added create_jinja_loader

CHANGES

@@ -35,6 +35,7 @@ Release date to be announced, codename to be selected
   a decorator.
 - Use Last-Modified for static file sending instead of Date which
   was incorrectly introduced in 0.6.
+- Added `create_jinja_loader` to override the loader creation process.
 
 Version 0.6.1
 -------------

flask/app.py

@@ -352,7 +352,15 @@ class Flask(_PackageBoundObject):
         options = dict(self.jinja_options)
         if 'autoescape' not in options:
             options['autoescape'] = self.select_jinja_autoescape
-        return Environment(loader=_DispatchingJinjaLoader(self), **options)
+        return Environment(loader=self.create_jinja_loader(), **options)
+
+    def create_jinja_loader(self):
+        """Creates the loader for the Jinja2 environment.  Can be used to
+        override just the loader and keeping the rest unchanged.
+
+        .. versionadded:: 0.7
+        """
+        return _DispatchingJinjaLoader(self)
 
     def init_jinja_globals(self):
         """Called directly after the environment was created to inject

tests/flask_tests.py

@@ -857,6 +857,19 @@ class TemplatingTestCase(unittest.TestCase):
         rv = app.test_client().get('/')
         assert rv.data == 'dcba'
 
+    def test_custom_template_loader(self):
+        class MyFlask(flask.Flask):
+            def create_jinja_loader(self):
+                from jinja2 import DictLoader
+                return DictLoader({'index.html': 'Hello Custom World!'})
+        app = MyFlask(__name__)
+        @app.route('/')
+        def index():
+            return flask.render_template('index.html')
+        c = app.test_client()
+        rv = c.get('/')
+        assert rv.data == 'Hello Custom World!'
+
 
 class ModuleTestCase(unittest.TestCase):