Remove old version of FS cache automatically

test/conftest.py

@@ -65,6 +65,18 @@ def pytest_generate_tests(metafunc):
             refactor.collect_dir_tests(base_dir, test_files))
 
 
+@pytest.fixture()
+def isolated_jedi_cache(monkeypatch, tmpdir):
+    """
+    Set `jedi.settings.cache_directory` to a temporary directory during test.
+
+    Same as `clean_jedi_cache`, but create the temporary directory for
+    each test case (scope='function').
+    """
+    settings = base.jedi.settings
+    monkeypatch.setattr(settings, 'cache_directory', str(tmpdir))
+
+
 @pytest.fixture(scope='session')
 def clean_jedi_cache(request):
     """

test/test_cache.py

@@ -1,3 +1,5 @@
+import pytest
+
 from jedi import settings
 from jedi.cache import ParserCacheItem, _ModulePickling
 
@@ -21,10 +23,32 @@ def test_modulepickling_change_cache_dir(monkeypatch, tmpdir):
 
     monkeypatch.setattr(settings, 'cache_directory', dir_1)
     ModulePickling.save_module(path_1, item_1)
-    cached = ModulePickling.load_module(path_1, item_1.change_time - 1)
+    cached = load_stored_item(ModulePickling, path_1, item_1)
     assert cached == item_1.parser
 
     monkeypatch.setattr(settings, 'cache_directory', dir_2)
     ModulePickling.save_module(path_2, item_2)
-    cached = ModulePickling.load_module(path_1, item_1.change_time - 1)
+    cached = load_stored_item(ModulePickling, path_1, item_1)
     assert cached is None
+
+
+def load_stored_item(cache, path, item):
+    """Load `item` stored at `path` in `cache`."""
+    return cache.load_module(path, item.change_time - 1)
+
+
+@pytest.mark.usefixtures("isolated_jedi_cache")
+def test_modulepickling_delete_incompatible_cache():
+    item = ParserCacheItem('fake parser')
+    path = 'fake path'
+
+    cache1 = _ModulePickling()
+    cache1.version = 1
+    cache1.save_module(path, item)
+    cached1 = load_stored_item(cache1, path, item)
+    assert cached1 == item.parser
+
+    cache2 = _ModulePickling()
+    cache2.version = 2
+    cached2 = load_stored_item(cache2, path, item)
+    assert cached2 is None