fix: prepare_body stream detection

Author: k223kim

src/requests/models.py

@@ -596,7 +596,9 @@ def prepare_body(
             if not isinstance(body, bytes):
                 body = body.encode("utf-8")
 
-        if isinstance(data, Iterable) and not isinstance(
+        # Also check hasattr("read") for wrappers that proxy file
+        # methods via __getattr__ (e.g. tqdm.wrapattr)
+        if (isinstance(data, Iterable) or hasattr(data, "read")) and not isinstance(
             data, (str, bytes, list, tuple, Mapping)
         ):
             try:

tests/test_requests.py

@@ -81,6 +81,21 @@
     HAS_PYOPENSSL = False
 
 
+class AttrProxyFileWrapper:
+    """File wrapper that proxies all attribute access via __getattr__.
+
+    Mimics tqdm.utils.CallbackIOWrapper/ObjectWrapper. Has read/tell/seek
+    via the underlying file, but does NOT define __iter__ in its own class,
+    so isinstance(..., Iterable) returns False while hasattr("read") is True.
+    """
+
+    def __init__(self, fileobj):
+        self._fileobj = fileobj
+
+    def __getattr__(self, name):
+        return getattr(self._fileobj, name)
+
+
 class TestRequests:
     digest_auth_algo = ("MD5", "SHA-256", "SHA-512")
 
@@ -2073,6 +2088,82 @@ def __iter__(self):
 
         assert "Unable to rewind request body" in str(e)
 
+    def test_attr_proxy_body_position_is_recorded(self):
+        data = AttrProxyFileWrapper(io.BytesIO(b"the data"))
+        prep = requests.Request("GET", "http://example.com", data=data).prepare()
+        assert prep._body_position == 0
+        assert prep.body is data
+
+    def test_attr_proxy_content_length_is_set(self):
+        data = AttrProxyFileWrapper(io.BytesIO(b"the data"))
+        prep = requests.Request("GET", "http://example.com", data=data).prepare()
+        assert prep.headers["Content-Length"] == "8"
+
+    def test_rewind_attr_proxy_body(self):
+        data = AttrProxyFileWrapper(io.BytesIO(b"the data"))
+        prep = requests.Request("GET", "http://example.com", data=data).prepare()
+        assert prep._body_position == 0
+
+        assert prep.body.read() == b"the data"
+        assert prep.body.read() == b""
+
+        requests.utils.rewind_body(prep)
+        assert prep.body.read() == b"the data"
+
+    def test_rewind_partially_read_attr_proxy_body(self):
+        raw = io.BytesIO(b"the data")
+        raw.read(4)
+        data = AttrProxyFileWrapper(raw)
+        prep = requests.Request("GET", "http://example.com", data=data).prepare()
+        assert prep._body_position == 4
+
+        assert prep.body.read() == b"data"
+
+        requests.utils.rewind_body(prep)
+        assert prep.body.read() == b"data"
+
+    def test_rewind_attr_proxy_body_no_seek(self):
+        class NoSeekWrapper:
+            def __init__(self):
+                pass
+
+            def tell(self):
+                return 0
+
+            def __iter__(self):
+                return iter([])
+
+        data = NoSeekWrapper()
+        prep = requests.Request("GET", "http://example.com", data=data).prepare()
+        assert prep._body_position == 0
+
+        with pytest.raises(UnrewindableBodyError):
+            requests.utils.rewind_body(prep)
+
+    def test_read_only_object_detected_as_stream(self):
+        """An object with read() but no __iter__ should still be a stream."""
+
+        class ReadOnlyFile:
+            def __init__(self, data):
+                self._buf = io.BytesIO(data)
+
+            def read(self, n=-1):
+                return self._buf.read(n)
+
+            def tell(self):
+                return self._buf.tell()
+
+            def seek(self, pos):
+                return self._buf.seek(pos)
+
+            def __len__(self):
+                return self._buf.getbuffer().nbytes
+
+        data = ReadOnlyFile(b"the data")
+        prep = requests.Request("GET", "http://example.com", data=data).prepare()
+        assert prep._body_position == 0
+        assert prep.body is data
+
     def _patch_adapter_gzipped_redirect(self, session, url):
         adapter = session.get_adapter(url=url)
         org_build_response = adapter.build_response