gh-115997: Make HTTPResponse.read1 and readline raise IncompleteRead

Lib/http/client.py

@@ -663,6 +663,8 @@ def read1(self, n=-1):
         result = self.fp.read1(n)
         if not result and n:
             self._close_conn()
+            if self.length:
+                raise IncompleteRead(result, self.length)
         elif self.length is not None:
             self.length -= len(result)
             if not self.length:
@@ -689,6 +691,8 @@ def readline(self, limit=-1):
         result = self.fp.readline(limit)
         if not result and limit:
             self._close_conn()
+            if self.length:
+                raise IncompleteRead(result, self.length)
         elif self.length is not None:
             self.length -= len(result)
             if not self.length:

Lib/test/test_httplib.py

@@ -1611,6 +1611,40 @@ class ExtendedReadTestContentLengthKnown(ExtendedReadTest):
     _header, _body = ExtendedReadTest.lines.split('\r\n\r\n', 1)
     lines = _header + f'\r\nContent-Length: {len(_body)}\r\n\r\n' + _body
 
+    def _test_incomplete_read(self, read_meth):
+        resp = self.resp
+        # Reduce the size of content the response object will read to
+        # cause the incomplete read.
+        resp.fp.read(1)
+        with self.assertRaises(client.IncompleteRead) as cm:
+            while True:
+                data = read_meth()
+                if not data:
+                    break
+        exception = cm.exception
+        # Unlike `read1` and `readline`, `read` tries to read the whole
+        # content during one call, so it's partial is not empty in this
+        # case.
+        # `read1` and `readline` raise `IncompleteRead` only when they
+        # read 0 bytes before all expected content has been read, so the
+        # partial is empty.
+        if read_meth == self.resp.read:
+            expected_partial = self._body[1:].encode()
+        else:
+            expected_partial = b""
+        self.assertEqual(exception.partial, expected_partial)
+        self.assertEqual(exception.expected, 1)
+        self.assertTrue(resp.isclosed())
+
+    def test_read_incomplete_read(self):
+        self._test_incomplete_read(self.resp.read)
+
+    def test_read1_incomplete_read(self):
+        self._test_incomplete_read(self.resp.read1)
+
+    def test_readline_incomplete_read(self):
+        self._test_incomplete_read(self.resp.readline)
+
 
 class ExtendedReadTestChunked(ExtendedReadTest):
     """

Misc/NEWS.d/next/Library/2024-02-27-20-56-44.gh-issue-115997.LqLP4V.rst

@@ -0,0 +1,4 @@
+Make ``http.client.HTTPResponse.read1`` and
+``http.client.HTTPResponse.readline`` raise :exc:`IncompleteRead` instead of
+returning zero bytes if a connection is closed before an expected number of
+bytes has been read. Patch by Illia Volochii.