Fix PyInstaller shutdown errors on macOS by Ankitsinghsisodya · Pull Request #4930 · psf/black

Ankitsinghsisodya · 2025-12-30T02:38:36Z

In frozen (PyInstaller) builds, disable multiprocessing by limiting workers to 1. This
prevents shutdown errors caused by worker processes attempting to import modules after
PyInstaller cleanup begins.

Fixes #4823

Description

When using the prebuilt Black binary on macOS (built with PyInstaller), users encounter
a FileNotFoundError for base_library.zip during shutdown. This happens because
ProcessPoolExecutor worker processes attempt to import modules after PyInstaller has
begun cleanup of the frozen environment.

The fix adds a check for sys.frozen in reformat_many() to limit workers to 1 in
frozen builds, which forces use of ThreadPoolExecutor instead of
ProcessPoolExecutor. This avoids the shutdown race condition while still allowing
Black to function correctly.

This approach mirrors the existing fallback behavior for environments that don't support
multiprocessing (like AWS Lambda or Termux).

Checklist - did you ...

Implement any code style changes under the --preview style, following the
stability policy?
Add an entry in CHANGES.md if necessary?
Add / update tests if necessary?
Add new / update outdated documentation?

Note on tests: No automated tests can be added for this fix because the issue only
manifests in PyInstaller-frozen builds. The existing test
test_works_in_mono_process_only_environment verifies the mono-process fallback logic
works correctly.

In frozen (PyInstaller) builds, disable multiprocessing by limiting workers to 1. This prevents shutdown errors caused by worker processes attempting to import modules after PyInstaller cleanup begins. Fixes psf#4823

for more information, see https://pre-commit.ci

github-actions · 2025-12-31T17:00:45Z

diff-shades results comparing this PR (c676452) to main (14713ac):

--preview style: no changes

--stable style: no changes

What is this? | Workflow run | diff-shades documentation

cobaltt7 · 2026-01-01T03:16:09Z

Hey @FrankPortman, are you able to test this fix? I've built the mac binary already (build logs)

(25.12.0 binary for comparison)

Copilot

Pull request overview

Fixes a shutdown-time import race in PyInstaller-frozen Black binaries (notably on macOS) by preventing ProcessPoolExecutor usage in frozen environments.

Changes:

In reformat_many(), detect frozen builds via sys.frozen and force workers = 1 to avoid multiprocessing workers.
Add a packaging changelog entry describing the PyInstaller shutdown fix.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
`src/black/concurrency.py`	Forces single-worker execution in frozen builds to avoid `ProcessPoolExecutor` shutdown/import issues.
`CHANGES.md`	Documents the PyInstaller/frozen-build shutdown fix under Packaging.

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

CHANGES.md

src/black/concurrency.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

This reverts commit c676452.

cobaltt7 · 2026-01-23T16:04:34Z

Fuzz error is unrelated to this PR

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: cobalt <61329810+cobaltt7@users.noreply.github.com>

davehughes · 2026-03-05T05:12:01Z

Hey @FrankPortman, are you able to test this fix? I've built the mac binary already (build logs)

(25.12.0 binary for comparison)

Hopefully better late than never - I'm @FrankPortman's teammate and I can confirm that the fix works for me in our Bazel environment. Thank you!

This PR contains the following updates: | Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) | |---|---|---|---| | [black](https://github.com/psf/black) ([changelog](https://github.com/psf/black/blob/main/CHANGES.md)) | `<26.1.1,>=26.1.0` → `<26.3.1,>=26.3.0` | ![age](https://developer.mend.io/api/mc/badges/age/pypi/black/26.3.0?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/black/26.1.0/26.3.0?slim=true) | --- ### Release Notes <details> <summary>psf/black (black)</summary> ### [`v26.3.0`](https://github.com/psf/black/blob/HEAD/CHANGES.md#2630) [Compare Source](psf/black@26.1.0...26.3.0) ##### Stable style - Don't double-decode input, causing non-UTF-8 files to be corrupted ([#4964](psf/black#4964)) - Fix crash on standalone comment in lambda default arguments ([#4993](psf/black#4993)) - Preserve parentheses when `# type: ignore` comments would be merged with other comments on the same line, preventing AST equivalence failures ([#4888](psf/black#4888)) ##### Preview style - Fix bug where `if` guards in `case` blocks were incorrectly split when the pattern had a trailing comma ([#4884](psf/black#4884)) - Fix `string_processing` crashing on unassigned long string literals with trailing commas (one-item tuples) ([#4929](psf/black#4929)) - Simplify implementation of the power operator "hugging" logic ([#4918](psf/black#4918)) ##### Packaging - Fix shutdown errors in PyInstaller builds on macOS by disabling multiprocessing in frozen environments ([#4930](psf/black#4930)) ##### Performance - Introduce winloop for windows as an alternative to uvloop ([#4996](psf/black#4996)) - Remove deprecated function `uvloop.install()` in favor of `uvloop.new_event_loop()` ([#4996](psf/black#4996)) - Rename `maybe_install_uvloop` function to `maybe_use_uvloop` to simplify loop installation and creation of either a uvloop/winloop evenloop or default eventloop ([#4996](psf/black#4996)) ##### Output - Emit a clear warning when the target Python version is newer than the running Python version, since AST safety checks cannot parse newer syntax. Also replace the misleading "INTERNAL ERROR" message with an actionable error explaining the version mismatch ([#4983](psf/black#4983)) ##### *Blackd* - Introduce winloop to be used when windows in use which enables blackd to run faster on windows when winloop is installed. ([#4996](psf/black#4996)) ##### Integrations - Remove unused gallery script ([#5030](psf/black#5030)) - Harden parsing of `black` requirements in the GitHub Action when `use_pyproject` is enabled so that only version specifiers are accepted and direct references such as `black @ https://...` are rejected. Users should upgrade to the latest version of the action as soon as possible. This update is received automatically when using `psf/black@stable`, and is independent of the version of Black installed by the action. ([#5031](psf/black#5031)) ##### Documentation - Expand preview style documentation with detailed examples for `wrap_comprehension_in`, `simplify_power_operator_hugging`, and `wrap_long_dict_values_in_parens` features ([#4987](psf/black#4987)) - Add detailed documentation for formatting Jupyter Notebooks ([#5009](psf/black#5009)) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR is behind base branch, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).  Reviewed-on: https://git.tainton.uk/repos/webexmemebot/pulls/571 Co-authored-by: renovate[bot] <renovate-bot@git.tainton.uk> Co-committed-by: renovate[bot] <renovate-bot@git.tainton.uk>

This PR contains the following updates: | Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) | |---|---|---|---| | [black](https://github.com/psf/black) ([changelog](https://github.com/psf/black/blob/main/CHANGES.md)) | `<26.1.1,>=26.1.0` → `<26.3.1,>=26.3.0` | ![age](https://developer.mend.io/api/mc/badges/age/pypi/black/26.3.0?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/black/26.1.0/26.3.0?slim=true) | --- ### Release Notes <details> <summary>psf/black (black)</summary> ### [`v26.3.0`](https://github.com/psf/black/blob/HEAD/CHANGES.md#2630) [Compare Source](psf/black@26.1.0...26.3.0) ##### Stable style - Don't double-decode input, causing non-UTF-8 files to be corrupted ([#4964](psf/black#4964)) - Fix crash on standalone comment in lambda default arguments ([#4993](psf/black#4993)) - Preserve parentheses when `# type: ignore` comments would be merged with other comments on the same line, preventing AST equivalence failures ([#4888](psf/black#4888)) ##### Preview style - Fix bug where `if` guards in `case` blocks were incorrectly split when the pattern had a trailing comma ([#4884](psf/black#4884)) - Fix `string_processing` crashing on unassigned long string literals with trailing commas (one-item tuples) ([#4929](psf/black#4929)) - Simplify implementation of the power operator "hugging" logic ([#4918](psf/black#4918)) ##### Packaging - Fix shutdown errors in PyInstaller builds on macOS by disabling multiprocessing in frozen environments ([#4930](psf/black#4930)) ##### Performance - Introduce winloop for windows as an alternative to uvloop ([#4996](psf/black#4996)) - Remove deprecated function `uvloop.install()` in favor of `uvloop.new_event_loop()` ([#4996](psf/black#4996)) - Rename `maybe_install_uvloop` function to `maybe_use_uvloop` to simplify loop installation and creation of either a uvloop/winloop evenloop or default eventloop ([#4996](psf/black#4996)) ##### Output - Emit a clear warning when the target Python version is newer than the running Python version, since AST safety checks cannot parse newer syntax. Also replace the misleading "INTERNAL ERROR" message with an actionable error explaining the version mismatch ([#4983](psf/black#4983)) ##### *Blackd* - Introduce winloop to be used when windows in use which enables blackd to run faster on windows when winloop is installed. ([#4996](psf/black#4996)) ##### Integrations - Remove unused gallery script ([#5030](psf/black#5030)) - Harden parsing of `black` requirements in the GitHub Action when `use_pyproject` is enabled so that only version specifiers are accepted and direct references such as `black @ https://...` are rejected. Users should upgrade to the latest version of the action as soon as possible. This update is received automatically when using `psf/black@stable`, and is independent of the version of Black installed by the action. ([#5031](psf/black#5031)) ##### Documentation - Expand preview style documentation with detailed examples for `wrap_comprehension_in`, `simplify_power_operator_hugging`, and `wrap_long_dict_values_in_parens` features ([#4987](psf/black#4987)) - Add detailed documentation for formatting Jupyter Notebooks ([#5009](psf/black#5009)) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR is behind base branch, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).  Reviewed-on: https://git.tainton.uk/repos/pypilot/pulls/421 Reviewed-by: Luke Tainton <luke@tainton.uk> Co-authored-by: renovate[bot] <renovate-bot@git.tainton.uk> Co-committed-by: renovate[bot] <renovate-bot@git.tainton.uk>

This PR contains the following updates: | Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) | |---|---|---|---| | [black](https://github.com/psf/black) ([changelog](https://github.com/psf/black/blob/main/CHANGES.md)) | `<26.1.1,>=26.1.0` → `<26.3.1,>=26.3.0` | ![age](https://developer.mend.io/api/mc/badges/age/pypi/black/26.3.0?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/black/26.1.0/26.3.0?slim=true) | --- ### Release Notes <details> <summary>psf/black (black)</summary> ### [`v26.3.0`](https://github.com/psf/black/blob/HEAD/CHANGES.md#2630) [Compare Source](psf/black@26.1.0...26.3.0) ##### Stable style - Don't double-decode input, causing non-UTF-8 files to be corrupted ([#4964](psf/black#4964)) - Fix crash on standalone comment in lambda default arguments ([#4993](psf/black#4993)) - Preserve parentheses when `# type: ignore` comments would be merged with other comments on the same line, preventing AST equivalence failures ([#4888](psf/black#4888)) ##### Preview style - Fix bug where `if` guards in `case` blocks were incorrectly split when the pattern had a trailing comma ([#4884](psf/black#4884)) - Fix `string_processing` crashing on unassigned long string literals with trailing commas (one-item tuples) ([#4929](psf/black#4929)) - Simplify implementation of the power operator "hugging" logic ([#4918](psf/black#4918)) ##### Packaging - Fix shutdown errors in PyInstaller builds on macOS by disabling multiprocessing in frozen environments ([#4930](psf/black#4930)) ##### Performance - Introduce winloop for windows as an alternative to uvloop ([#4996](psf/black#4996)) - Remove deprecated function `uvloop.install()` in favor of `uvloop.new_event_loop()` ([#4996](psf/black#4996)) - Rename `maybe_install_uvloop` function to `maybe_use_uvloop` to simplify loop installation and creation of either a uvloop/winloop evenloop or default eventloop ([#4996](psf/black#4996)) ##### Output - Emit a clear warning when the target Python version is newer than the running Python version, since AST safety checks cannot parse newer syntax. Also replace the misleading "INTERNAL ERROR" message with an actionable error explaining the version mismatch ([#4983](psf/black#4983)) ##### *Blackd* - Introduce winloop to be used when windows in use which enables blackd to run faster on windows when winloop is installed. ([#4996](psf/black#4996)) ##### Integrations - Remove unused gallery script ([#5030](psf/black#5030)) - Harden parsing of `black` requirements in the GitHub Action when `use_pyproject` is enabled so that only version specifiers are accepted and direct references such as `black @ https://...` are rejected. Users should upgrade to the latest version of the action as soon as possible. This update is received automatically when using `psf/black@stable`, and is independent of the version of Black installed by the action. ([#5031](psf/black#5031)) ##### Documentation - Expand preview style documentation with detailed examples for `wrap_comprehension_in`, `simplify_power_operator_hugging`, and `wrap_long_dict_values_in_parens` features ([#4987](psf/black#4987)) - Add detailed documentation for formatting Jupyter Notebooks ([#5009](psf/black#5009)) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR is behind base branch, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).  Reviewed-on: https://git.tainton.uk/luke/instant-msg-api/pulls/246 Reviewed-by: Luke Tainton <luke@tainton.uk> Co-authored-by: renovate[bot] <renovate-bot@git.tainton.uk> Co-committed-by: renovate[bot] <renovate-bot@git.tainton.uk>

This PR contains the following updates: | Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) | |---|---|---|---| | [black](https://github.com/psf/black) ([changelog](https://github.com/psf/black/blob/main/CHANGES.md)) | `<26.1.1,>=26.1.0` → `<26.3.1,>=26.3.0` | ![age](https://developer.mend.io/api/mc/badges/age/pypi/black/26.3.0?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/black/26.1.0/26.3.0?slim=true) | --- ### Release Notes <details> <summary>psf/black (black)</summary> ### [`v26.3.0`](https://github.com/psf/black/blob/HEAD/CHANGES.md#2630) [Compare Source](psf/black@26.1.0...26.3.0) ##### Stable style - Don't double-decode input, causing non-UTF-8 files to be corrupted ([#4964](psf/black#4964)) - Fix crash on standalone comment in lambda default arguments ([#4993](psf/black#4993)) - Preserve parentheses when `# type: ignore` comments would be merged with other comments on the same line, preventing AST equivalence failures ([#4888](psf/black#4888)) ##### Preview style - Fix bug where `if` guards in `case` blocks were incorrectly split when the pattern had a trailing comma ([#4884](psf/black#4884)) - Fix `string_processing` crashing on unassigned long string literals with trailing commas (one-item tuples) ([#4929](psf/black#4929)) - Simplify implementation of the power operator "hugging" logic ([#4918](psf/black#4918)) ##### Packaging - Fix shutdown errors in PyInstaller builds on macOS by disabling multiprocessing in frozen environments ([#4930](psf/black#4930)) ##### Performance - Introduce winloop for windows as an alternative to uvloop ([#4996](psf/black#4996)) - Remove deprecated function `uvloop.install()` in favor of `uvloop.new_event_loop()` ([#4996](psf/black#4996)) - Rename `maybe_install_uvloop` function to `maybe_use_uvloop` to simplify loop installation and creation of either a uvloop/winloop evenloop or default eventloop ([#4996](psf/black#4996)) ##### Output - Emit a clear warning when the target Python version is newer than the running Python version, since AST safety checks cannot parse newer syntax. Also replace the misleading "INTERNAL ERROR" message with an actionable error explaining the version mismatch ([#4983](psf/black#4983)) ##### *Blackd* - Introduce winloop to be used when windows in use which enables blackd to run faster on windows when winloop is installed. ([#4996](psf/black#4996)) ##### Integrations - Remove unused gallery script ([#5030](psf/black#5030)) - Harden parsing of `black` requirements in the GitHub Action when `use_pyproject` is enabled so that only version specifiers are accepted and direct references such as `black @ https://...` are rejected. Users should upgrade to the latest version of the action as soon as possible. This update is received automatically when using `psf/black@stable`, and is independent of the version of Black installed by the action. ([#5031](psf/black#5031)) ##### Documentation - Expand preview style documentation with detailed examples for `wrap_comprehension_in`, `simplify_power_operator_hugging`, and `wrap_long_dict_values_in_parens` features ([#4987](psf/black#4987)) - Add detailed documentation for formatting Jupyter Notebooks ([#5009](psf/black#5009)) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR is behind base branch, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).  Reviewed-on: https://git.tainton.uk/repos/epage/pulls/208 Reviewed-by: Luke Tainton <luke@tainton.uk> Co-authored-by: renovate[bot] <renovate-bot@git.tainton.uk> Co-committed-by: renovate[bot] <renovate-bot@git.tainton.uk>

This PR contains the following updates: | Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) | |---|---|---|---| | [black](https://github.com/psf/black) ([changelog](https://github.com/psf/black/blob/main/CHANGES.md)) | `<26.1.1,>=26.1.0` → `<26.3.1,>=26.3.0` | ![age](https://developer.mend.io/api/mc/badges/age/pypi/black/26.3.0?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/black/26.1.0/26.3.0?slim=true) | --- ### Release Notes <details> <summary>psf/black (black)</summary> ### [`v26.3.0`](https://github.com/psf/black/blob/HEAD/CHANGES.md#2630) [Compare Source](psf/black@26.1.0...26.3.0) ##### Stable style - Don't double-decode input, causing non-UTF-8 files to be corrupted ([#4964](psf/black#4964)) - Fix crash on standalone comment in lambda default arguments ([#4993](psf/black#4993)) - Preserve parentheses when `# type: ignore` comments would be merged with other comments on the same line, preventing AST equivalence failures ([#4888](psf/black#4888)) ##### Preview style - Fix bug where `if` guards in `case` blocks were incorrectly split when the pattern had a trailing comma ([#4884](psf/black#4884)) - Fix `string_processing` crashing on unassigned long string literals with trailing commas (one-item tuples) ([#4929](psf/black#4929)) - Simplify implementation of the power operator "hugging" logic ([#4918](psf/black#4918)) ##### Packaging - Fix shutdown errors in PyInstaller builds on macOS by disabling multiprocessing in frozen environments ([#4930](psf/black#4930)) ##### Performance - Introduce winloop for windows as an alternative to uvloop ([#4996](psf/black#4996)) - Remove deprecated function `uvloop.install()` in favor of `uvloop.new_event_loop()` ([#4996](psf/black#4996)) - Rename `maybe_install_uvloop` function to `maybe_use_uvloop` to simplify loop installation and creation of either a uvloop/winloop evenloop or default eventloop ([#4996](psf/black#4996)) ##### Output - Emit a clear warning when the target Python version is newer than the running Python version, since AST safety checks cannot parse newer syntax. Also replace the misleading "INTERNAL ERROR" message with an actionable error explaining the version mismatch ([#4983](psf/black#4983)) ##### *Blackd* - Introduce winloop to be used when windows in use which enables blackd to run faster on windows when winloop is installed. ([#4996](psf/black#4996)) ##### Integrations - Remove unused gallery script ([#5030](psf/black#5030)) - Harden parsing of `black` requirements in the GitHub Action when `use_pyproject` is enabled so that only version specifiers are accepted and direct references such as `black @ https://...` are rejected. Users should upgrade to the latest version of the action as soon as possible. This update is received automatically when using `psf/black@stable`, and is independent of the version of Black installed by the action. ([#5031](psf/black#5031)) ##### Documentation - Expand preview style documentation with detailed examples for `wrap_comprehension_in`, `simplify_power_operator_hugging`, and `wrap_long_dict_values_in_parens` features ([#4987](psf/black#4987)) - Add detailed documentation for formatting Jupyter Notebooks ([#5009](psf/black#5009)) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR is behind base branch, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).  Reviewed-on: https://git.tainton.uk/repos/PwnedPW/pulls/326 Reviewed-by: Luke Tainton <luke@tainton.uk> Co-authored-by: renovate[bot] <renovate-bot@git.tainton.uk> Co-committed-by: renovate[bot] <renovate-bot@git.tainton.uk>

This PR contains the following updates: | Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) | |---|---|---|---| | [black](https://github.com/psf/black) ([changelog](https://github.com/psf/black/blob/main/CHANGES.md)) | `<26.1.1,>=26.1.0` → `<26.3.1,>=26.3.0` | ![age](https://developer.mend.io/api/mc/badges/age/pypi/black/26.3.0?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/black/26.1.0/26.3.0?slim=true) | --- ### Release Notes <details> <summary>psf/black (black)</summary> ### [`v26.3.0`](https://github.com/psf/black/blob/HEAD/CHANGES.md#2630) [Compare Source](psf/black@26.1.0...26.3.0) ##### Stable style - Don't double-decode input, causing non-UTF-8 files to be corrupted ([#4964](psf/black#4964)) - Fix crash on standalone comment in lambda default arguments ([#4993](psf/black#4993)) - Preserve parentheses when `# type: ignore` comments would be merged with other comments on the same line, preventing AST equivalence failures ([#4888](psf/black#4888)) ##### Preview style - Fix bug where `if` guards in `case` blocks were incorrectly split when the pattern had a trailing comma ([#4884](psf/black#4884)) - Fix `string_processing` crashing on unassigned long string literals with trailing commas (one-item tuples) ([#4929](psf/black#4929)) - Simplify implementation of the power operator "hugging" logic ([#4918](psf/black#4918)) ##### Packaging - Fix shutdown errors in PyInstaller builds on macOS by disabling multiprocessing in frozen environments ([#4930](psf/black#4930)) ##### Performance - Introduce winloop for windows as an alternative to uvloop ([#4996](psf/black#4996)) - Remove deprecated function `uvloop.install()` in favor of `uvloop.new_event_loop()` ([#4996](psf/black#4996)) - Rename `maybe_install_uvloop` function to `maybe_use_uvloop` to simplify loop installation and creation of either a uvloop/winloop evenloop or default eventloop ([#4996](psf/black#4996)) ##### Output - Emit a clear warning when the target Python version is newer than the running Python version, since AST safety checks cannot parse newer syntax. Also replace the misleading "INTERNAL ERROR" message with an actionable error explaining the version mismatch ([#4983](psf/black#4983)) ##### *Blackd* - Introduce winloop to be used when windows in use which enables blackd to run faster on windows when winloop is installed. ([#4996](psf/black#4996)) ##### Integrations - Remove unused gallery script ([#5030](psf/black#5030)) - Harden parsing of `black` requirements in the GitHub Action when `use_pyproject` is enabled so that only version specifiers are accepted and direct references such as `black @ https://...` are rejected. Users should upgrade to the latest version of the action as soon as possible. This update is received automatically when using `psf/black@stable`, and is independent of the version of Black installed by the action. ([#5031](psf/black#5031)) ##### Documentation - Expand preview style documentation with detailed examples for `wrap_comprehension_in`, `simplify_power_operator_hugging`, and `wrap_long_dict_values_in_parens` features ([#4987](psf/black#4987)) - Add detailed documentation for formatting Jupyter Notebooks ([#5009](psf/black#5009)) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR is behind base branch, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).  Reviewed-on: https://git.tainton.uk/repos/roboluke/pulls/431 Co-authored-by: renovate[bot] <renovate-bot@git.tainton.uk> Co-committed-by: renovate[bot] <renovate-bot@git.tainton.uk>

Ankitsinghsisodya and others added 2 commits December 30, 2025 08:04

Fix PyInstaller shutdown errors on macOS (psf#4930)

e6549cc

In frozen (PyInstaller) builds, disable multiprocessing by limiting workers to 1. This prevents shutdown errors caused by worker processes attempting to import modules after PyInstaller cleanup begins. Fixes psf#4823

[pre-commit.ci] auto fixes from pre-commit.com hooks

e12918b

for more information, see https://pre-commit.ci

Merge branch 'main' into fix-pyinstaller-macos-4823

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Ankitsinghsisodya and others added 3 commits January 23, 2026 08:26

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Update CHANGES.md

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Revert "Update CHANGES.md"

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This reverts commit c676452.

cobaltt7 merged commit 5cdb4b6 into psf:main Jan 23, 2026
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Fix PyInstaller shutdown errors on macOS#4930

Fix PyInstaller shutdown errors on macOS#4930
cobaltt7 merged 6 commits intopsf:mainfrom
Ankitsinghsisodya:fix-pyinstaller-macos-4823

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