From 17d100400fd09f808078e7044aa200427327ab7e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?L=2E=20K=C3=A4rkk=C3=A4inen?=
 <tronic@users.noreply.github.com>
Date: Tue, 10 Mar 2020 16:45:26 +0200
Subject: [PATCH] Middleware and error handling refactoring.

---
 sanic/app.py    | 34 +++++++++++++++++-----------------
 sanic/http.py   | 17 +++++++++++++++++
 sanic/server.py |  9 ++++++---
 3 files changed, 40 insertions(+), 20 deletions(-)

diff --git a/sanic/app.py b/sanic/app.py
index c48a8d20..e42c1210 100644
--- a/sanic/app.py
+++ b/sanic/app.py
@@ -955,22 +955,22 @@ class Sanic:
                 response = HTTPResponse(
                     "An error occurred while handling an error", status=500
                 )
-        # Run response middleware
         if response is not None:
             try:
-                response = await self._run_response_middleware(
-                    request, response, request_name=request.name
-                )
-            except CancelledError:
-                # FIXME: Ensure exiting in a clean manner instead of this
-                # and verify py37 and py38 test_middleware.py separately
-                request.stream.keep_alive = False
-            except Exception:
-                error_logger.exception(
-                    "Exception occurred in one of response "
-                    "middleware handlers"
-                )
-        return response
+                response = await request.respond(response)
+            except:
+                # Skip response middleware
+                request.stream.respond(response)
+                await response.send(end_stream=True)
+                raise
+        else:
+            response = request.stream.response
+        if isinstance(response, BaseHTTPResponse):
+            await response.send(end_stream=True)
+        else:
+            raise ServerError(
+                f"Invalid response type {response!r} (need HTTPResponse)"
+            )
 
     async def handle_request(self, request):
         """Take a request from the HTTP Server and return a response object
@@ -1039,6 +1039,8 @@ class Sanic:
                     response = await response
             if response:
                 response = await request.respond(response)
+            else:
+                response = request.stream.response
             # Make sure that response is finished / run StreamingHTTP callback
             if isinstance(response, BaseHTTPResponse):
                 await response.send(end_stream=True)
@@ -1053,9 +1055,7 @@ class Sanic:
             # -------------------------------------------- #
             # Response Generation Failed
             # -------------------------------------------- #
-            response = await self.handle_exception(request, e)
-            response = await request.respond(response)
-            await response.send(end_stream=True)
+            await self.handle_exception(request, e)
 
     # -------------------------------------------------------------------- #
     # Testing
diff --git a/sanic/http.py b/sanic/http.py
index 5be70957..16a68685 100644
--- a/sanic/http.py
+++ b/sanic/http.py
@@ -274,9 +274,26 @@ class Http:
         # From request and handler states we can respond, otherwise be silent
         if self.stage is Stage.HANDLER:
             app = self.protocol.app
+            if self.request is None:
+                self.create_empty_request()
             response = await app.handle_exception(self.request, exception)
             await self.respond(response).send(end_stream=True)
 
+    def create_empty_request(self):
+        """Current error handling code needs a request object that won't exist
+        if an error occurred during before a request was received. Create a
+        bogus response for error handling use."""
+        # FIXME: Avoid this by refactoring error handling and response code
+        self.request = self.protocol.request_class(
+            url_bytes=self.url.encode() if self.url else b"*",
+            headers=Header({}),
+            version="1.1",
+            method="NONE",
+            transport=self.protocol.transport,
+            app=self.protocol.app,
+        )
+        self.request.stream = self
+
     def log_response(self):
         """
         Helper method provided to enable the logging of responses in case if
diff --git a/sanic/server.py b/sanic/server.py
index cdea56dd..03820844 100644
--- a/sanic/server.py
+++ b/sanic/server.py
@@ -137,6 +137,12 @@ class HttpProtocol(asyncio.Protocol):
         except Exception:
             logger.exception("protocol.connection_task uncaught")
         finally:
+            if self._debug and self._http and self._http.request:
+                ip = self.transport.get_extra_info("peername")
+                logger.error(
+                    "Connection lost before response written"
+                    f" @ {ip} {self._http.request}"
+                )
             self._http = None
             self._task = None
             try:
@@ -229,9 +235,6 @@ class HttpProtocol(asyncio.Protocol):
             self.resume_writing()
             if self._task:
                 self._task.cancel()
-            if self._debug and self._http and self._http.response:
-                ip = self.transport.get_extra_info("peername")
-                logger.error(f"Connection lost before response written @ {ip}")
         except Exception:
             logger.exception("protocol.connection_lost")