Close files when CachingFileManager is garbage collected

Fixes GH2560

This frees users from needing to worry about this.

Author: shoyer

xarray/backends/file_manager.py

@@ -164,6 +164,10 @@ def close(self, needs_lock=True):
         else:
             self._close()
 
+    def __del__(self):
+        # remove files from the cache when garbage collection happens
+        self.close()
+
     def __getstate__(self):
         """State for pickling."""
         lock = None if self._default_lock else self._lock

xarray/backends/h5netcdf_.py

@@ -228,9 +228,6 @@ def prepare_variable(self, name, variable, check_encoding=False,
 
     def sync(self):
         self.ds.sync()
-        # if self.autoclose:
-        #     self.close()
-        # super(H5NetCDFStore, self).sync(compute=compute)
 
     def close(self, **kwargs):
         self._manager.close(**kwargs)

xarray/tests/test_backends_file_manager.py

@@ -1,3 +1,4 @@
+import gc
 import pickle
 import threading
 try:
@@ -38,6 +39,20 @@ def test_file_manager_mock_write(file_cache):
     lock.__enter__.assert_has_calls([mock.call(), mock.call()])
 
 
+def test_file_manager_autoclose(cache):
+    mock_file = mock.Mock()
+    opener = mock.Mock(spec=open, return_value=mock_file)
+    cache = {}
+
+    manager = CachingFileManager(opener, 'filename', cache=cache)
+    manager.acquire()
+    del manager
+    gc.collect()
+
+    assert not cache
+    mock_file.close.assert_called_once_with()
+
+
 def test_file_manager_write_consecutive(tmpdir, file_cache):
     path1 = str(tmpdir.join('testing1.txt'))
     path2 = str(tmpdir.join('testing2.txt'))