Blueprint view function name should not contain dots

CHANGES

@@ -112,6 +112,7 @@ Major release, unreleased
   ``app.debug`` each time. Only one format is used, not different ones
   depending on ``app.debug``. No handlers are removed, and a handler is only
   added if no handlers are already configured. (`#2436`_)
+- Blueprint view function name may not contain dots. (`#2450`_)
 
 .. _#1421: https://github.com/pallets/flask/issues/1421
 .. _#1489: https://github.com/pallets/flask/pull/1489
@@ -144,6 +145,7 @@ Major release, unreleased
 .. _#2416: https://github.com/pallets/flask/pull/2416
 .. _#2430: https://github.com/pallets/flask/pull/2430
 .. _#2436: https://github.com/pallets/flask/pull/2436
+.. _#2450: https://github.com/pallets/flask/pull/2450
 
 Version 0.12.2
 --------------

flask/blueprints.py

@@ -198,6 +198,8 @@ def add_url_rule(self, rule, endpoint=None, view_func=None, **options):
         """
         if endpoint:
             assert '.' not in endpoint, "Blueprint endpoints should not contain dots"
+        if view_func:
+            assert '.' not in view_func.__name__, "Blueprint view function name should not contain dots"
         self.record(lambda s:
             s.add_url_rule(rule, endpoint, view_func, **options))
 

tests/test_blueprints.py

@@ -360,6 +360,15 @@ def foo_foo_foo():
         lambda: None
     )
 
+    foo_foo_foo.__name__ = 'bar.123'
+
+    pytest.raises(
+        AssertionError,
+        lambda: bp.add_url_rule(
+            '/bar/123', view_func=foo_foo_foo
+        )
+    )
+
     app.register_blueprint(bp, url_prefix='/py')
 
     assert client.get('/py/foo').data == b'bp.foo'