Auto-detect create_app() function in find_best_app() and call if it exists.

flask/cli.py

@@ -46,6 +46,19 @@ def find_best_app(module):
 
     if len(matches) == 1:
         return matches[0]
+
+    # Search for app factory callable.
+    app_factory = getattr(module, 'create_app', None)
+    if app_factory is not None and callable(app_factory):
+        try:
+            app = app_factory()
+            if app is not None and isinstance(app, Flask):
+                return app
+        except TypeError:
+            raise NoAppException('Auto-detected a create_app() function in '
+                                 'module "%s", but could not call it without '
+                                 'specifying arguments.' % module.__name__)
+
     raise NoAppException('Failed to find application in module "%s".  Are '
                          'you sure it contains a Flask application?  Maybe '
                          'you wrapped it in a WSGI middleware or you are '

tests/test_cli.py

@@ -51,6 +51,27 @@ def test_find_best_app(test_apps):
         myapp = Flask('appname')
     assert find_best_app(Module) == Module.myapp
 
+    class Module:
+        @staticmethod
+        def create_app():
+            return Flask('appname')
+    assert isinstance(find_best_app(Module), Flask)
+    assert find_best_app(Module).name == 'appname'
+
+    class Module:
+        myapp = Flask('appname1')
+        @staticmethod
+        def create_app():
+            return Flask('appname2')
+    assert find_best_app(Module) == Module.myapp
+
+    class Module:
+        myapp = Flask('appname1')
+        @staticmethod
+        def create_app(foo):
+            return Flask('appname2')
+    assert find_best_app(Module) == Module.myapp
+
     class Module:
         pass
     pytest.raises(NoAppException, find_best_app, Module)
@@ -60,6 +81,12 @@ def test_find_best_app(test_apps):
         myapp2 = Flask('appname2')
     pytest.raises(NoAppException, find_best_app, Module)
 
+    class Module:
+        @staticmethod
+        def create_app(foo):
+            return Flask('appname2')
+    pytest.raises(NoAppException, find_best_app, Module)
+
 
 def test_prepare_exec_for_file(test_apps):
     """Expect the correct path to be set and the correct module name to be returned.