr(store, "close", None)
+                if close is not None:
+                    close()
 
     def execute_extension_hook(self) -> None:
         extension_hook_fqname = self.config.option.mypy_extension_hook

pytest_mypy_plugins/tests/test_mypy_cache.py

@@ -1,4 +1,5 @@
 import subprocess
+import textwrap
 from collections.abc import Generator
 from pathlib import Path
 from sys import version_info
@@ -184,6 +185,50 @@ def test_cache_files_removed(
     assert not get_created_cache_files(cache_dir, module_fpaths_no_suffix)
 
 
+def test_cache_cleanup_without_store_close(temp_dir: Path) -> None:
+    """Regression test: mypy's ``MetadataStore.close`` was added in 1.20, but
+    ``setup.py`` declares ``mypy>=1.3``. Cache cleanup must not ``AttributeError``
+    on older mypy versions that lack ``close``.
+    """
+    # conftest.py is loaded by the subprocess pytest before the plugin is
+    # imported, stripping ``close`` from the store classes to emulate mypy <1.20.
+    (temp_dir / "conftest.py").write_text(textwrap.dedent("""\
+            from mypy.metastore import (
+                FilesystemMetadataStore,
+                MetadataStore,
+                SqliteMetadataStore,
+            )
+            for cls in (FilesystemMetadataStore, MetadataStore, SqliteMetadataStore):
+                if "close" in cls.__dict__:
+                    delattr(cls, "close")
+            """))
+    make_yaml_test_file(
+        temp_dir,
+        """
+- case: test_cache_cleanup_without_store_close
+  main: |
+    import my_mod
+  files:
+    - path: my_mod.py
+        """,
+    )
+    res = subprocess.run(
+        ["pytest", f"--mypy-testing-base={temp_dir}"],
+        cwd=temp_dir,
+        capture_output=True,
+        text=True,
+    )
+    # The test case itself must pass (or at worst be a test failure), never an
+    # internal error from the plugin's teardown.
+    assert res.returncode in (
+        pytest.ExitCode.OK,
+        pytest.ExitCode.TESTS_FAILED,
+    ), f"rc={res.returncode}\nSTDOUT:\n{res.stdout}\nSTDERR:\n{res.stderr}"
+    combined = res.stdout + res.stderr
+    assert "AttributeError" not in combined, combined
+    assert "has no attribute 'close'" not in combined, combined
+
+
 @pytest.fixture
 def temp_dir() -> Generator[Path]:
     """
@@ -224,6 +269,8 @@ def get_created_cache_files(cache_dir: Path, module_rel_paths_no_suffix: tuple[s
                 if any(entry.startswith(rel_path + ".") for rel_path in module_rel_paths_no_suffix):
                     created.append(entry)
         finally:
-            store.close()
+            close = getattr(store, "close", None)
+            if close is not None:
+                close()
 
     return created