[gdal-dev] Intermittent failure with Python mocks

[Jon Morris]

I'm getting intermittent fails with our Python unit tests and I wondered if anyone has seen the same issue. I think it's a race condition where a mock patch is either not applied at all or maybe applied too slowly so the patched function still has its original return value. It might be a pytest issue, but I've now seen it with two different GDAL methods so I'm just curious if anyone has any idea what may be going on.

The first example I reported on Stack Overflow (https://stackoverflow.com/q/75185263/3182496) and looks something like this:

        mock_feat_defn = mocker.patch.object(ogr.FeatureDefn, 'GetFieldCount')
        mock_feat_defn.side_effect = RuntimeError("Some other error message")

        with pytest.raises(RuntimeError, match="Some other error message"):
            get_from_layer_schema(test_lyr, get_names=True, get_types=False)

The second example is this:

        with mock.patch('osgeo.gdal.Driver.Delete', side_effect=None):
            with self.assertRaisesRegex(DatasetError, "Could not delete"):
                delete_path(shp_path)

In both cases we're mocking a GDAL method call to check one of our functions correctly raises an error, but sometimes it works and sometimes it doesn't. If it's not a GDAL issue, no problem, I will keep looking elsewhere for a solution.

Jon

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