Added SpatialFeatures.unsupported_geojson_options.

django/contrib/gis/db/backends/base/features.py

@@ -51,6 +51,9 @@ class BaseSpatialFeatures:
     # Can SchemaEditor alter geometry fields?
     can_alter_geometry_field = True
 
+    # Set of options that AsGeoJSON() doesn't support.
+    unsupported_geojson_options = {}
+
     @property
     def supports_bbcontains_lookup(self):
         return 'bbcontains' in self.connection.ops.gis_operators

django/contrib/gis/db/backends/mysql/features.py

@@ -14,6 +14,7 @@ class DatabaseFeatures(BaseSpatialFeatures, MySQLDatabaseFeatures):
     supports_transform = False
     supports_null_geometries = False
     supports_num_points_poly = False
+    unsupported_geojson_options = {'crs'}
 
     @cached_property
     def supports_empty_geometry_collection(self):

django/contrib/gis/db/backends/oracle/features.py

@@ -10,3 +10,4 @@ class DatabaseFeatures(BaseSpatialFeatures, OracleDatabaseFeatures):
     supports_geometry_field_unique_index = False
     supports_perimeter_geodetic = True
     supports_dwithin_distance_expr = False
+    unsupported_geojson_options = {'bbox', 'crs', 'precision'}

tests/gis_tests/geoapp/test_functions.py

@@ -44,14 +44,13 @@ class GISFunctionsTests(FuncTestMixin, TestCase):
             '{"type":"Point","crs":{"type":"name","properties":{"name":"EPSG:4326"}},'
             '"bbox":[-87.65018,41.85039,-87.65018,41.85039],"coordinates":[-87.65018,41.85039]}'
         )
-        # MySQL and Oracle ignore the crs option.
-        if mysql or oracle:
+        if 'crs' in connection.features.unsupported_geojson_options:
             del houston_json['crs']
             del chicago_json['crs']
-        # Oracle ignores also the bbox and precision options.
-        if oracle:
+        if 'bbox' in connection.features.unsupported_geojson_options:
             del chicago_json['bbox']
             del victoria_json['bbox']
+        if 'precision' in connection.features.unsupported_geojson_options:
             chicago_json['coordinates'] = [-87.650175, 41.850385]
 
         # Precision argument should only be an integer