8000 gh-109523: Raise a BlockingIOError if reading text from a non-blockin… · python/cpython@31f16e4 · GitHub
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gh-109523: Raise a BlockingIOError if reading text from a non-blocking stream cannot immediately return bytes. (GH-122933)
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‎Doc/library/io.rst

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@@ -64,6 +64,12 @@ In-memory text streams are also available as :class:`StringIO` objects::
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f = io.StringIO("some initial text data")
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.. note::
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When working with a non-blocking stream, be aware that read operations on text I/O objects
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might raise a :exc:`BlockingIOError` if the stream cannot perform the operation
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immediately.
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The text stream API is described in detail in the documentation of
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:class:`TextIOBase`.
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@@ -770,6 +776,11 @@ than raw I/O does.
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Read and return *size* bytes, or if *size* is not given or negative, until
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EOF or if the read call would block in non-blocking mode.
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.. note::
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When the underlying raw stream is non-blocking, a :exc:`BlockingIOError`
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may be raised if a read operation cannot be completed immediately.
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.. method:: read1(size=-1, /)
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Read and return up to *size* bytes with only one call on the raw stream.
@@ -779,6 +790,10 @@ than raw I/O does.
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.. versionchanged:: 3.7
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The *size* argument is now optional.
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.. note::
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When the underlying raw stream is non-blocking, a :exc:`BlockingIOError`
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may be raised if a read operation cannot be completed immediately.
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.. class:: BufferedWriter(raw, buffer_size=DEFAULT_BUFFER_SIZE)
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@@ -1007,6 +1022,11 @@ Text I/O
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.. versionchanged:: 3.10
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The *encoding* argument now supports the ``"locale"`` dummy encoding name.
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.. note::
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When the underlying raw stream is non-blocking, a :exc:`BlockingIOError`
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may be raised if a read operation cannot be completed immediately.
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:class:`TextIOWrapper` provides these data attributes and methods in
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addition to those from :class:`TextIOBase` and :class:`IOBase`:
< 8000 /td>
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‎Doc/whatsnew/3.14.rst

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@@ -404,6 +404,15 @@ inspect
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(Contributed by Zhikang Yan in :gh:`125634`.)
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io
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--
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* Reading text from a non-blocking stream with ``read`` may now raise a
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:exc:`BlockingIOError` if the operation cannot immediately return bytes.
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(Contributed by Giovanni Siragusa in :gh:`109523`.)
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json
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----
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‎Lib/_pyio.py

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@@ -2545,9 +2545,12 @@ def read(self, size=None):
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size = size_index()
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decoder = self._decoder or self._get_decoder()
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if size < 0:
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chunk = self.buffer.read()
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if chunk is None:
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raise BlockingIOError("Read returned None.")
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# Read everything.
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result = (self._get_decoded_chars() +
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decoder.decode(self.buffer.read(), final=True))
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decoder.decode(chunk, final=True))
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if self._snapshot is not None:
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self._set_decoded_chars('')
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self._snapshot = None

‎Lib/test/test_io.py

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@@ -3932,6 +3932,22 @@ def test_issue35928(self):
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f.write(res)
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self.assertEqual(res + f.readline(), 'foo\nbar\n')
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@unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
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def test_read_non_blocking(self):
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import os
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r, w = os.pipe()
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try:
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os.set_blocking(r, False)
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with self.io.open(r, 'rt') as textfile:
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r = None
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# Nothing has been written so a non-blocking read raises a BlockingIOError exception.
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with self.assertRaises(BlockingIOError):
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textfile.read()
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finally:
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if r is not None:
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os.close(r)
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os.close(w)
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class MemviewBytesIO(io.BytesIO):
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'''A BytesIO object whose read method returns memoryviews

‎Misc/ACKS

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@@ -1736,6 +1736,7 @@ Ng Pheng Siong
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Yann Sionneau
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George Sipe
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J. Sipprell
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Giovanni Siragusa
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Ngalim Siregar
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Kragen Sitaker
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Kaartic Sivaraam

‎Misc/NEWS.d/next/C_API/2024-08-12-10-15-19.gh-issue-109523.S2c3fi.rst

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@@ -0,0 +1 @@
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Reading text from a non-blocking stream with ``read`` may now raise a :exc:`BlockingIOError` if the operation cannot immediately return bytes.

‎Modules/_io/textio.c

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@@ -1992,6 +1992,12 @@ _io_TextIOWrapper_read_impl(textio *self, Py_ssize_t n)
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if (bytes == NULL)
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goto fail;
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if (bytes == Py_None){
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Py_DECREF(bytes);
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PyErr_SetString(PyExc_BlockingIOError, "Read returned None.");
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return NULL;
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}
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_PyIO_State *state = self->state;
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if (Py_IS_TYPE(self->decoder, state->PyIncrementalNewlineDecoder_Type))
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decoded = _PyIncrementalNewlineDecoder_decode(self->decoder,

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