From 976da69e79e22c08ba2ea9ffe48bed72bf3290df Mon Sep 17 00:00:00 2001
From: Adam Hopkins <adam@amhopkins.com>
Date: Sun, 9 Jul 2023 10:53:36 +0300
Subject: [PATCH] Add a new exception signal for ALL exceptions raised anywhere
 in application (#2724)

---
 sanic/app.py                  |  4 ++++
 sanic/handlers/error.py       |  4 +++-
 sanic/signals.py              | 12 ++++++++++++
 tests/test_signal_handlers.py | 30 +++++++++++++++++++++++++++---
 4 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/sanic/app.py b/sanic/app.py
index 527650cc..73874239 100644
--- a/sanic/app.py
+++ b/sanic/app.py
@@ -773,6 +773,10 @@ class Sanic(StaticHandleMixin, BaseSanic, StartupMixin, metaclass=TouchUpMeta):
         :raises ServerError: response 500
         """
         response = None
+        await self.dispatch(
+            "server.lifecycle.exception",
+            context={"exception": exception},
+        )
         await self.dispatch(
             "http.lifecycle.exception",
             inline=True,
diff --git a/sanic/handlers/error.py b/sanic/handlers/error.py
index d01f8ba1..0a2ff9a2 100644
--- a/sanic/handlers/error.py
+++ b/sanic/handlers/error.py
@@ -6,7 +6,9 @@ from sanic.errorpages import BaseRenderer, TextRenderer, exception_response
 from sanic.exceptions import ServerError
 from sanic.log import error_logger
 from sanic.models.handler_types import RouteHandler
+from sanic.request.types import Request
 from sanic.response import text
+from sanic.response.types import HTTPResponse
 
 
 class ErrorHandler:
@@ -148,7 +150,7 @@ class ErrorHandler:
                 return text("An error occurred while handling an error", 500)
         return response
 
-    def default(self, request, exception):
+    def default(self, request: Request, exception: Exception) -> HTTPResponse:
         """
         Provide a default behavior for the objects of :class:`ErrorHandler`.
         If a developer chooses to extent the :class:`ErrorHandler` they can
diff --git a/sanic/signals.py b/sanic/signals.py
index 5710f1ed..6b6fdcce 100644
--- a/sanic/signals.py
+++ b/sanic/signals.py
@@ -20,6 +20,7 @@ class Event(Enum):
     SERVER_INIT_BEFORE = "server.init.before"
     SERVER_SHUTDOWN_AFTER = "server.shutdown.after"
     SERVER_SHUTDOWN_BEFORE = "server.shutdown.before"
+    SERVER_LIFECYCLE_EXCEPTION = "server.lifecycle.exception"
     HTTP_LIFECYCLE_BEGIN = "http.lifecycle.begin"
     HTTP_LIFECYCLE_COMPLETE = "http.lifecycle.complete"
     HTTP_LIFECYCLE_EXCEPTION = "http.lifecycle.exception"
@@ -43,6 +44,7 @@ RESERVED_NAMESPACES = {
         Event.SERVER_INIT_BEFORE.value,
         Event.SERVER_SHUTDOWN_AFTER.value,
         Event.SERVER_SHUTDOWN_BEFORE.value,
+        Event.SERVER_LIFECYCLE_EXCEPTION.value,
     ),
     "http": (
         Event.HTTP_LIFECYCLE_BEGIN.value,
@@ -168,6 +170,16 @@ class SignalRouter(BaseRouter):
                     elif maybe_coroutine:
                         return maybe_coroutine
             return None
+        except Exception as e:
+            if self.ctx.app.debug and self.ctx.app.state.verbosity >= 1:
+                error_logger.exception(e)
+
+            if event != Event.SERVER_LIFECYCLE_EXCEPTION.value:
+                await self.dispatch(
+                    Event.SERVER_LIFECYCLE_EXCEPTION.value,
+                    context={"exception": e},
+                )
+            raise e
         finally:
             for signal_event in events:
                 signal_event.clear()
diff --git a/tests/test_signal_handlers.py b/tests/test_signal_handlers.py
index 53eff83f..401353e9 100644
--- a/tests/test_signal_handlers.py
+++ b/tests/test_signal_handlers.py
@@ -1,18 +1,19 @@
 import asyncio
 import os
 import signal
-
 from queue import Queue
 from types import SimpleNamespace
+from typing import Optional
 from unittest.mock import MagicMock
 
 import pytest
-
 from sanic_testing.testing import HOST, PORT
 
+from sanic import Sanic
 from sanic.compat import ctrlc_workaround_for_windows
-from sanic.exceptions import BadRequest
+from sanic.exceptions import BadRequest, ServerError
 from sanic.response import HTTPResponse
+from sanic.signals import Event
 
 
 async def stop(app, loop):
@@ -148,3 +149,26 @@ def test_signals_with_invalid_invocation(app):
         BadRequest, match="Invalid event registration: Missing event name"
     ):
         app.listener(stop)
+
+
+def test_signal_server_lifecycle_exception(app: Sanic):
+    trigger: Optional[Exception] = None
+
+    @app.route("/hello")
+    async def hello_route(request):
+        return HTTPResponse()
+
+    @app.signal(Event.SERVER_LIFECYCLE_EXCEPTION)
+    async def test_signal(exception: Exception):
+        nonlocal trigger
+        trigger = exception
+
+    @app.before_server_start
+    async def test_before_server_start(app):
+        raise ServerError("test_before_server_start")
+
+    with pytest.raises(ServerError, match="test_before_server_start"):
+        app.run(single_process=True)
+
+    assert isinstance(trigger, ServerError)
+    assert str(trigger) == "test_before_server_start"