From 758d609c64404f2b77e2f62e5b33b5cbe55ba0cb Mon Sep 17 00:00:00 2001
From: afonsojanu <afonso@typeble.com>
Date: Mon, 7 Sep 2026 10:45:23 +0100
Subject: [PATCH] Handle read() returning None on a non-blocking socket

Under a non-blocking socket (cheroot supports this via timeout=0),
io.BufferedReader.read() can legitimately return None instead of b''
when there's no data available yet - that's documented behavior in
_pyio's raw IO contract, not an error case.

StreamReader.read() didn't account for this and crashed with
TypeError: object of type 'NoneType' has no len() the moment a
non-blocking read came back empty, which in practice meant it could
blow up mid-request whenever the client hadn't sent anything yet.

Fixes cherrypy/cheroot#278.
---
 cheroot/makefile.py           |  6 +++++-
 cheroot/test/test_makefile.py | 19 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/cheroot/makefile.py b/cheroot/makefile.py
index f5780a1ede..9df2fe2710 100644
--- a/cheroot/makefile.py
+++ b/cheroot/makefile.py
@@ -46,7 +46,11 @@ def __init__(self, sock, mode='r', bufsize=io.DEFAULT_BUFFER_SIZE):
     def read(self, *args, **kwargs):
         """Capture bytes read."""
         val = super().read(*args, **kwargs)
-        self.bytes_read += len(val)
+        # A non-blocking socket with nothing available yet can make the
+        # underlying BufferedReader return None instead of b''. That's
+        # documented io.RawIOBase behavior, so don't choke on it here.
+        if val is not None:
+            self.bytes_read += len(val)
         return val
 
     def has_data(self):
diff --git a/cheroot/test/test_makefile.py b/cheroot/test/test_makefile.py
index d65d4ea268..5fd5f20de7 100644
--- a/cheroot/test/test_makefile.py
+++ b/cheroot/test/test_makefile.py
@@ -1,5 +1,7 @@
 """Tests for :py:mod:`cheroot.makefile`."""
 
+import errno
+
 from cheroot import makefile
 
 
@@ -9,9 +11,12 @@ class MockSocket:
     def __init__(self):
         """Initialize :py:class:`MockSocket`."""
         self.messages = []
+        self.would_block = False
 
     def recv_into(self, buf):
         """Simulate ``recv_into`` for Python 3."""
+        if self.would_block:
+            raise BlockingIOError(errno.EWOULDBLOCK, 'would block')
         if not self.messages:
             return 0
         msg = self.messages.pop(0)
@@ -44,6 +49,20 @@ def test_bytes_read():
     assert rfile.bytes_read == 3
 
 
+def test_read_on_nonblocking_socket_with_no_data():
+    """Reader should return ``None``, not crash, if nothing is available yet.
+
+    A non-blocking socket's ``read()`` can return ``None`` per the
+    documented ``io.RawIOBase`` contract when no data is available; this
+    used to blow up on ``len(None)``. Ref: cherrypy/cheroot#278
+    """
+    sock = MockSocket()
+    sock.would_block = True
+    rfile = makefile.MakeFile(sock, 'r')
+    assert rfile.read(256) is None
+    assert rfile.bytes_read == 0
+
+
 def test_bytes_written():
     """Writer should capture bytes written."""
     sock = MockSocket()