Fixed #9448 -- `Layer` objects now carry a reference to their parent `DataSource`. Thanks, Matthew D. Hancher for the bug report.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@9284 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/gis/gdal/datasource.py

@@ -111,7 +111,7 @@ class DataSource(object):
             l = get_layer(self._ptr, index)
         else:
             raise TypeError('Invalid index type: %s' % type(index))
-        return Layer(l)
+        return Layer(l, self)
         
     def __len__(self):
         "Returns the number of layers within the data source."

django/contrib/gis/gdal/layer.py

@@ -25,12 +25,18 @@ class Layer(object):
     "A class that wraps an OGR Layer, needs to be instantiated from a DataSource object."
 
     #### Python 'magic' routines ####
-    def __init__(self, layer_ptr):
-        "Needs a C pointer (Python/ctypes integer) in order to initialize."
+    def __init__(self, layer_ptr, ds):
+        """
+        Initializes on an OGR C pointer to the Layer and the `DataSource` object
+        that owns this layer.  The `DataSource` object is required so that a 
+        reference to it is kept with this Layer.  This prevents garbage 
+        collection of the `DataSource` while this Layer is still active.
+        """
         self._ptr = None # Initially NULL
         if not layer_ptr:
             raise OGRException('Cannot create Layer, invalid pointer given')
         self._ptr = layer_ptr
+        self._ds = ds
         self._ldefn = get_layer_defn(self._ptr)
         # Does the Layer support random reading?
         self._random_read = self.test_capability('RandomRead')

django/contrib/gis/tests/test_gdal_ds.py

@@ -130,6 +130,23 @@ class DataSourceTest(unittest.TestCase):
             control_vals = source.field_values[fld_name][sl]
             self.assertEqual(control_vals, test_vals)
 
+    def test03c_layer_references(self):
+        "Test to make sure Layer access is still available without the DataSource."
+        source = ds_list[0]
+
+        # See ticket #9448.
+        def get_layer():
+            # This DataSource object is not accessible outside this
+            # scope.  However, a reference should still be kept alive
+            # on the `Layer` returned.
+            ds = DataSource(source.ds)
+            return ds[0]
+
+        # Making sure we can call OGR routines on the Layer returned.
+        lyr = get_layer()
+        self.assertEqual(source.nfeat, len(lyr))
+        self.assertEqual(source.gtype, lyr.geom_type.num)        
+
     def test04_features(self):
         "Testing Data Source Features."
         for source in ds_list: