Add force_create keyword to Sanic.get_app

sanic/app.py

@@ -1424,9 +1424,11 @@ def register_app(cls, app: "Sanic") -> None:
         cls._app_registry[name] = app
 
     @classmethod
-    def get_app(cls, name: str) -> "Sanic":
+    def get_app(cls, name: str, *, force_create: bool = False) -> "Sanic":
         """Retrieve an instantiated Sanic instance"""
         try:
             return cls._app_registry[name]
         except KeyError:
+            if force_create:
+                return cls(name)
             raise SanicException(f'Sanic app name "{name}" not found.')

tests/test_app.py

@@ -295,3 +295,14 @@ def test_app_registry_name_reuse():
 def test_app_registry_retrieval():
     instance = Sanic("test")
     assert Sanic.get_app("test") is instance
+
+
+def test_get_app_does_not_exist():
+    with pytest.raises(SanicException):
+        Sanic.get_app("does-not-exist")
+
+
+def test_get_app_does_not_exist_force_create():
+    assert isinstance(
+        Sanic.get_app("does-not-exist", force_create=True), Sanic
+    )