From 6b9edfd05cbe3dd13136d1ad97a248dd5f8751dd Mon Sep 17 00:00:00 2001
From: Santi Cardozo <57201631+scardozos@users.noreply.github.com>
Date: Tue, 25 Oct 2022 15:54:44 +0200
Subject: [PATCH] improve error message if no apps found in registry (#2585)

---
 sanic/app.py      | 9 ++++++++-
 tests/test_app.py | 8 +++++++-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/sanic/app.py b/sanic/app.py
index cb6f76b3..e064f70f 100644
--- a/sanic/app.py
+++ b/sanic/app.py
@@ -1453,7 +1453,14 @@ class Sanic(BaseSanic, StartupMixin, metaclass=TouchUpMeta):
                 return cls.get_app("__mp_main__", force_create=force_create)
             if force_create:
                 return cls(name)
-            raise SanicException(f'Sanic app name "{name}" not found.')
+            raise SanicException(
+                f"Sanic app name '{name}' not found.\n"
+                "App instantiation must occur outside "
+                "if __name__ == '__main__' "
+                "block or by using an AppLoader.\nSee "
+                "https://sanic.dev/en/guide/deployment/app-loader.html"
+                " for more details."
+            )
 
     @classmethod
     def _check_uvloop_conflict(cls) -> None:
diff --git a/tests/test_app.py b/tests/test_app.py
index 0e71f9f7..538fb893 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -347,7 +347,13 @@ def test_app_registry_retrieval_from_multiple():
 
 def test_get_app_does_not_exist():
     with pytest.raises(
-        SanicException, match='Sanic app name "does-not-exist" not found.'
+        SanicException,
+        match="Sanic app name 'does-not-exist' not found.\n"
+            "App instantiation must occur outside "
+            "if __name__ == '__main__' "
+            "block or by using an AppLoader.\nSee "
+            "https://sanic.dev/en/guide/deployment/app-loader.html"
+            " for more details."
     ):
         Sanic.get_app("does-not-exist")