From 10a36cb60e10594aa5dbf3c5aba6abbd5f6fcd70 Mon Sep 17 00:00:00 2001
From: Alex Hedges <ahedges@isi.edu>
Date: Mon, 17 May 2021 15:30:05 -0400
Subject: [PATCH] Improve decorator factory type signatures

These changes are required to preserve the type signatures of the
created decorators.
---
 src/flask/app.py        | 12 +++++++++---
 src/flask/blueprints.py | 12 +++++++++---
 src/flask/scaffold.py   |  2 +-
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/src/flask/app.py b/src/flask/app.py
index f0f31486..cd1c42ad 100644
--- a/src/flask/app.py
+++ b/src/flask/app.py
@@ -1089,7 +1089,9 @@ class Flask(Scaffold):
             self.view_functions[endpoint] = view_func
 
     @setupmethod
-    def template_filter(self, name: t.Optional[str] = None) -> t.Callable:
+    def template_filter(
+        self, name: t.Optional[str] = None
+    ) -> t.Callable[[TemplateFilterCallable], TemplateFilterCallable]:
         """A decorator that is used to register custom template filter.
         You can specify a name for the filter, otherwise the function
         name will be used. Example::
@@ -1121,7 +1123,9 @@ class Flask(Scaffold):
         self.jinja_env.filters[name or f.__name__] = f
 
     @setupmethod
-    def template_test(self, name: t.Optional[str] = None) -> t.Callable:
+    def template_test(
+        self, name: t.Optional[str] = None
+    ) -> t.Callable[[TemplateTestCallable], TemplateTestCallable]:
         """A decorator that is used to register custom template test.
         You can specify a name for the test, otherwise the function
         name will be used. Example::
@@ -1162,7 +1166,9 @@ class Flask(Scaffold):
         self.jinja_env.tests[name or f.__name__] = f
 
     @setupmethod
-    def template_global(self, name: t.Optional[str] = None) -> t.Callable:
+    def template_global(
+        self, name: t.Optional[str] = None
+    ) -> t.Callable[[TemplateGlobalCallable], TemplateGlobalCallable]:
         """A decorator that is used to register a custom template global function.
         You can specify a name for the global function, otherwise the function
         name will be used. Example::
diff --git a/src/flask/blueprints.py b/src/flask/blueprints.py
index 098eca8c..88883ba7 100644
--- a/src/flask/blueprints.py
+++ b/src/flask/blueprints.py
@@ -387,7 +387,9 @@ class Blueprint(Scaffold):
             )
         )
 
-    def app_template_filter(self, name: t.Optional[str] = None) -> t.Callable:
+    def app_template_filter(
+        self, name: t.Optional[str] = None
+    ) -> t.Callable[[TemplateFilterCallable], TemplateFilterCallable]:
         """Register a custom template filter, available application wide.  Like
         :meth:`Flask.template_filter` but for a blueprint.
 
@@ -417,7 +419,9 @@ class Blueprint(Scaffold):
 
         self.record_once(register_template)
 
-    def app_template_test(self, name: t.Optional[str] = None) -> t.Callable:
+    def app_template_test(
+        self, name: t.Optional[str] = None
+    ) -> t.Callable[[TemplateTestCallable], TemplateTestCallable]:
         """Register a custom template test, available application wide.  Like
         :meth:`Flask.template_test` but for a blueprint.
 
@@ -451,7 +455,9 @@ class Blueprint(Scaffold):
 
         self.record_once(register_template)
 
-    def app_template_global(self, name: t.Optional[str] = None) -> t.Callable:
+    def app_template_global(
+        self, name: t.Optional[str] = None
+    ) -> t.Callable[[TemplateGlobalCallable], TemplateGlobalCallable]:
         """Register a custom template global, available application wide.  Like
         :meth:`Flask.template_global` but for a blueprint.
 
diff --git a/src/flask/scaffold.py b/src/flask/scaffold.py
index f8f94af1..239bc46a 100644
--- a/src/flask/scaffold.py
+++ b/src/flask/scaffold.py
@@ -644,7 +644,7 @@ class Scaffold:
     @setupmethod
     def errorhandler(
         self, code_or_exception: t.Union[t.Type[Exception], int]
-    ) -> t.Callable:
+    ) -> t.Callable[[ErrorHandlerCallable], ErrorHandlerCallable]:
         """Register a function to handle errors by code or exception class.
 
         A decorator that is used to register a function given an