Fallback behavior for request parsing when request.POST already acces…

…sed. (#4500)

rest_framework/request.py

@@ -15,6 +15,7 @@
 from django.conf import settings
 from django.http import QueryDict
 from django.http.multipartparser import parse_header
+from django.http.request import RawPostDataException
 from django.utils import six
 from django.utils.datastructures import MultiValueDict
 
@@ -263,19 +264,39 @@ def _load_stream(self):
 
         if content_length == 0:
             self._stream = None
-        elif hasattr(self._request, 'read'):
+        elif not self._request._read_started:
             self._stream = self._request
         else:
-            self._stream = six.BytesIO(self.raw_post_data)
+            self._stream = six.BytesIO(self.body)
+
+    def _supports_form_parsing(self):
+        """
+        Return True if this requests supports parsing form data.
+        """
+        form_media = (
+            'application/x-www-form-urlencoded',
+            'multipart/form-data'
+        )
+        return any([parser.media_type in form_media for parser in self.parsers])
 
     def _parse(self):
         """
         Parse the request content, returning a two-tuple of (data, files)
 
         May raise an `UnsupportedMediaType`, or `ParseError` exception.
         """
-        stream = self.stream
         media_type = self.content_type
+        try:
+            stream = self.stream
+        except RawPostDataException:
+            if not hasattr(self._request, '_post'):
+                raise
+            # If request.POST has been accessed in middleware, and a method='POST'
+            # request was made with 'multipart/form-data', then the request stream
+            # will already have been exhausted.
+            if self._supports_form_parsing():
+                return (self._request.POST, self._request.FILES)
+            stream = None
 
         if stream is None or media_type is None:
             empty_data = QueryDict('', encoding=self._request._encoding)

tests/test_parsers.py

@@ -7,11 +7,16 @@
 from django.core.files.uploadhandler import (
     MemoryFileUploadHandler, TemporaryFileUploadHandler
 )
+from django.http.request import RawPostDataException
 from django.test import TestCase
 from django.utils.six.moves import StringIO
 
 from rest_framework.exceptions import ParseError
-from rest_framework.parsers import FileUploadParser, FormParser
+from rest_framework.parsers import (
+    FileUploadParser, FormParser, JSONParser, MultiPartParser
+)
+from rest_framework.request import Request
+from rest_framework.test import APIRequestFactory
 
 
 class Form(forms.Form):
@@ -122,3 +127,39 @@ def test_get_encoded_filename(self):
 
     def __replace_content_disposition(self, disposition):
         self.parser_context['request'].META['HTTP_CONTENT_DISPOSITION'] = disposition
+
+
+class TestPOSTAccessed(TestCase):
+    def setUp(self):
+        self.factory = APIRequestFactory()
+
+    def test_post_accessed_in_post_method(self):
+        django_request = self.factory.post('/', {'foo': 'bar'})
+        request = Request(django_request, parsers=[FormParser(), MultiPartParser()])
+        django_request.POST
+        assert request.POST == {'foo': ['bar']}
+        assert request.data == {'foo': ['bar']}
+
+    def test_post_accessed_in_post_method_with_json_parser(self):
+        django_request = self.factory.post('/', {'foo': 'bar'})
+        request = Request(django_request, parsers=[JSONParser()])
+        django_request.POST
+        assert request.POST == {}
+        assert request.data == {}
+
+    def test_post_accessed_in_put_method(self):
+        django_request = self.factory.put('/', {'foo': 'bar'})
+        request = Request(django_request, parsers=[FormParser(), MultiPartParser()])
+        django_request.POST
+        assert request.POST == {'foo': ['bar']}
+        assert request.data == {'foo': ['bar']}
+
+    def test_request_read_before_parsing(self):
+        django_request = self.factory.put('/', {'foo': 'bar'})
+        request = Request(django_request, parsers=[FormParser(), MultiPartParser()])
+        django_request.read()
+        with pytest.raises(RawPostDataException):
+            request.POST
+        with pytest.raises(RawPostDataException):
+            request.POST
+            request.data