[3.12] gh-112064: Fix incorrect handling of negative read sizes in HTTPResponse.read() (GH-128270) (#129396)

gh-112064: Fix incorrect handling of negative read sizes in `HTTPResponse.read()` (GH-128270)

The parameter `amt` of `HTTPResponse.read()`, which could be a negative integer,
has not been handled before and led to waiting for the connection to close
for `keep-alive connections`. Now, this has been fixed, and passing negative values
to `HTTPResponse().read()` works the same as passing `None` value.
(cherry picked from commit 4d0d24f6e3)

Co-authored-by: Yury Manushkin <manushkin@gmail.com>

Lib/http/client.py

@@ -472,7 +472,7 @@ class HTTPResponse(io.BufferedIOBase):
         if self.chunked:
             return self._read_chunked(amt)
 
-        if amt is not None:
+        if amt is not None and amt >= 0:
             if self.length is not None and amt > self.length:
                 # clip the read to the "end of response"
                 amt = self.length
@@ -590,6 +590,8 @@ class HTTPResponse(io.BufferedIOBase):
 
     def _read_chunked(self, amt=None):
         assert self.chunked != _UNKNOWN
+        if amt is not None and amt < 0:
+            amt = None
         value = []
         try:
             while (chunk_left := self._get_chunk_left()) is not None:

Lib/test/test_httplib.py

@@ -1078,6 +1078,25 @@ class BasicTest(TestCase):
         self.assertEqual(resp.read(), expected)
         resp.close()
 
+        # Explicit full read
+        for n in (-123, -1, None):
+            with self.subTest('full read', n=n):
+                sock = FakeSocket(chunked_start + last_chunk + chunked_end)
+                resp = client.HTTPResponse(sock, method="GET")
+                resp.begin()
+                self.assertTrue(resp.chunked)
+                self.assertEqual(resp.read(n), expected)
+                resp.close()
+
+        # Read first chunk
+        with self.subTest('read1(-1)'):
+            sock = FakeSocket(chunked_start + last_chunk + chunked_end)
+            resp = client.HTTPResponse(sock, method="GET")
+            resp.begin()
+            self.assertTrue(resp.chunked)
+            self.assertEqual(resp.read1(-1), b"hello worl")
+            resp.close()
+
         # Various read sizes
         for n in range(1, 12):
             sock = FakeSocket(chunked_start + last_chunk + chunked_end)

Misc/NEWS.d/next/Library/2024-12-26-11-00-03.gh-issue-112064.mCcw3B.rst

@@ -0,0 +1,2 @@
+Fix incorrect handling of negative read sizes in :meth:`HTTPResponse.read
+<http.client.HTTPResponse.read>`. Patch by Yury Manushkin.