Add a check for request body functions and a test for NotImplementedError.

sanic/app.py

@@ -22,6 +22,7 @@ from sanic.constants import HTTP_METHODS
 from sanic.exceptions import SanicException, ServerError, URLBuildError
 from sanic.handlers import ErrorHandler
 from sanic.log import LOGGING_CONFIG_DEFAULTS, error_logger, logger
+from sanic.request import Request
 from sanic.response import BaseHTTPResponse, HTTPResponse
 from sanic.router import Router
 from sanic.server import (
@@ -61,7 +62,15 @@ class Sanic:
             )
             frame_records = stack()[1]
             name = getmodulename(frame_records[1])
-
+        # Check for unsupported function on custom request objects
+        if request_class and any(hasattr(request_class, m) for m in (
+            "body_init", "body_push", "body_finish"
+        )) and request_class.receive_body is Request.receive_body:
+            raise NotImplementedError(
+                "Request methods body_init, body_push and body_finish "
+                f"are no longer supported. {request_class!r} should "
+                "implement receive_body. It is okay to implement both APIs.",
+            )
         # logging
         if configure_logging:
             logging.config.dictConfig(log_config or LOGGING_CONFIG_DEFAULTS)

tests/test_custom_request.py

@@ -1,10 +1,17 @@
 from io import BytesIO
 
+import pytest
+
 from sanic import Sanic
 from sanic.request import Request
 from sanic.response import json_dumps, text
 
 
+class DeprecCustomRequest(Request):
+    """Using old API should fail when receive_body is not implemented"""
+    def body_push(self, data):
+        pass
+
 class CustomRequest(Request):
     """Alternative implementation for loading body (non-streaming handlers)"""
     async def receive_body(self):
@@ -13,6 +20,14 @@ class CustomRequest(Request):
             buffer.write(data)
         self.body = buffer.getvalue().upper()
         buffer.close()
+    # Old API may be implemented but won't be used here
+    def body_push(self, data):
+        assert False
+
+
+def test_deprecated_custom_request():
+    with pytest.raises(NotImplementedError):
+        Sanic(request_class=DeprecCustomRequest)
 
 def test_custom_request():
     app = Sanic(request_class=CustomRequest)