Support calling with_appcontext decorator with parenthesis

Calling without parenthesis still works the same. Just to have a bit more parity with Quart.

CHANGES.rst

@@ -93,7 +93,8 @@ Unreleased
     JSON response like a dict is. :issue:`4672`
 -   When type checking, allow ``TypedDict`` to be returned from view
     functions. :pr:`4695`
-
+-   It is now possible to also call ``@with_appcontext`` decorator
+    with parenthesis, to have additional parity with Quart.
 
 Version 2.1.3
 -------------

src/flask/cli.py

@@ -408,7 +408,7 @@ class ScriptInfo:
 pass_script_info = click.make_pass_decorator(ScriptInfo, ensure=True)
 
 
-def with_appcontext(f):
+def with_appcontext(f=None):
     """Wraps a callback so that it's guaranteed to be executed with the
     script's application context.
 
@@ -416,12 +416,19 @@ def with_appcontext(f):
     ``blueprint.cli`` will always have an app context available, this
     decorator is not required in that case.
 
+    .. versionchanged:: 2.2
+        It is now also possible to call the decorator with parenthesis.
+
     .. versionchanged:: 2.2
         The app context is active for subcommands as well as the
         decorated callback. The app context is always available to
         ``app.cli`` command and parameter callbacks.
     """
 
+    # Decorator was used with parenthesis
+    if f is None:
+        return with_appcontext
+
     @click.pass_context
     def decorator(__ctx, *args, **kwargs):
         if not current_app:

tests/test_cli.py

@@ -341,6 +341,19 @@ def test_with_appcontext(runner):
     assert result.output == "testapp\n"
 
 
+def test_with_appcontext_parenthesis(runner):
+    @click.command()
+    @with_appcontext()
+    def testcmd():
+        click.echo(current_app.name)
+
+    obj = ScriptInfo(create_app=lambda: Flask("testapp"))
+
+    result = runner.invoke(testcmd, obj=obj)
+    assert result.exit_code == 0
+    assert result.output == "testapp\n"
+
+
 def test_appgroup_app_context(runner):
     @click.group(cls=AppGroup)
     def cli():