python · z764969689 · Jun 2, 2023 · Jun 2, 2023 · Jun 2, 2023 · Jun 2, 2023
diff --git a/Lib/_pyio.py b/Lib/_pyio.py
@@ -2512,8 +2512,11 @@ def read(self, size=None):
         decoder = self._decoder or self._get_decoder()
         if size < 0:
             # Read everything.
+            if (input_chunk := self.buffer.read()) is None and isinstance(self.buffer, BufferedReader):
+                raise BlockingIOError(
+                    "BufferedReader.read() return None, stream opened in non-blocking mode and not data is available")
             result = (self._get_decoded_chars() +
-                      decoder.decode(self.buffer.read(), final=True))
+                      decoder.decode(input_chunk, final=True))
             if self._snapshot is not None:
                 self._set_decoded_chars('')
                 self._snapshot = None

diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
@@ -3995,6 +3995,14 @@ class PyTextIOWrapperTest(TextIOWrapperTest):
     io = pyio
     shutdown_error = "LookupError: unknown encoding: ascii"
 
+    def test_read_non_blocking_stream(self):
+        # Issue #57531
+        # io module doesn't support non-blocking files
+        r = self.MockRawIO((None,))
+        b = self.BufferedReader(r, 1000)
+        t = self.TextIOWrapper(b, encoding="utf-8")
+        self.assertRaises(BlockingIOError, t.read)
+
 
 class IncrementalNewlineDecoderTest(unittest.TestCase):
 

diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-06-02-08-40-32.gh-issue-57531.425aq5.rst b/Misc/NEWS.d/next/Core and Builtins/2023-06-02-08-40-32.gh-issue-57531.425aq5.rst
@@ -0,0 +1 @@
+Add BufferedReader.read() return value check for non-blocking stream mode, raise BlockingIOError instead of TypeError with more context for the caller.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Add BufferedReader.read() return value check for non-blocking stream mode, raise BlockingIOError instead of TypeError with more context for the caller.