Bugfix blueprint naming

Following discussions for Flask we've decided to name blueprints based
on how they are registered. This allows for two different blueprints
to have the same self-name as long as they are registered in different
nested positions. This helps users choose better blueprint names.

src/flask/app.py

@@ -747,7 +747,7 @@ class Flask(Scaffold):
         ] = self.template_context_processors[None]
         reqctx = _request_ctx_stack.top
         if reqctx is not None:
-            for bp in self._request_blueprints():
+            for bp in request.blueprints:
                 if bp in self.template_context_processors:
                     funcs = chain(funcs, self.template_context_processors[bp])
         orig_ctx = context.copy()
@@ -1267,7 +1267,7 @@ class Flask(Scaffold):
         exc_class, code = self._get_exc_class_and_code(type(e))
 
         for c in [code, None]:
-            for name in chain(self._request_blueprints(), [None]):
+            for name in chain(request.blueprints, [None]):
                 handler_map = self.error_handler_spec[name][c]
 
                 if not handler_map:
@@ -1788,9 +1788,16 @@ class Flask(Scaffold):
         .. versionadded:: 0.7
         """
         funcs: t.Iterable[URLDefaultCallable] = self.url_default_functions[None]
+
         if "." in endpoint:
-            bp = endpoint.rsplit(".", 1)[0]
-            funcs = chain(funcs, self.url_default_functions[bp])
+            bps: t.List[str] = [endpoint.rsplit(".", 1)[0]]
+
+            while "." in bps[-1]:
+                bps.append(bps[-1].rpartition(".")[0])
+
+            for bp in bps:
+                funcs = chain(funcs, self.url_default_functions[bp])
+
         for func in funcs:
             func(endpoint, values)
 
@@ -1831,14 +1838,14 @@ class Flask(Scaffold):
         funcs: t.Iterable[URLValuePreprocessorCallable] = self.url_value_preprocessors[
             None
         ]
-        for bp in self._request_blueprints():
+        for bp in request.blueprints:
             if bp in self.url_value_preprocessors:
                 funcs = chain(funcs, self.url_value_preprocessors[bp])
         for func in funcs:
             func(request.endpoint, request.view_args)
 
         funcs: t.Iterable[BeforeRequestCallable] = self.before_request_funcs[None]
-        for bp in self._request_blueprints():
+        for bp in request.blueprints:
             if bp in self.before_request_funcs:
                 funcs = chain(funcs, self.before_request_funcs[bp])
         for func in funcs:
@@ -1863,7 +1870,7 @@ class Flask(Scaffold):
         """
         ctx = _request_ctx_stack.top
         funcs: t.Iterable[AfterRequestCallable] = ctx._after_request_functions
-        for bp in self._request_blueprints():
+        for bp in request.blueprints:
             if bp in self.after_request_funcs:
                 funcs = chain(funcs, reversed(self.after_request_funcs[bp]))
         if None in self.after_request_funcs:
@@ -1902,7 +1909,7 @@ class Flask(Scaffold):
         funcs: t.Iterable[TeardownCallable] = reversed(
             self.teardown_request_funcs[None]
         )
-        for bp in self._request_blueprints():
+        for bp in request.blueprints:
             if bp in self.teardown_request_funcs:
                 funcs = chain(funcs, reversed(self.teardown_request_funcs[bp]))
         for func in funcs:
@@ -2074,9 +2081,3 @@ class Flask(Scaffold):
         wrapped to apply middleware.
         """
         return self.wsgi_app(environ, start_response)
-
-    def _request_blueprints(self) -> t.Iterable[str]:
-        if _request_ctx_stack.top.request.blueprint is None:
-            return []
-        else:
-            return reversed(_request_ctx_stack.top.request.blueprint.split("."))

src/flask/blueprints.py

@@ -98,7 +98,7 @@ class BlueprintSetupState:
             defaults = dict(defaults, **options.pop("defaults"))
         self.app.add_url_rule(
             rule,
-            f"{self.name_prefix}{self.blueprint.name}.{endpoint}",
+            f"{self.name_prefix}.{self.blueprint.name}.{endpoint}".lstrip("."),
             view_func,
             defaults=defaults,
             **options,
@@ -266,23 +266,24 @@ class Blueprint(Scaffold):
             with.
         :param options: Keyword arguments forwarded from
             :meth:`~Flask.register_blueprint`.
-        :param first_registration: Whether this is the first time this
-            blueprint has been registered on the application.
         """
-        first_registration = False
+        first_registration = True
 
-        if self.name in app.blueprints:
-            assert app.blueprints[self.name] is self, (
-                "A name collision occurred between blueprints"
-                f" {self!r} and {app.blueprints[self.name]!r}."
-                f" Both share the same name {self.name!r}."
-                f" Blueprints that are created on the fly need unique"
-                f" names."
+        for blueprint in app.blueprints.values():
+            if blueprint is self:
+                first_registration = False
+
+        name_prefix = options.get("name_prefix", "")
+        name = f"{name_prefix}.{self.name}".lstrip(".")
+
+        if name in app.blueprints and app.blueprints[name] is not self:
+            raise ValueError(
+                f"Blueprint name '{self.name}' "
+                f"is already registered by {app.blueprints[self.name]}. "
+                "Blueprints must have unique names."
             )
-        else:
-            app.blueprints[self.name] = self
-            first_registration = True
 
+        app.blueprints[name] = self
         self._got_registered_once = True
         state = self.make_setup_state(app, options, first_registration)
 
@@ -298,12 +299,11 @@ class Blueprint(Scaffold):
 
             def extend(bp_dict, parent_dict):
                 for key, values in bp_dict.items():
-                    key = self.name if key is None else f"{self.name}.{key}"
-
+                    key = name if key is None else f"{name}.{key}"
                     parent_dict[key].extend(values)
 
             for key, value in self.error_handler_spec.items():
-                key = self.name if key is None else f"{self.name}.{key}"
+                key = name if key is None else f"{name}.{key}"
                 value = defaultdict(
                     dict,
                     {
@@ -337,7 +337,7 @@ class Blueprint(Scaffold):
             if cli_resolved_group is None:
                 app.cli.commands.update(self.cli.commands)
             elif cli_resolved_group is _sentinel:
-                self.cli.name = self.name
+                self.cli.name = name
                 app.cli.add_command(self.cli)
             else:
                 self.cli.name = cli_resolved_group
@@ -359,7 +359,7 @@ class Blueprint(Scaffold):
             elif state.url_prefix is not None:
                 bp_options["url_prefix"] = state.url_prefix
 
-            bp_options["name_prefix"] = options.get("name_prefix", "") + self.name + "."
+            bp_options["name_prefix"] = name
             blueprint.register(app, bp_options)
 
     def add_url_rule(

src/flask/wrappers.py

@@ -1,6 +1,7 @@
 import typing as t
 
 from werkzeug.exceptions import BadRequest
+from werkzeug.utils import cached_property
 from werkzeug.wrappers import Request as RequestBase
 from werkzeug.wrappers import Response as ResponseBase
 
@@ -77,6 +78,21 @@ class Request(RequestBase):
         else:
             return None
 
+    @cached_property
+    def blueprints(self) -> t.List[str]:
+        """The names of the current blueprint upwards through parent
+        blueprints.
+        """
+        if self.blueprint is None:
+            return []
+
+        bps: t.List[str] = [self.blueprint]
+
+        while "." in bps[-1]:
+            bps.append(bps[-1].rpartition(".")[0])
+
+        return bps
+
     def _load_form_data(self) -> None:
         RequestBase._load_form_data(self)