Support nonblocking pipes on Windows by 1ndahous3 · Pull Request #9110 · RustPython/RustPython

1ndahous3 · 2026-10-14T10:24:51Z

Summary

Implement os.get_blocking and os.set_blocking for Windows pipes.
Report empty reads and full writes as EAGAIN, support partial writes, and preserve FileIO's None result when I/O would block.

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Written with Codex (GPT-6), reviewed by a human before submission.

Summary by CodeRabbit

New Features
- Added Windows named-pipe controls for switching between blocking and non-blocking modes.
Bug Fixes
- Improved Windows pipe read and write behavior when data or buffer capacity is unavailable, including clearer handling of would-block errors.

Assisted-by: Codex:gpt-6

chatgpt-codex-connector · 2026-10-14T10:25:06Z

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-14T17:40:56.949309Z	`2a37faf`	New commits

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coderabbitai · 2026-10-14T10:25:31Z

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Reviewing files that changed from the base of the PR and between 8b3ef11 and 2a37faf.

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extra_tests/snippets/stdlib_os.py

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📝 Walkthrough

Windows CRT I/O now handles specified nonblocking pipe errors, and Windows errno conversion maps EAGAIN to WouldBlock. The host and VM add APIs to read and change named-pipe blocking mode. A Windows-only test checks mode changes and nonblocking pipe I/O.

Changes: Windows pipe I/O

Layer / File(s)	Summary
CRT I/O and error handling `crates/host_env/src/crt_fd.rs`, `crates/host_env/src/os.rs`	Windows writes retry with smaller sizes for the specified `ENOSPC` case. Windows reads map the specified `EINVAL` and `ERROR_NO_DATA` case to `EAGAIN`. Windows `EAGAIN` maps to `WouldBlock`.
Named-pipe blocking controls `crates/host_env/src/nt.rs`, `crates/vm/src/stdlib/nt.rs`, `extra_tests/snippets/stdlib_os.py`	The host and VM add APIs to get and set named-pipe blocking mode. The Windows-only test checks mode changes, zero-length I/O, and `EAGAIN` when reading one byte from an empty nonblocking pipe.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant PythonTest
  participant VMnt
  participant HostNT
  participant NamedPipeHandle
  PythonTest->>VMnt: call set_blocking(fd, blocking)
  VMnt->>HostNT: call set_blocking(fd, blocking)
  HostNT->>NamedPipeHandle: update PIPE_NOWAIT mode
  NamedPipeHandle-->>HostNT: return result
  HostNT-->>VMnt: return result
  VMnt-->>PythonTest: return result or Python exception

Suggested reviewers: youknowone

Merge Risk: ⚪ Minimal · up to 2a37f

The Windows pipe checks are included in the test workflow; no identified issue currently prevents merging.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: adding support for nonblocking Windows pipes.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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github-actions · 2026-10-14T10:26:03Z

📦 Library Dependencies

The following Lib/ modules were modified. Here are their dependencies:

:4: SyntaxWarning: invalid decimal literal
:7: SyntaxWarning: "\z" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\z"? A raw string is also an option.
:10: SyntaxWarning: "\400" is an invalid octal escape sequence. Such sequences will not work in the future. Did you mean "\400"? A raw string is also an option.
:4: SyntaxWarning: invalid decimal literal
:7: SyntaxWarning: "\z" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\z"? A raw string is also an option.
:10: SyntaxWarning: "\400" is an invalid octal escape sequence. Such sequences will not work in the future. Did you mean "\400"? A raw string is also an option.
:4: SyntaxWarning: invalid decimal literal
:7: SyntaxWarning: "\z" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\z"? A raw string is also an option.
:10: SyntaxWarning: "\400" is an invalid octal escape sequence. Such sequences will not work in the future. Did you mean "\400"? A raw string is also an option.
[ ] lib: cpython/Lib/io.py
[ ] lib: cpython/Lib/_pyio.py

dependencies:

io (native: _io, _thread, errno, msvcrt, sys)
- _pyio
- _collections_abc (native: sys)
- abc (native: _abc)
- locale (native: _locale, builtins, encodings.aliases, sys)
- os (native: nt, os.path, posix, sys)
- stat (native: _stat)
- warnings (native: _contextvars, _thread, _warnings, builtins, sys)
- codecs

dependent tests: (108 tests)

io: test__colorize test_android test_argparse test_ast test_asyncio test_base64 test_buffer test_bufio test_builtin test_bz2 test_calendar test_cmd test_cmd_line_script test_codecs test_compile test_compileall test_compiler_assemble test_concurrent_futures test_configparser test_contextlib test_csv test_dbm_dumb test_descr test_dis test_email test_enum test_file test_fileinput test_fileio test_ftplib test_generated_cases test_getpass test_gzip test_hashlib test_http_cookiejar test_httplib test_httpservers test_importlib test_inspect test_io test_json test_largefile test_logging test_lzma test_mailbox test_marshal test_memoryio test_memoryview test_mimetypes test_minidom test_multibytecodec test_optparse test_pathlib test_pdb test_peg_generator test_pickle test_pickletools test_platform test_plistlib test_pprint test_print test_profile test_pstats test_pty test_pulldom test_pydoc test_pyexpat test_pyrepl test_quopri test_regrtest test_robotparser test_sax test_shlex test_shutil test_site test_smtplib test_socket test_socketserver test_subprocess test_support test_sys test_tarfile test_tempfile test_threadedtempfile test_timeit test_tokenize test_traceback test_types test_typing test_unittest test_univnewlines test_urllib test_urllib2 test_uuid test_wave test_webbrowser test_winconsoleio test_wsgiref test_xml_dom_xmlbuilder test_xml_etree test_xml_etree_c test_xmlrpc test_xpickle test_zipapp test_zipfile test_zipimport test_zoneinfo test_zstd

Legend:

[+] path exists in CPython
[x] up-to-date, [ ] outdated

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Actionable comments posted: 1

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Inline comments:
Review comments at @crates/host_env/src/nt.rs:
- Around line 79-97: Update the Windows pipe construction used by pipe() or the
implementation of set_blocking() so the reader handle returned by CreatePipe can
have its blocking mode changed successfully. Use a supported construction that
grants the required access to the read endpoint, or an API compatible with the
CreatePipe handle; preserve the existing blocking-mode behavior.

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Reviewing files that changed from the base of the PR and between 28393e9 and efaf621.

⛔ Files ignored due to path filters: 1

Lib/test/test_io.py is excluded by !Lib/**

📒 Files selected for processing: 5

crates/host_env/src/crt_fd.rs
crates/host_env/src/nt.rs
crates/host_env/src/os.rs
crates/vm/src/stdlib/nt.rs
extra_tests/snippets/stdlib_os.py

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youknowone · 2026-10-14T13:42:42Z

+import io
+
+
+def nonblocking_windows_pipe():


does test_read_non_blocking cover this test? then we usaully don't add original test

Yes, there was overlap. test_read_non_blocking covers the empty-pipe case through TextIOWrapper, and test_nonblock_pipe_write_bigbuf / test_nonblock_pipe_write_smallbuf cover partial/full writes and draining. In 2a37fafd3 I removed those higher-level checks from the snippet. The remaining small test checks Windows pipe blocking-mode toggles and the direct os.read/os.write edge cases, including EAGAIN and zero-length I/O.

Assisted-by: Codex:gpt-6

youknowone

👍

Support nonblocking pipes on Windows

efaf621

Assisted-by: Codex:gpt-6

coderabbitai Bot reviewed Oct 14, 2026

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Comment thread crates/host_env/src/nt.rs

chatgpt-codex-connector Bot reviewed Oct 14, 2026

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Comment thread Lib/test/test_io.py

youknowdot mentioned this pull request Oct 14, 2026

Use 64-bit Windows CRT and FILETIME timestamps #9116

Merged

Merge upstream main

8b3ef11

Assisted-by: Codex:gpt-6

youknowone reviewed Oct 14, 2026

View reviewed changes

Remove redundant Windows pipe test coverage

2a37faf

Assisted-by: Codex:gpt-6

youknowone approved these changes Oct 15, 2026

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youknowone merged commit 0363ff4 into RustPython:main Oct 15, 2026
30 checks passed

1ndahous3 deleted the windows_pipe_nonblocking branch October 15, 2026 09:58

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Support nonblocking pipes on Windows - #9110

Support nonblocking pipes on Windows#9110
youknowone merged 3 commits into
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1ndahous3:windows_pipe_nonblocking

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		import io


		def nonblocking_windows_pipe():

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