Fix #1587: add support for handling Expect Header (#1600)

Fix #1587: add support for handling Expect Header

sanic/exceptions.py

@@ -218,6 +218,11 @@ class ContentRangeError(SanicException):
         }
 
 
+@add_status_code(417)
+class HeaderExpectationFailed(SanicException):
+    pass
+
+
 @add_status_code(403)
 class Forbidden(SanicException):
     pass

sanic/request.py

@@ -29,7 +29,7 @@ except ImportError:
 
 
 DEFAULT_HTTP_CONTENT_TYPE = "application/octet-stream"
-
+EXPECT_HEADER = "EXPECT"
 
 # HTTP/1.1: https://www.w3.org/Protocols/rfc2616/rfc2616-sec7.html#sec7.2.1
 # > If the media type remains unknown, the recipient SHOULD treat it

sanic/server.py

@@ -15,6 +15,7 @@ from httptools.parser.errors import HttpParserError
 from multidict import CIMultiDict
 
 from sanic.exceptions import (
+    HeaderExpectationFailed,
     InvalidUsage,
     PayloadTooLarge,
     RequestTimeout,
@@ -22,7 +23,7 @@ from sanic.exceptions import (
     ServiceUnavailable,
 )
 from sanic.log import access_logger, logger
-from sanic.request import Request, StreamBuffer
+from sanic.request import EXPECT_HEADER, Request, StreamBuffer
 from sanic.response import HTTPResponse
 
 
@@ -314,6 +315,10 @@ class HttpProtocol(asyncio.Protocol):
         if self._keep_alive_timeout_handler:
             self._keep_alive_timeout_handler.cancel()
             self._keep_alive_timeout_handler = None
+
+        if self.request.headers.get(EXPECT_HEADER):
+            self.expect_handler()
+
         if self.is_request_stream:
             self._is_stream_handler = self.router.is_stream_handler(
                 self.request
@@ -324,6 +329,21 @@ class HttpProtocol(asyncio.Protocol):
                 )
                 self.execute_request_handler()
 
+    def expect_handler(self):
+        """
+        Handler for Expect Header.
+        """
+        expect = self.request.headers.get(EXPECT_HEADER)
+        if self.request.version == "1.1":
+            if expect.lower() == "100-continue":
+                self.transport.write(b"HTTP/1.1 100 Continue\r\n\r\n")
+            else:
+                self.write_error(
+                    HeaderExpectationFailed(
+                        "Unknown Expect: {expect}".format(expect=expect)
+                    )
+                )
+
     def on_body(self, body):
         if self.is_request_stream and self._is_stream_handler:
             self._request_stream_task = self.loop.create_task(

tests/test_request_stream.py

@@ -1,4 +1,6 @@
+import pytest
 from sanic.blueprints import Blueprint
+from sanic.exceptions import HeaderExpectationFailed
 from sanic.request import StreamBuffer
 from sanic.response import stream, text
 from sanic.views import CompositionView, HTTPMethodView
@@ -40,6 +42,38 @@ def test_request_stream_method_view(app):
     assert response.text == data
 
 
+@pytest.mark.parametrize("headers, expect_raise_exception", [
+({"EXPECT": "100-continue"}, False),
+({"EXPECT": "100-continue-extra"}, True),
+])
+def test_request_stream_100_continue(app, headers, expect_raise_exception):
+    class SimpleView(HTTPMethodView):
+
+        @stream_decorator
+        async def post(self, request):
+            assert isinstance(request.stream, StreamBuffer)
+            result = ""
+            while True:
+                body = await request.stream.read()
+                if body is None:
+                    break
+                result += body.decode("utf-8")
+            return text(result)
+
+    app.add_route(SimpleView.as_view(), "/method_view")
+
+    assert app.is_request_stream is True
+
+    if not expect_raise_exception:
+        request, response = app.test_client.post("/method_view", data=data, headers={"EXPECT": "100-continue"})
+        assert response.status == 200
+        assert response.text == data
+    else:
+        with pytest.raises(ValueError) as e:
+            app.test_client.post("/method_view", data=data, headers={"EXPECT": "100-continue-extra"})
+            assert "Unknown Expect: 100-continue-extra" in str(e)
+
+
 def test_request_stream_app(app):
     """for self.is_request_stream = True and decorators"""