Fixed #13222 -- Made HttpResponse iterable once

response.content can be accessed many times as desired, and always
returns the same result.

iter(response) works only once and consumes the iterator.

django/http/response.py

@@ -283,7 +283,8 @@ class HttpResponse(HttpResponseBase):
                 'deprecated. Use `StreamingHttpResponse` instead '
                 'if you need the streaming behavior.',
                 PendingDeprecationWarning, stacklevel=2)
-        self._iterator = iter(self._container)
+        if not hasattr(self, '_iterator'):
+            self._iterator = iter(self._container)
         return self
 
     def __next__(self):
@@ -303,7 +304,7 @@ class HttpResponse(HttpResponseBase):
 
     def tell(self):
         self._consume_content()
-        return sum(len(chunk) for chunk in self)
+        return len(self.content)
 
 
 class StreamingHttpResponse(HttpResponseBase):

django/test/testcases.py

@@ -596,7 +596,11 @@ class TransactionTestCase(SimpleTestCase):
             msg_prefix + "Couldn't retrieve content: Response code was %d"
             " (expected %d)" % (response.status_code, status_code))
         text = force_text(text, encoding=response._charset)
-        content = b''.join(response).decode(response._charset)
+        if response.streaming:
+            content = b''.join(response.streaming_content)
+        else:
+            content = response.content
+        content = content.decode(response._charset)
         # Avoid ResourceWarning about unclosed files.
         response.close()
         if html:

tests/regressiontests/httpwrappers/tests.py

@@ -337,15 +337,36 @@ class HttpResponseTests(unittest.TestCase):
         self.assertRaises(UnicodeEncodeError,
                           getattr, r, 'content')
 
-        # content can safely be accessed multiple times.
+        # .content can safely be accessed multiple times.
         r = HttpResponse(iter(['hello', 'world']))
         self.assertEqual(r.content, r.content)
         self.assertEqual(r.content, b'helloworld')
+        # accessing the iterator works (once) after accessing .content
+        self.assertEqual(b''.join(r), b'helloworld')
+        self.assertEqual(b''.join(r), b'')
+        # accessing .content still works
+        self.assertEqual(r.content, b'helloworld')
+
+        # XXX accessing .content doesn't work if the response was iterated first
+        # XXX change this when the deprecation completes in HttpResponse
+        r = HttpResponse(iter(['hello', 'world']))
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", PendingDeprecationWarning)
+            self.assertEqual(b''.join(r), b'helloworld')
+        self.assertEqual(r.content, b'')                # not the expected result!
 
         # additional content can be written to the response.
+        r = HttpResponse(iter(['hello', 'world']))
+        self.assertEqual(r.content, b'helloworld')
         r.write('!')
         self.assertEqual(r.content, b'helloworld!')
 
+    def test_iterator_isnt_rewound(self):
+        # Regression test for #13222
+        r = HttpResponse('abc')
+        i = iter(r)
+        self.assertEqual(list(i), [b'abc'])
+        self.assertEqual(list(i), [])
 
     def test_file_interface(self):
         r = HttpResponse()