Generator/iterator request bodies are never consumed, even after a successful mocked call

CHANGES

@@ -13,6 +13,8 @@ Unreleased
   include the ``params`` and ``req_kwargs`` attributes added by ``responses``.
 * Fixed non-strict `json_params_matcher` raising `TypeError` when an actual
   nested object is compared with an expected scalar value.
+* Fixed a generator/iterator request body not being consumed, leaving it
+  sitting unread even after a successful mocked call. See #713
 
 0.26.3
 ------

responses/__init__.py

@@ -1102,7 +1102,7 @@ def _parse_request_params(self, url: str) -> RequestParams:
         return params
 
     def _read_filelike_body(
-        self, body: Union[str, bytes, BufferedReader, None]
+        self, body: Union[str, bytes, BufferedReader, Iterable[Union[str, bytes]], None]
     ) -> Union[str, bytes, None]:
         # Requests/urllib support multiple types of body, including file-like objects.
         # Read from the file if it's a file-like object to avoid storing a closed file
@@ -1115,6 +1115,11 @@ def _read_filelike_body(
         # https://github.com/urllib3/urllib3/blob/abbfbcb1dd274fc54b4f0a7785fd04d59b634195/src/urllib3/util/request.py#L220
         if hasattr(body, "read") or isinstance(body, BufferedReader):
             return body.read()
+        # Drain a streamed iterator/generator body too, same as a real send would. GH #713.
+        if isinstance(body, Iterable):
+            # urllib3 encodes a str chunk as utf-8 before writing it, same as any other chunk.
+            chunks = (chunk.encode("utf-8") if isinstance(chunk, str) else chunk for chunk in body)
+            return b"".join(chunks)
         return body
 
     def _on_request(

responses/tests/test_responses.py

@@ -2874,3 +2874,48 @@ def run():
 
     run()
     assert_reset()
+
+
+def test_generator_body_in_request():
+    """Validate that a generator/iterator body is fully consumed, the same way a real
+    network send would read it, instead of being stored unconsumed. GH #713.
+    """
+
+    @responses.activate
+    def run():
+        responses.add(responses.POST, "https://example.com")
+
+        def gen():
+            yield b"te"
+            yield b"st"
+
+        generator = gen()
+        requests.post("https://example.com", data=generator)
+
+        assert list(generator) == []
+        assert len(responses.calls) == 1
+        assert responses.calls[0].request.body == b"test"
+
+    run()
+    assert_reset()
+
+
+def test_str_generator_body_in_request():
+    """A generator yielding str chunks is also valid for requests/urllib3 - make sure
+    draining it doesn't raise, and chunks are encoded the same way urllib3 would. GH #713.
+    """
+
+    @responses.activate
+    def run():
+        responses.add(responses.POST, "https://example.com")
+
+        def gen():
+            yield "te"
+            yield "st"
+
+        requests.post("https://example.com", data=gen())
+
+        assert responses.calls[0].request.body == b"test"
+
+    run()
+    assert_reset()