Scheduled weekly dependency update for week 21 by pyup-bot · Pull Request #441 · fonttools/ufoLib2

pyup-bot · 2026-05-25T15:48:14Z

Update fonttools from 4.62.1 to 4.63.0.

Changelog

4.63.0

----------------------------

- [ttLib] Add support for Apple Color Emoji ``bgcl`` table (4065).
- [ttLib] Add support for ``IFT`` and ``IFTX`` tables (Incremental Font Transfer,
PatchMapFormat2) (4070, 4072).
- [otData] Introduce ``FieldSpec`` dataclass for OpenType table schema definitions,
replacing raw tuples in ``otData.py`` (4076).
- [Feat] Show ``name`` table strings as comments next to label IDs in TTX output,
matching the convention used by ``fvar``, ``STAT``, ``trak`` (4089).
- [cu2qu] Fix Cython complex-division rounding difference in
``split_cubic_into_three`` that could cause ±1 off-curve coordinate shifts
(3928, 4083).
- [designspaceLib] Fix ``map_backward`` for many-to-one (flat-segment) axis maps
that silently dropped entries via dict comprehension
(googlefonts/ufo2ft978, 4085).
- [OS/2] Fix ``setUnicodeRanges`` to accept reserved bits 123-127, restoring
round-trip with ``getUnicodeRanges`` and fixing ``recalcUnicodeRanges`` crash
in the subsetter (4087, 4088).
- [cython] Declare Cython extensions as free-threading compatible on Python 3.13+,
so that importing them on free-threaded Python no longer re-enables the GIL
(4073, 4090).

Links

PyPI: https://pypi.org/project/fonttools
Changelog: https://data.safetycli.com/changelogs/fonttools/
Repo: http://github.com/fonttools/fonttools

Update lxml from 6.1.0 to 6.1.1.

Changelog

6.1.1

==================

Bugs fixed
----------

* The known link attributes in ``lxml.html.defs.link_attrs`` were missing ``xlink:href``,
which can be used for URL bypass attacks in embedded SVG/MathML/etc. content.
https://github.com/fedora-python/lxml_html_clean/security/advisories/GHSA-4jhm-jv67-739f

* The Linux wheels use a patched libxslt 1.1.43, fixing CVE-2025-7424 and CVE-2025-11731.

* The Windows wheels use libxslt 1.1.45, fixing CVE-2025-7424 and CVE-2025-11731.

Links

PyPI: https://pypi.org/project/lxml
Changelog: https://data.safetycli.com/changelogs/lxml/
Homepage: https://lxml.de/

Update orjson from 3.11.7 to 3.11.9.

Changelog

3.11.9

Changed

- Build now depends on Rust 1.95 or later instead of 1.89.

Fixed

- Fix building on Rust 1.95.

3.11.8

Changed

- Build and compatibility improvements.

Links

PyPI: https://pypi.org/project/orjson
Changelog: https://data.safetycli.com/changelogs/orjson/

Update black from 26.3.1 to 26.5.1.

Changelog

26.5.1

Stable style

- Fix unstable formatting of annotated assignments whose subscript annotation contains
an inline comment (e.g. `x: list[   pyright: ignore[...]`) (5130)
- Preserve inline comments (including ` type: ignore`) immediately before a
` fmt: skip` line, avoiding AST equivalence failures (5139)

Packaging

- Correct the version in the published executables (5137)

Documentation

- Add Neovim integration guide covering conform.nvim, ALE, and simple command approaches
(5124)

26.5.0

Highlights

- Add support for unpacking in comprehensions (PEP 798) and for lazy imports (PEP 810),
both new syntactic features in Python 3.15 (5048)
- Python 3.15 is now supported. Compiled wheels are not yet provided for Python 3.15, so
performance may be slower than on existing Python versions. Wheels will be provided
once Python 3.15 is later in its release cycle. (5127)

Stable style

- Fix ` fmt: skip` being ignored in nested `if` expressions with parenthesized `in`
clauses (4903)
- Add syntactic support for Python 3.15 (5048)
- Fix crash when an f-string follows a ` fmt: off` comment inside brackets (5097)
- Preserve multiline compound statement headers when ` fmt: skip` is placed on the
colon line (5117)

Preview style

- Improve heuristics around whether blank lines should appear before, within and after
groups of same-name decorated functions (such as `overload` groups) in `.pyi` stub
files (5021)
- Fix blank lines being removed between a function and a decorated class in `.pyi` stub
files (5092)
- Prevent string merger from creating unsplittable long lines when a pragma comment
(e.g. ` type: ignore`) follows the closing bracket (5096)

Packaging

- Run CI on 3.15 (5127)

Output

- Improve parse error readability by showing multi-line output with an error pointer.
(5068)
- Add `SourceASTParseError` to distinguish source parse failures from internal safety
errors, improving error reporting when Black&#x27;s lenient parser accepts input that
`ast.parse()` rejects (5080)

_Blackd_

- Return HTTP 400 (Bad Request) for source parse failures instead of HTTP 500, keeping
HTTP 500 only for genuine internal safety errors (5080)

Integrations

- Added documentation for doctest formatting tools and updated the integrations index to
match (4916)

Documentation

- Use &quot;Version X.Y.Z&quot; headings in changelog for stable permalink anchors on ReadTheDocs
(5063)
- Note in the editor integrations that the SublimeText `sublack` plugin is archived and
unmaintained (5082)

Links

PyPI: https://pypi.org/project/black
Changelog: https://data.safetycli.com/changelogs/black/

Update click from 8.3.1 to 8.4.1.

Changelog

8.4.1

-------------

Released 2026-05-21

-   ``get_parameter_source()`` is available during eager callbacks and type
 conversion again. :issue:`3458` :issue:`3484`
-   Zsh completion scripts parse correctly on Windows. :issue:`3277` :pr:`3466`
-   Shell completion of `Choice` `Enum` values produces a valid completion
 result. :issue:`3015`
-   Fix empty byte-string handling in echo. :issue:`3487`
-   Fix closed file error with `echo_via_pager`. :issue:`3449`

8.4.0

-------------

Released 2026-05-17

-   :class:`ParamType` typing improvements. :pr:`3371`

 -   :class:`ParamType` is now a generic abstract base class,
     parameterized by its converted value type.
 -   :meth:`~ParamType.convert` return types are narrowed on all
     concrete types (``str`` for :class:`STRING`, ``int`` for
     :class:`INT`, etc.).
 -   :meth:`~ParamType.to_info_dict` returns specific
     :class:`~typing.TypedDict` subclasses instead of
     ``dict[str, Any]``.
 -   :class:`CompositeParamType` and the number-range base are now
     generic with abstract methods.
-   Refactor ``convert_type`` to extract type inference into a private
 ``_guess_type`` helper, and add :func:`typing.overload` signatures.
 :pr:`3372`
-   :class:`Parameter` typing improvements. :pr:`2805`

 -   :class:`Parameter` is now an abstract base class, making explicit
     that it cannot be instantiated directly.
 -   :attr:`Parameter.name` is now ``str`` instead of ``str | None``.
     When ``expose_value=False``, the name is set to ``&quot;&quot;`` instead
     of ``None``.
 -   The ``ctx`` parameter of :meth:`Parameter.get_error_hint` is now
     typed as ``Context | None``, matching the runtime behavior.
-   Split string values from ``default_map`` for parameters with ``nargs &gt; 1``
 or :class:`Tuple` type, matching environment variable behavior.
 :issue:`2745` :pr:`3364`
-   Auto-detect ``type=UNPROCESSED`` for ``flag_value`` of non-basic types
 (not ``str``, ``int``, ``float``, or ``bool``), so programmer-provided
 Python objects like classes and enum members are passed through unchanged
 instead of being stringified. Previously ``type=click.UNPROCESSED`` had
 to be set explicitly. :issue:`2012` :pr:`3363`
-   The error hint now uses :meth:`Command.get_help_option_names` to pick
 non-shadowed help option names, so ``Try &#x27;... -h&#x27;`` no longer points to a
 subcommand option that shadows ``-h``. The longest surviving name is
 shown (``--help`` over ``-h``) for readability. :issue:`2790` :pr:`3208`
-   Fix readline functionality on non-Windows platforms. Prompt text is now
 passed directly to readline instead of being printed separately, allowing
 proper backspace, line editing, and line wrapping behavior. :issue:`2968`
 :pr:`2969`
-   Use :func:`os.startfile` on Windows to open URLs in :func:`open_url`,
 replacing the ``start`` built-in which cannot be invoked without
 ``shell=True``. :issue:`3164` :pr:`3186`
-   Fix Fish shell completion errors when option help text contains newlines.
 :issue:`3043` :pr:`3126`
-   Add :class:`NoSuchCommand` exception with suggestions for misspelled
 commands. :issue:`3107` :pr:`3228`
-   Use :class:`ValueError` message when conversion in :class:`FuncParamType` would
 fail. :issue:`3105` :pr:`3211`
-   Add ``click.get_pager_file`` for file-like access to an output
 pager. :pr:`1572` :pr:`3405`
-   :func:`~click.formatting.wrap_text` now measures line width in visible
 characters, ignoring ANSI escape sequences. :pr:`3420`
-   Fix :meth:`HelpFormatter.write_usage` emitting only a blank line when
 called without ``args``. The usage prefix and program name are now
 written even when no arguments follow, and the trailing separator
 space is stripped so the line ends at the program name.
 :issue:`3360` :pr:`3434`
-   Show custom error messages from types when :func:`prompt` with
 ``hide_input=True`` fails validation, instead of always showing a
 generic message. Built-in type messages mask the input value.
 :issue:`2809` :pr:`3256`
-   Add ``capture`` parameter to :class:`CliRunner` with two modes: ``sys``
 (default) and ``fd``. ``fd`` redirects file descriptors ``1`` and ``2``
 via :func:`os.dup2` so output that bypasses ``sys.stdout`` (stale stream
 references, C extensions, subprocesses, ``faulthandler``) is captured
 with proper isolation. :issue:`854` :issue:`2412` :issue:`2468`
 :issue:`2497` :issue:`2761` :issue:`2827` :issue:`2865` :pr:`3391`
-   Revert the ``8.3.3`` change that exposed the original file descriptor
 via ``fileno()`` on the redirected ``CliRunner`` streams in the default
 capture mode. ``os.dup2(w, sys.stdout.fileno())`` calls inside a CLI no
 longer mutate the host runner&#x27;s stdout, which broke Pytest&#x27;s ``fd``-level
 capture teardown. C-level consumers that need a real ``fd`` should use
 ``capture=&quot;fd&quot;``. :issue:`3384` :pr:`3391`
-   Mark additional built-in strings with ``gettext()`` to extend translation
 coverage. :pr:`2902`
-   Fix feature switch groups (several ``flag_value`` options sharing one
 parameter name) silently dropping an explicit ``default`` when a sibling
 option without an explicit default was declared first. Arbitration is now
 source-aware: a more explicit :class:`ParameterSource` always wins, and
 within ``ParameterSource.DEFAULT``, an option that received an explicit
 ``default=`` keyword wins over a sibling whose default was auto-derived.
 The 8.3.x first-wins fallback for remaining ties was reverted to the
 pre-8.3.x last-wins fallback. :issue:`3403` :pr:`3404`
-   Fix missing space between option help text and the ``(DEPRECATED)``
 label, and localize the option label so it matches the command label.
 The label and the ``DeprecationWarning`` reason suffix are now produced
 by shared helpers. :pr:`3423`
-   Document short option stacking (``-abc`` is parsed as ``-a -b -c``) and
 clarify that multi-character short option names are not supported.
 :issue:`2779` :pr:`3431`

8.3.3

-------------

Released 2026-04-20

-   Use :func:`shlex.split` to split pager and editor commands into ``argv``
 lists for :class:`subprocess.Popen`, removing ``shell=True``.
 :issue:`1026` :pr:`1477` :pr:`2775`
-   Fix ``TypeError`` when rendering help for an option whose default value is
 an object that doesn&#x27;t support equality comparison with strings, such as
 ``semver.Version``. :issue:`3298` :pr:`3299`
-   Fix pager test pollution under parallel execution by using pytest&#x27;s
 ``tmp_path`` fixture instead of a shared temporary file path. :pr:`3238`
-   Treat ``Sentinel.UNSET`` values in a ``default_map`` as absent, so they fall
 through to the next default source instead of being used as the value.
 :issue:`3224` :pr:`3240`
-   Patch ``pdb.Pdb`` in ``CliRunner`` isolation so ``pdb.set_trace()``,
 ``breakpoint()``, and debuggers subclassing ``pdb.Pdb`` (ipdb, pdbpp) can
 interact with the real terminal instead of the captured I/O streams.
 :issue:`654` :issue:`824` :issue:`843` :pr:`951` :pr:`3235`
-   Add optional randomized parallel test execution using ``pytest-randomly`` and
 ``pytest-xdist`` to detect test pollution and race conditions. :pr:`3151`
-   Add contributor documentation for running stress tests, randomized
 parallel tests, and Flask smoke tests. :pr:`3151` :pr:`3177`
-   Show custom ``show_default`` string in prompts, matching the existing
 help text behavior. :issue:`2836` :pr:`2837` :pr:`3165` :pr:`3262` :pr:`3280`
 :pr:`3328`
-   Fix ``default=True`` with boolean ``flag_value`` always returning the
 ``flag_value`` instead of ``True``. The ``default=True`` to ``flag_value``
 substitution now only applies to non-boolean flags, where ``True`` acts as a
 sentinel meaning &quot;activate this flag by default&quot;. For boolean flags,
 ``default=True`` is returned as a literal value. :issue:`3111` :pr:`3239`
-   Mark ``make_default_short_help`` as private API. :issue:`3189` :pr:`3250`
-   ``CliRunner``&#x27;s redirected streams now expose the original file descriptor
 via ``fileno()``, so that ``faulthandler``, ``subprocess``, and other
 C-level consumers no longer crash with ``io.UnsupportedOperation``.
 :issue:`2865`
-   Change :class:`ParameterSource` to an :class:`~enum.IntEnum` and reorder
 its members from most to least explicit, so values can be compared to
 check whether a parameter was explicitly provided. :issue:`2879` :pr:`3248`

8.3.2

-------------

Released 2026-04-02

-   Fix handling of ``flag_value`` when ``is_flag=False`` to allow such options to be
 used without an explicit value. :issue:`3084` :pr:`3152`
-   Hide ``Sentinel.UNSET`` values as ``None`` when using ``lookup_default()``.
 :issue:`3136` :pr:`3199` :pr:`3202` :pr:`3209` :pr:`3212` :pr:`3224`
-   Prevent ``_NamedTextIOWrapper`` from closing streams owned by ``StreamMixer``.
 :issue:`824` :issue:`2991` :issue:`2993` :issue:`3110` :pr:`3139` :pr:`3140`
-   Add comprehensive tests for ``CliRunner`` stream lifecycle, covering
 logging interaction, multi-threaded safety, and sequential invocation
 isolation. Add high-iteration stress tests behind a ``stress`` marker
 with a dedicated CI job. :pr:`3139`
-   Fix callable ``flag_value`` being instantiated when used as a default via
 ``default=True``. :issue:`3121` :pr:`3201` :pr:`3213` :pr:`3225`

Links

PyPI: https://pypi.org/project/click
Changelog: https://data.safetycli.com/changelogs/click/

Update coverage from 7.13.5 to 7.14.0.

Changelog

7.14.0

---------------------------

- Feature: now when running one of the reporting commands, if there are
parallel data files that need combining, they will be implicitly combined
before creating the report. There is no option to avoid the combination; let
us know if you have a use case that requires it.  Thanks, `Tim Hatch
&lt;pull 2162_&gt;`_. Closes `issue 1781`_.

- Fix: the output from ``combine`` was too verbose, listing each file
considered. Now it shows a single line with the counts of files combined,
files skipped, and files with errors. The ``-q`` flag suppresses this line.
The old detailed lines are available with the new ``--debug=combine`` option.

- Fix: running a Python file through a symlink now sets the sys.path correctly,
matching regular Python behavior. Fixes `issue 2157`_.

- Fix: ``Collector.flush_data`` could fail with &quot;RuntimeError: Set changed
size during iteration&quot; when a tracer in another thread added a line to the
per-file set that ``add_lines`` (or ``add_arcs``) was iterating. The values
passed to ``CoverageData`` are now snapshotted via ``dict.copy()`` and
``set.copy()``, which are atomic under the GIL. Thanks, `Alex Vandiver &lt;pull
2165_&gt;`_.

- Fix: the soft keyword ``lazy`` is now bolded in HTML reports.

- We are no longer testing eventlet support. Eventlet started issuing stern
deprecation warnings that break our tests. Our support code is still there.

.. _issue 1781: https://github.com/coveragepy/coveragepy/issues/1781
.. _issue 2157: https://github.com/coveragepy/coveragepy/issues/2157
.. _pull 2162: https://github.com/coveragepy/coveragepy/pull/2162
.. _pull 2165: https://github.com/coveragepy/coveragepy/pull/2165


.. _changes_7-13-5:

Links

PyPI: https://pypi.org/project/coverage
Changelog: https://data.safetycli.com/changelogs/coverage/
Repo: https://github.com/coveragepy/coveragepy

Update librt from 0.8.1 to 0.11.0.

The bot wasn't able to find a changelog for this release. Got an idea?

Links

PyPI: https://pypi.org/project/librt

Update mypy from 1.19.1 to 2.1.0.

Changelog

2.1

We’ve just uploaded mypy 2.1.0 to the Python Package Index ([PyPI](https://pypi.org/project/mypy/)).
Mypy is a static type checker for Python. This release includes new features, performance
improvements and bug fixes. You can install it as follows:

 python3 -m pip install -U mypy

You can read the full documentation for this release on [Read the Docs](http://mypy.readthedocs.io).

librt.vecs: Fast Growable Array Type for Mypyc

The new `librt.vecs` module provides an efficient growable array type `vec` that is
optimized for mypyc use. It provides fast, packed arrays with integer and floating point
value types, which can be **several times faster** than `list`, and tens of times faster
than `array.array` in code compiled using mypyc. It also supports nested `vec` objects and
non-value-type items, such as ``vec[vec[str]]``.

Refer to the [documentation](https://mypyc.readthedocs.io/en/latest/librt_vecs.html) for
the details.

Contributed by Jukka Lehtosalo.

librt.random: Fast Pseudo-Random Number Generation

The new `librt.random` module provides fast pseudo-random number generation that is
optimized for code compiled using mypyc. It can be 3x to 10x faster than the stdlib
`random` module in compiled code.

Refer to the [documentation](https://mypyc.readthedocs.io/en/latest/librt_random.html) for
the details.

Contributed by Jukka Lehtosalo (PR [21433](https://github.com/python/mypy/pull/21433)).

Mypyc Improvements

- Make compilation order with multiple files consistent (Piotr Sawicki, PR [21419](https://github.com/python/mypy/pull/21419))
- Fix crash on accessing `StopAsyncIteration` (Piotr Sawicki, PR [21406](https://github.com/python/mypy/pull/21406))
- Fix incremental compilation with `separate` flag (Vaggelis Danias, PR [21299](https://github.com/python/mypy/pull/21299))

Fixes to Crashes

- Fix crash on partial type with `--allow-redefinition` and `global` declaration (Jukka Lehtosalo, PR [21428](https://github.com/python/mypy/pull/21428))
- Fix broken awaitable generator patching (Ivan Levkivskyi, PR [21435](https://github.com/python/mypy/pull/21435))

Changes to Messages

- Fix function call error message for small number of arguments (sobolevn, PR [21432](https://github.com/python/mypy/pull/21432))

Other Notable Fixes and Improvements

- Rely on typeshed stubs for `slice` typing (Ivan Levkivskyi, PR [21401](https://github.com/python/mypy/pull/21401))
- Improve negative narrowing for membership checks on tuples (Shantanu, PR [21456](https://github.com/python/mypy/pull/21456))
- Narrow match captures based on previous cases (Shantanu, PR [21405](https://github.com/python/mypy/pull/21405))
- Fix nondeterminism in overload resolution (Shantanu, PR [21455](https://github.com/python/mypy/pull/21455))
- Respect file config comments for stale modules (Adam Turner, PR [21444](https://github.com/python/mypy/pull/21444))
- Fix JSON output mode for syntax errors in parallel mode (Adam Turner, PR [21434](https://github.com/python/mypy/pull/21434))
- Fix type variable with values as a supertype (Ivan Levkivskyi, PR [21431](https://github.com/python/mypy/pull/21431))
- Add support for configuring `--num-workers` with an environment variable (Kevin Kannammalil, PR [21407](https://github.com/python/mypy/pull/21407))
- Respect JSON output mode for syntax errors (Adam Turner, PR [21386](https://github.com/python/mypy/pull/21386))
- Analyze `TypedDict` decorators (Pranav Manglik, PR [21267](https://github.com/python/mypy/pull/21267))

Typeshed Updates

Please see [git log](https://github.com/python/typeshed/commits/main?after=e4d32e01bee44241a5e7c33298c261175b9f1bdb+0&amp;branch=main&amp;path=stdlib) for full list of standard library typeshed stub changes.

Acknowledgements

Thanks to all mypy contributors who contributed to this release:

- Adam Turner
- Ivan Levkivskyi
- Jukka Lehtosalo
- Kevin Kannammalil
- Piotr Sawicki
- Shantanu
- sobolevn
- Vaggelis Danias

I’d also like to thank my employer, Dropbox, for supporting mypy development.

2.0

We’ve just uploaded mypy 2.0.0 to the Python Package Index ([PyPI](https://pypi.org/project/mypy/)).
Mypy is a static type checker for Python. This release includes new features, performance
improvements and bug fixes. There are also changes to options and defaults.
You can install it as follows:

 python3 -m pip install -U mypy

You can read the full documentation for this release on [Read the Docs](http://mypy.readthedocs.io).

Enable `--local-partial-types` by Default

This flag affects the inference of types based on assignments in other scopes.
For now, explicitly disabling this continues to be supported, but this support will be removed
in the future as the legacy behaviour is hard to support with other current and future features
in mypy, like the daemon or the new implementation of flexible redefinitions.

Contributed by Ivan Levkivskyi, Jukka Lehtosalo, Shantanu in [PR 21163](https://github.com/python/mypy/pull/21163).

Enable `--strict-bytes` by Default

Per [PEP 688](https://peps.python.org/pep-0688), mypy no longer treats `bytearray` and `memoryview`
values as assignable to the `bytes` type.

Contributed by Shantanu in [PR 18371](https://github.com/python/mypy/pull/18371).

New Behavior for `--allow-redefinition`

The `--allow-redefinition` flag now behaves like `--allow-redefinition-new` in mypy 1.20
and earlier. The new behavior is generally more flexible. For example, you can have different
types for a variable in different blocks:

python
mypy: allow-redefinition

def foo(cond: bool) -&gt; None:
 if cond:
     for x in [&quot;a&quot;, &quot;b&quot;]:
          Type of &quot;x&quot; is &quot;str&quot; here
         ...
 else:
     for x in [1, 2]:
          Type of &quot;x&quot; is &quot;int&quot; here
         ...


The new behavior requires `--local-partial-types`, which is now enabled by default.

However, `--allow-redefinition` doesn&#x27;t allow giving two type annotations for the same
variable. The old behavior (sometimes) allows this. Code like this now generates an error
when using `--allow-redefinition`:

python
def foo() -&gt; None:
 x: list[int] = []
 ...
 x: list[str] = []   Error: &quot;x&quot; redefined
 ...


You can still use `--allow-redefinition-old` to fall back to the old behavior. We have no
plans to remove the legacy behavior, but the old functionality is maintained on a best effort
basis.

Contributed by Jukka Lehtosalo in [PR 21276](https://github.com/python/mypy/pull/21276).

Parallel Type Checking

Mypy now supports experimental parallel and incremental type checking. Use `--num-workers N`
or `-nN` to use `N` worker processes to type check in parallel. The speedup depends on the
import structure of your codebase and your environment, but for large projects we&#x27;ve seen
performance gains of **up to 5x** when using 8 worker processes.

Parallel type checking implicitly enables the new native parser. There are still some
minor semantic differences between parallel and non-parallel modes, which we will be fixing
in future mypy releases.

Contributed by Ivan Levkivskyi, with additional contributions from Emma Smith and Jukka
Lehtosalo.

Recent related changes since the last release:

- Freeze garbage collection in parallel workers for 4-5% speedup (Ivan Levkivskyi, PR [21302](https://github.com/python/mypy/pull/21302))
- Expose `--num-workers` and `--native-parser` (Ivan Levkivskyi, PR [21387](https://github.com/python/mypy/pull/21387))
- Split type checking into interface and implementation in parallel workers (Ivan Levkivskyi, PR [21119](https://github.com/python/mypy/pull/21119))
- Batch module groups for parallel processing (Ivan Levkivskyi, PR [21287](https://github.com/python/mypy/pull/21287))
- Optimize parallel worker startup (Ivan Levkivskyi, PR [21203](https://github.com/python/mypy/pull/21203))
- Parse files in parallel when possible (Ivan Levkivskyi, PR [21175](https://github.com/python/mypy/pull/21175))
- Use parallel parsing at all stages (Ivan Levkivskyi, PR [21266](https://github.com/python/mypy/pull/21266))
- Fix sequential bottleneck in parallel parsing (Jukka Lehtosalo, PR [21291](https://github.com/python/mypy/pull/21291))
- Fail fast when a user tries to generate reports with parallel workers (Ivan Levkivskyi, PR [21341](https://github.com/python/mypy/pull/21341))
- Partially support old NumPy plugin in parallel type checking (Ivan Levkivskyi, PR [21324](https://github.com/python/mypy/pull/21324))
- Handle reachability consistently in parallel type checking (Ivan Levkivskyi, PR [21322](https://github.com/python/mypy/pull/21322))
- Always respect `no_type_check` in parallel type checking (Ivan Levkivskyi, PR [21320](https://github.com/python/mypy/pull/21320))
- Minor fixes in parallel checking (Ivan Levkivskyi, PR [21319](https://github.com/python/mypy/pull/21319))
- Fix plugin logic in parallel type checking (Ivan Levkivskyi, PR [21252](https://github.com/python/mypy/pull/21252))
- Fix Windows IPC race condition when using parallel checking (Jukka Lehtosalo, PR [21228](https://github.com/python/mypy/pull/21228))
- Report parallel worker exit status on receive failure (Jukka Lehtosalo, PR [21224](https://github.com/python/mypy/pull/21224))

Drop Support for Targeting Python 3.9

Mypy no longer supports type checking code with `--python-version 3.9`.
Use `--python-version 3.10` or newer.

Contributed by Shantanu, Marc Mueller in [PR 21243](https://github.com/python/mypy/pull/21243).

Remove Special Casing of Legacy Bundled Stubs

Mypy used to bundle stubs for a few packages in versions 0.812 and earlier. To navigate the
transition, mypy used to report missing types for these packages even if `--ignore-missing-imports`
was set. Mypy now consistently respects `--ignore-missing-imports` for all packages.

Contributed by Shantanu in [PR 18372](https://github.com/python/mypy/pull/18372).

Prevent Assignment to None for Non-Optional Class Variables with Type Comments

Mypy used to allow assignment to None for class variables when using type comments. This was a
common idiom in Python 3.5 and earlier, prior to the introduction of variable annotations.
However, this was a soundness hole and has now been removed.

Contributed by Shantanu in [PR 20054](https://github.com/python/mypy/pull/20054).

librt.strings: String and Bytes Primitives for Mypyc

In mypy 1.20, we introduced [librt](https://pypi.org/project/librt/) as a standard library
for mypyc that fills in some gaps in the Python standard library and the C API.
This release adds the new module `librt.strings`, which contains utilities for building
string and bytes objects, and for accessing and generating binary data:

* `StringWriter` and `BytesWriter` classes allow quickly building `str` and `bytes` objects
from parts.
* `read_*` and `write_*` functions provide fast reading and writing of binary-encoded data.

Refer to the [documentation](https://mypyc.readthedocs.io/en/latest/librt_strings.html) for
the details.

Contributed by Jukka Lehtosalo.

Mypyc Improvements

- Document `librt.time` (Jukka Lehtosalo, PR [21372](https://github.com/python/mypy/pull/21372))
- Mark `librt.time.time()` non-experimental (Ivan Levkivskyi, PR [21310](https://github.com/python/mypy/pull/21310))
- Fix `librt.time` primitive now that it is no longer experimental (Ivan Levkivskyi, PR [21318](https://github.com/python/mypy/pull/21318))
- Fix `librt` API/ABI version checks (Jukka Lehtosalo, PR [21311](https://github.com/python/mypy/pull/21311))
- Generate more type methods for classes with attribute dictionaries (Piotr Sawicki, PR [21290](https://github.com/python/mypy/pull/21290))
- Fix reference counting for tuple items during deallocation (Shantanu, PR [21245](https://github.com/python/mypy/pull/21245))
- Release new instances when `__init__` raises (Shantanu, PR [21248](https://github.com/python/mypy/pull/21248))
- Fix `property` getter memory leak (Vaggelis Danias, PR [21230](https://github.com/python/mypy/pull/21230))
- Fix semantics for walrus expression in tuple (Shantanu, PR [21249](https://github.com/python/mypy/pull/21249))
- Fix crash on import errors during cleanup (Shantanu, PR [21247](https://github.com/python/mypy/pull/21247))
- Fix reference leak in str index (Shantanu, PR [21251](https://github.com/python/mypy/pull/21251))
- Fix memory leak in integer true division (Shantanu, PR [21246](https://github.com/python/mypy/pull/21246))
- Fix reference leaks in `list.clear()`/`dict.clear()` (Shantanu, PR [21244](https://github.com/python/mypy/pull/21244))
- Resolve type aliases in function specialization (esarp, PR [21233](https://github.com/python/mypy/pull/21233))
- Report an error if an acyclic class inherits from non-acyclic (Piotr Sawicki, PR [21227](https://github.com/python/mypy/pull/21227))
- Fix `b64decode` to match new CPython behavior (Piotr Sawicki, PR [21200](https://github.com/python/mypy/pull/21200))

Fixes to Crashes

- Fix crash when a file does not exist during semantic analysis (Ivan Levkivskyi, PR [21379](https://github.com/python/mypy/pull/21379))
- Fix parallel worker crash on syntax error (Ivan Levkivskyi, PR [21202](https://github.com/python/mypy/pull/21202))

Changes to Messages

- Improve error messages for unexpected keyword arguments in overloaded functions (Kevin Kannammalil, PR [20592](https://github.com/python/mypy/pull/20592))
- Don&#x27;t suggest `Foo[...]` when `Foo(arg=...)` is used in annotation (Yosof Badr, PR [21238](https://github.com/python/mypy/pull/21238))
- Mention what codes are actually ignored in &quot;not covered by type: ignore comment&quot; note (wyattscarpenter, PR [19904](https://github.com/python/mypy/pull/19904))
- Improve error messages when positional argument is missing (Kevin Kannammalil, PR [20591](https://github.com/python/mypy/pull/20591))
- Improve &quot;name is not defined&quot; errors with fuzzy matching (Kevin Kannammalil, PR [20693](https://github.com/python/mypy/pull/20693))
- Add suggestions for misspelled module imports (Kevin Kannammalil, PR [20695](https://github.com/python/mypy/pull/20695))

Performance Improvements

- Replace `NamedTuple` with faster regular classes in hot paths (Shantanu, PR [21326](https://github.com/python/mypy/pull/21326))
- Avoid calling best-match suggestions unless the message is shown (Ivan Levkivskyi, PR [21307](https://github.com/python/mypy/pull/21307))
- Order cases in native parser based on AST node frequency (Jukka Lehtosalo, PR [21219](https://github.com/python/mypy/pull/21219))

Stubtest Improvements

- Basic support for unpack kwargs (Shantanu, PR [21024](https://github.com/python/mypy/pull/21024))
- Fix false positive for properties with a deleter (Pranav Manglik, PR [21259](https://github.com/python/mypy/pull/21259))

Documentation Updates

- Rename &quot;value restriction&quot; to &quot;value-constrained type variable&quot; (Leo Ji, PR [21112](https://github.com/python/mypy/pull/21112))
- Clarify that invariant-by-default applies to legacy `TypeVar` syntax (Leo Ji, PR [21108](https://github.com/python/mypy/pull/21108))

Improvements to the Native Parser

The new native parser is still experimental.

- Make new parser consistent with the old one (Ivan Levkivskyi, PR [21377](https://github.com/python/mypy/pull/21377))
- Support `--package-root` with the native parser (Ivan Levkivskyi, PR [21321](https://github.com/python/mypy/pull/21321))
- Improve call expressions in type annotations with the native parser (Jukka Lehtosalo, PR [21300](https://github.com/python/mypy/pull/21300))
- Depend on `ast-serialize` by default (Jukka Lehtosalo, PR [21297](https://github.com/python/mypy/pull/21297))

Other Notable Fixes and Improvements

- Fix narrowing for `AbstractSet` and `Mapping` (Shantanu, PR [21352](https://github.com/python/mypy/pull/21352))
- Preserve gradual guarantee when narrowing `Any` union via equality (Shantanu, PR [21368](https://github.com/python/mypy/pull/21368))
- Make type variable upper bound narrowing symmetric (Ivan Levkivskyi, PR [21350](https://github.com/python/mypy/pull/21350))
- Behave consistently when type-checking a stub package directly (Ivan Levkivskyi, PR [21330](https://github.com/python/mypy/pull/21330))
- Add support for `Final[...]` in dataclasses (Ivan Levkivskyi, PR [21334](https://github.com/python/mypy/pull/21334))
- Narrow more sequence parents (Shantanu, PR [21327](https://github.com/python/mypy/pull/21327))
- Better narrowing for enums and other types with known equality (Shantanu, PR [21281](https://github.com/python/mypy/pull/21281))
- Fix pathspec error (Ivan Levkivskyi, PR [21296](https://github.com/python/mypy/pull/21296))
- Use sharding for the SQLite cache (Jukka Lehtosalo, PR [21292](https://github.com/python/mypy/pull/21292))
- Limit type inference context fallback to the walrus operator only (Ivan Levkivskyi, PR [21294](https://github.com/python/mypy/pull/21294))
- Support `.git/info/exclude` for `--exclude-gitignore` (RogerJinIS, PR [21286](https://github.com/python/mypy/pull/21286))
- Let `--allow-redefinition` widen a global in a function with `None` initialization (Jukka Lehtosalo, PR [21285](https://github.com/python/mypy/pull/21285))
- Delete Python 2 extra (Shantanu, PR [18374](https://github.com/python/mypy/pull/18374))
- No longer narrow final globals in functions (Ivan Levkivskyi, PR [21241](https://github.com/python/mypy/pull/21241))
- Narrow unions containing `Any` in conditional branches (Shantanu, PR [21231](https://github.com/python/mypy/pull/21231))
- Propagate narrowing within chained comparisons (Shantanu, PR [21160](https://github.com/python/mypy/pull/21160))
- Add proper lazy deserialization (Ivan Levkivskyi, PR [21198](https://github.com/python/mypy/pull/21198))
- Add `install_types` to options affecting cache (Brian Schubert, PR [21070](https://github.com/python/mypy/pull/21070))
- Narrow `Any` in conditional type checks (Shantanu, PR [21167](https://github.com/python/mypy/pull/21167))
- Fix exception handler target location in new parser (Ivan Levkivskyi, PR [21185](https://github.com/python/mypy/pull/21185))
- Improve traceback display (Shantanu, PR [21155](https://github.com/python/mypy/pull/21155))
- Include two more files in the sdist: `CREDITS` and the typeshed `README` (Michael R. Crusoe, PR [21131](https://github.com/python/mypy/pull/21131))

Typeshed Updates

Please see [git log](https://github.com/python/typeshed/commits/main?after=c5e47faeda2cf9d233f91bc1dc95814b0cc7ccba+0&amp;branch=main&amp;path=stdlib) for full list of standard library typeshed stub changes.

Acknowledgements

Thanks to all mypy contributors who contributed to this release:
- Brian Schubert
- Ethan Sarp
- Ivan Levkivskyi
- Jukka Lehtosalo
- Kevin Kannammalil
- Leo Ji
- Marc Mueller
- Michael R. Crusoe
- Piotr Sawicki
- Pranav Manglik
- RogerJinIS
- Shantanu
- Vaggelis Danias
- wyattscarpenter
- Yosof Badr

I’d also like to thank my employer, Dropbox, for supporting mypy development.

1.20.2

- Use WAL with SQLite cache and fix close (Shantanu, PR [21154](https://github.com/python/mypy/pull/21154))
- Adjust SQLite journal mode (Ivan Levkivskyi, PR [21217](https://github.com/python/mypy/pull/21217))
- Correctly aggregate narrowing information on parent expressions (Shantanu, PR [21206](https://github.com/python/mypy/pull/21206))
- Fix regression related to generic callables (Shantanu, PR [21208](https://github.com/python/mypy/pull/21208))
- Fix regression by avoiding widening types in some contexts (Shantanu, PR [21242](https://github.com/python/mypy/pull/21242))
- Fix slicing in non-strict optional mode (Shantanu, PR [21282](https://github.com/python/mypy/pull/21282))
- mypyc: Fix match statement semantics for &quot;or&quot; pattern (Shantanu, PR [21156](https://github.com/python/mypy/pull/21156))
- mypyc: Fix issue with module dunder attributes (Piotr Sawicki, PR [21275](https://github.com/python/mypy/pull/21275))
- Initial support for Python 3.15.0a8 (Marc Mueller, PR [21255](https://github.com/python/mypy/pull/21255))

Acknowledgements

Thanks to all mypy contributors who contributed to this release:
- A5rocks
- Aaron Wieczorek
- Adam Turner
- Ali Hamdan
- asce
- BobTheBuidler
- Brent Westbrook
- Brian Schubert
- bzoracler
- Chris Burroughs
- Christoph Tyralla
- Colin Watson
- Donghoon Nam
- E. M. Bray
- Emma Smith
- Ethan Sarp
- George Ogden
- getzze
- grayjk
- Gregor Riepl
- Ivan Levkivskyi
- James Hilliard
- James Le Cuirot
- Jeremy Nimmer
- Joren Hammudoglu
- Kai (Kazuya Ito)
- kaushal trivedi
- Kevin Kannammalil
- Lukas Geiger
- Łukasz Langa
- Marc Mueller
- Michael R. Crusoe
- michaelm-openai
- Neil Schemenauer
- Piotr Sawicki
- Randolf Scholz
- Roberto Fernández Iglesias
- Saul Shanabrook
- Shantanu Jain
- Sjoerd Job Postmus
- sobolevn
- Stanislav Terliakov
- Steven Pitman
- Vaggelis Danias
- Vikash Kumar
- wyattscarpenter

I’d also like to thank my employer, Dropbox, for supporting mypy development.

1.20.1

- Always disable sync in SQLite cache (Ivan Levkivskyi, PR [21184](https://github.com/python/mypy/pull/21184))
- Temporarily skip few base64 tests (Ivan Levkivskyi, PR [21193](https://github.com/python/mypy/pull/21193))
- Revert `dict.__or__` typeshed change (Ivan Levkivskyi, PR [21186](https://github.com/python/mypy/pull/21186))
- Fix narrowing for match case with variadic tuples (Shantanu, PR [21192](https://github.com/python/mypy/pull/21192))
- Avoid narrowing `type[T]` in type calls (Shantanu, PR [21174](https://github.com/python/mypy/pull/21174))
- Fix regression for catching empty tuple in except (Shantanu, PR [21153](https://github.com/python/mypy/pull/21153))
- Fix reachability for frozenset and dict view narrowing (Shantanu, PR [21151](https://github.com/python/mypy/pull/21151))
- Fix narrowing with chained comparison (Shantanu, PR [21150](https://github.com/python/mypy/pull/21150))
- Avoid narrowing to unreachable at module level (Shantanu, PR [21144](https://github.com/python/mypy/pull/21144))
- Allow dangerous identity comparisons to `Any` typed variables (Shantanu, PR [21142](https://github.com/python/mypy/pull/21142))
- `--warn-unused-config` should not be a strict flag (Ivan Levkivskyi, PR [21139](https://github.com/python/mypy/pull/21139))

1.20

We’ve just uploaded mypy 1.20.0 to the Python Package Index ([PyPI](https://pypi.org/project/mypy/)).
Mypy is a static type checker for Python. This release includes new features, performance
improvements and bug fixes. You can install it as follows:

 python3 -m pip install -U mypy

You can read the full documentation for this release on [Read the Docs](http://mypy.readthedocs.io).

Planned Changes to Defaults and Flags in Mypy 2.0

As a reminder, we are planning to enable `--local-partial-types` by default in mypy 2.0, which
will likely be the next feature release. This will often require at least minor code changes. This
option is implicitly enabled by mypy daemon, so this makes the behavior of daemon and non-daemon
modes consistent.

Note that this release improves the compatibility of `--local-partial-types` significantly to
make the switch easier (see below for more).

This can also be configured in a mypy configuration file (use `False` to disable):


local_partial_types = True


For more information, refer to the
[documentation](https://mypy.readthedocs.io/en/stable/command_line.html#cmdoption-mypy-local-partial-types).

We will also enable `--strict-bytes` by default in mypy 2.0. This usually requires at most
minor code changes to adopt. For more information, refer to the
[documentation](https://mypy.readthedocs.io/en/stable/command_line.html#cmdoption-mypy-strict-bytes).

Finally, `--allow-redefinition-new` will be renamed to `--allow-redefinition`. If you want
to continue using the older `--allow-redefinition` semantics which are less flexible (e.g.
limited support for conditional redefinitions), you can switch to `--allow-redefinition-old`,
which is currently supported as an alias to the legacy `--allow-redefinition` behavior.
To use `--allow-redefinition` in the upcoming mypy 2.0, you can&#x27;t use `--no-local-partial-types`.
For more information, refer to the
[documentation](https://mypy.readthedocs.io/en/stable/command_line.html#cmdoption-mypy-allow-redefinition-new).

Better Type Narrowing

Mypy&#x27;s implementation of narrowing has been substantially reworked. Mypy will now narrow more
aggressively, more consistently, and more correctly. In particular, you are likely to notice new
narrowing behavior in equality expressions (`==`), containment expressions (`in`),
match statements, and additional expressions providing type guards.

Note that mypy (and other Python type checkers) do not model the potential for various non-local
operations to invalidate narrowing assumptions. This means mypy may conclude that some of your code
is [unreachable](https://mypy.readthedocs.io/en/stable/common_issues.html#unreachable-code) and
avoid further checking of it. The `--warn-unreachable` flag is useful for highlighting these cases.
To reset narrowing, you can insert dummy reassignments, for instance `var = var` will reset
all narrowing of `var.attr`.

Future work includes better narrowing on initial assignments, more narrowing to `Literal` types,
and better checking of unreachable code.

Contributed by Shantanu Jain.

- Rework narrowing logic for equality and identity (Shantanu, PR [20492](https://github.com/python/mypy/pull/20492))
- Refactor equality and identity narrowing for clarity (Shantanu, PR [20595](https://github.com/python/mypy/pull/20595))
- Treat NotImplemented as a singleton type (Shantanu, PR [20601](https://github.com/python/mypy/pull/20601))
- Improve narrowing logic for Enum int and str subclasses (Shantanu, PR [20609](https://github.com/python/mypy/pull/20609))
- Narrow types based on collection containment (Shantanu, PR [20602](https://github.com/python/mypy/pull/20602))
- Refactor and improve narrowing for type(x) == t checks (Shantanu, PR [20634](https://github.com/python/mypy/pull/20634))
- Narrow for type expr comparisons to type exprs (Shantanu, PR [20639](https://github.com/python/mypy/pull/20639))
- Narrowing for comparisons against `x.__class__` (Shantanu, PR [20642](https://github.com/python/mypy/pull/20642))
- Better narrowing with custom equality (Shantanu, PR [20643](https://github.com/python/mypy/pull/20643))
- Use a single pass for core narrowing logic, add comments (Shantanu, PR [20659](https://github.com/python/mypy/pull/20659))
- Narrowing for final type objects (Shantanu, PR [20661](https://github.com/python/mypy/pull/20661))
- Avoid narrowing type[T] (Shantanu, PR [20662](https://github.com/python/mypy/pull/20662))
- Avoid widening to Any for checks like `type(x) is type(y: Any)` (Shantanu, PR [20663](https://github.com/python/mypy/pull/20663))
- Preserve some lost narrowing, cleanup (Shantanu, PR [20674](https://github.com/python/mypy/pull/20674))
- Fix narrowing related code for types with overloaded `__new__` (Shantanu, PR [20676](https://github.com/python/mypy/pull/20676))
- Fix isinstance with unions of tuples (Shantanu, PR [20677](https://github.com/python/mypy/pull/20677))
- Fix regression to chained containment (Shantanu, PR [20688](https://github.com/python/mypy/pull/20688))
- Improve else handling with custom equality (Shantanu, PR [20692](https://github.com/python/mypy/pull/20692))
- Better model runtime in isinstance and type checks (Shantanu, PR [20675](https://github.com/python/mypy/pull/20675))
- Use --warn-unreachable and --strict-equality in more tests (Shantanu, PR [20707](https://github.com/python/mypy/pull/20707))
- Model exact narrowing with type(x) checks (Shantanu, PR [20703](https://github.com/python/mypy/pull/20703))
- Short term fix for bytes narrowing (Shantanu, PR [20704](https://github.com/python/mypy/pull/20704))
- Preserve narrowing in unreachable code (Shantanu, PR [20710](https://github.com/python/mypy/pull/20710))
- Fix bug when narrowing union containing custom eq against custom eq (Shantanu, PR [20754](https://github.com/python/mypy/pull/20754))
- Fix narrowing for unions (Shantanu, PR [20728](https://github.com/python/mypy/pull/20728))
- Unsoundly narrow away from None with custom eq (Shantanu, PR [20756](https://github.com/python/mypy/pull/20756))
- Improve narrowing with numeric types (Shantanu, PR [20727](https://github.com/python/mypy/pull/20727))
- Fix narrowing with final type objects (Shantanu, PR [20743](https://github.com/python/mypy/pull/20743))
- Further improve match statement narrowing against unions (Shantanu, PR [20744](https://github.com/python/mypy/pull/20744))
- Avoid narrowing to NewType (Shantanu, PR [20766](https://github.com/python/mypy/pull/20766))
- Better match narrowing for irrefutable sequence patterns (Shantanu, PR [20782](https://github.com/python/mypy/pull/20782))
- Remove prohibit_none_typevar_overlap (Shantanu, PR [20864](https://github.com/python/mypy/pull/20864))
- Fix match statement narrowing reachability for tuples (Shantanu, PR [20896](https://github.com/python/mypy/pull/20896))
- Better handling of generics when narrowing (Shantanu, PR [20863](https://github.com/python/mypy/pull/20863))
- Better match narrowing for type objects (Shantanu, PR [20872](https://github.com/python/mypy/pull/20872))
- Narrow Callable generic return types (Shantanu, PR [20868](https://github.com/python/mypy/pull/20868))
- Better match narrowing for unions of type objects (Shantanu, PR [20905](https://github.com/python/mypy/pull/20905))
- Improve reachability in narrowing logic (Shantanu, PR [20660](https://github.com/python/mypy/pull/20660))
- Better match narrowing for irrefutable mapping patterns (Shantanu, PR [20906](https://github.com/python/mypy/pull/20906))
- Fix match statement semantic reachability (Shantanu, PR [20968](https://github.com/python/mypy/pull/20968))
- Add some additional narrowing test cases (Shantanu, PR [20598](https://github.com/python/mypy/pull/20598))
- Move tests to check-narrowing , improve them slightly (Shantanu, PR [20637](https://github.com/python/mypy/pull/20637))
- Add more tests for narrowing logic (Shantanu, PR [20672](https://github.com/python/mypy/pull/20672))
- More testing related improvements and updates (Shantanu, PR [20709](https://github.com/python/mypy/pull/20709))
- Add --warn-unreachable to more tests (Shantanu, PR [20977](https://github.com/python/mypy/pull/20977))

Drop Support for Python 3.9

Mypy no longer supports running with Python 3.9, which has reached end of life.
When running mypy with Python 3.10+, it is still possible to type check code
that needs to support Python 3.9 with the `--python-version 3.9` argument.
Support for this will be dropped in the first half of 2026!

Contributed by Marc Mueller (PR [20156](https://github.com/python/mypy/pull/20156)).

Mypyc Accelerated Mypy Wheels for ARM Windows and Free Threading

For best performance, mypy can be compiled to C extension modules using mypyc. This makes
mypy 3-5x faster than when interpreted with pure Python. We now build and upload mypyc
accelerated mypy wheels for `win_arm64` and `cp314t-...` to PyPI, making it easy for Windows
users on ARM and those using the free theading builds for Python 3.14 to realise this speedup
-- just `pip install` the latest mypy.

Contributed by Marc Mueller
(PR [mypy_mypyc-wheels106](https://github.com/mypyc/mypy_mypyc-wheels/pull/106),
PR [mypy_mypyc-wheels110](https://github.com/mypyc/mypy_mypyc-wheels/pull/110)).

Improved Compatibility for Local Partial Types

Compatibility between mypy&#x27;s default behavior and the `--local-partial-types` flag
is now improved. This improves compatibility between mypy daemon and non-daemon modes,
since the mypy daemon requires local partial types to be enabled.

In particular, code like this now behaves consistently independent of
whether local partial types are enabled or not:

python
x = None

def foo() -&gt; None:
 global x
 x = 1

The inferred type of &#x27;x&#x27; is always &#x27;int | None&#x27;.


Also, we are planning to turn local partial types on by default in mypy 2.0 (to be
released soon), and this makes the change much less disruptive. Explicitly disabling local
partial types will continue to be supported, but the support will likely be
deprecated and removed eventually, as the legacy behavior is hard to support together with
some important changes we are working on, in addition to being incompatible with the mypy
daemon.

This feature was contributed by Ivan Levkivskyi (PR [20938](https://github.com/python/mypy/pull/20938)).

Python 3.14 T-String Support (PEP 750)

Mypy now supports t-strings that were introduced in Python 3.14.

- Add support for Python 3.14 t-strings (PEP 750) (Neil Schemenauer and Brian Schubert, PR [20850](https://github.com/python/mypy/pull/20850))
- Add implicit module dependency if using t-string (Jukka Lehtosalo, PR [20900](https://github.com/python/mypy/pull/20900))

Experimental New Parser

If you install mypy using `pip install mypy[native-parser]` and run mypy with
`--native-parser`, you can experiment with a new Python parser. It is based on
the Ruff parser, and it&#x27;s more efficient than the default parser. It will also enable
access to all Python syntax independent of which Python version you use to run mypy.
The new parser is still not feature-complete and has known issues.

Related changes:

- Add work-in-progress implementation of a new Python parser (Jukka Lehtosalo, PR [20856](https://github.com/python/mypy/pull/20856))
- Skip redundant analysis pass when using the native parser (Ivan Levkivskyi, PR [21015](https://github.com/python/mypy/pull/21015))
- Add t-string support to native parser (Ivan Levkivskyi, PR [21007](https://github.com/python/mypy/pull/21007))
- Handle hex bigint literals in native parser (Ivan Levkivskyi, PR [20988](https://github.com/python/mypy/pull/20988))
- Pass all relevant options to native parser (Ivan Levkivskyi, PR [20984](https://github.com/python/mypy/pull/20984))
- Support `no_type_check` with native parser (Ivan Levkivskyi, PR [20959](https://github.com/python/mypy/pull/20959))
- Fix error code handling in native parser (Ivan Levkivskyi, PR [20952](https://github.com/python/mypy/pull/20952))
- Add `ast-serialize` as an optional dependency (Ivan Levkivskyi, PR [21028](https://github.com/python/mypy/pull/21028))
- Use `native-parser` instead of `native-parse` for optional dependency (Jukka Lehtosalo, PR [21115](https://github.com/python/mypy/pull/21115))

Performance Improvements

Mypy now uses a binary cache format (fixed-format cache) by default to speed up incremental
checking. You can still use `--no-fixed-format-cache` to use the legacy JSON cache format,
but we will remove the JSON cache format in a future release. Mypy includes a tool to convert
individual fixed-format cache files (.ff) to the JSON format to make it possible to inspect
cache contents:

python
python -m mypy.exportjson &lt;path&gt; ...


If the SQLite cache is enabled, you will first need to convert the SQLite cache into
individual files using the [`misc/convert-cache.py`](https://github.com/python/mypy/blob/master/misc/convert-cache.py)
tool available in the mypy GitHub repository. You can also disable the SQLite
cache using `--no-sqlite-cache`.

The SQLite cache (`--sqlite-cache`) is now enabled by default. It improves mypy
performance significantly in certain environments where slow file system operations
used to be a bottleneck.

List of all performance improvements (for mypyc improvements there is a separate section below):

- Flip fixed-format cache to on by default (Ivan Levkivskyi, PR [20758](https://github.com/python/mypy/pull/20758))
- Enable `--sqlite-cache` by default (Shantanu, PR [21041](https://github.com/python/mypy/pull/21041))
- Save work on emitting ignored diagnostics (Shantanu, PR [20621](https://github.com/python/mypy/pull/20621))
- Skip logging and stats collection calls if they are no-ops (Jukka Lehtosalo, PR [20839](https://github.com/python/mypy/pull/20839))
- Speed up large incremental builds by optimizing internal state construction (Jukka Lehtosalo, PR [20838](https://github.com/python/mypy/pull/20838))
- Speed up suppressed dependencies options processing (Jukka Lehtosalo, PR [20806](https://github.com/python/mypy/pull/20806))
- Avoid path operations that need syscalls (Jukka Lehtosalo, PR [20802](https://github.com/python/mypy/pull/20802))
- Use faster algorithm for topological sort (Jukka Lehtosalo, PR [20790](https://github.com/python/mypy/pull/20790))
- Replace old topological sort (Jukka Lehtosalo, PR [20805](https://github.com/python/mypy/pull/20805))
- Fix quadratic performance in dependency graph loading for incremental builds (Jukka Lehtosalo, PR [20786](https://github.com/python/mypy/pull/20786))
- Micro-optimize transitive dependency hash calculation (Jukka Lehtosalo, PR [20798](https://github.com/python/mypy/pull/20798))
- Speed up options snapshot calculation (Jukka Lehtosalo, PR [20797](https://github.com/python/mypy/pull/20797))
- Micro-optimize read buffering, metastore `abspath`, path joining (Shantanu, PR [20810](https://github.com/python/mypy/pull/20810))
- Speed up type comparisons and hashing for literal types (Shantanu, PR [20423](https://github.com/python/mypy/pull/20423))
- Optimize overloaded signatures check (asce, PR [20378](https://github.com/python/mypy/pull/20378))
- Avoid unnecessary work when checking deferred functions (Ivan Levkivskyi, PR [20860](https://github.com/python/mypy/pull/20860))
- Improve `--allow-redefinition-new` performance for code with loops (Ivan Levkivskyi, PR [20862](https://github.com/python/mypy/pull/20862))
- Avoid `setattr`/`getattr` with fixed format cache (Ivan Levkivskyi, PR [20826](https://github.com/python/mypy/pull/20826))

Improvements to Allowing Redefinitions

Mypy now allows significantly more flexible variable redefinitions when using `--allow-redefinition-new`.
In particular, function parameters can now be redefined with a different type:

python
mypy: allow-redefinition-new, local-partial-types

def process(items: list[str]) -&gt; None:
  Reassign parameter to a completely different type.
  Without --allow-redefinition-new, this is a type error because
  list[list[str]] is not compatible with list[str].
 items = [item.split() for item in items]
 ...


In mypy 2.0, we will update `--allow-redefinition` to mean `--allow-redefinition-new`.
This release adds `--allow-redefinition-old` as an alias of `--allow-redefinition`, which
can be used to continue using the old redefinition behavior in mypy 2.0 and later.

List of changes:

- Add `--allow-redefinition-old` as an alias of `--allow-redefinition` (Ivan Levkivskyi, PR [20764](https://github.com/python/mypy/pull/20764))
- Allow redefinitions for function arguments (Ivan Levkivskyi, PR [20853](https://github.com/python/mypy/pull/20853))
- Fix regression on redefinition in deferred loop (Ivan Levkivskyi, PR [20879](https://github.com/python/mypy/pull/20879))
- Fix loop convergence with redefinitions (Ivan Levkivskyi, PR [20865](https://github.com/python/mypy/pull/20865))
- Make sure new redefinition semantics only apply to inferred variables (Ivan Levkivskyi, PR [20909](https://github.com/python/mypy/pull/20909))
- Fix union edge case in function argument redefinition (Ivan Levkivskyi, PR [20908](https://github.com/python/mypy/pull/20908))
- Show an error when old and new redefinition are enabled in a file (Ivan Levkivskyi, PR [20920](https://github.com/python/mypy/pull/20920))
- `--allow-redefinition-new` is no longer experimental (Jukka Lehtosalo, PR [21110](https://github.com/python/mypy/pull/21110))
- Fix type inference for nested union types (Ivan Levkivskyi, PR [20912](https://github.com/python/mypy/pull/20912))
- Fix type inference regression for multiple variables in loops (Ivan Levkivskyi, PR [20892](https://github.com/python/mypy/pull/20892))
- Improve type inference for empty collections in conditional contexts (Ivan Levkivskyi, PR [20851](https://github.com/python/mypy/pull/20851))

Incremental Checking Improvements

This release includes multiple fixes to incremental type checking:

- Invalidate cache when `--enable-incomplete-feature` changes (kaushal trivedi, PR [20849](https://github.com/python/mypy/pull/20849))
- Add back support for `warn_unused_configs` (Ivan Levkivskyi, PR [20801](https://github.com/python/mypy/pull/20801))
- Recover from corrupted fixed-format cache meta file (Jukka Lehtosalo, PR [20780](https://github.com/python/mypy/pull/20780))
- Distinguish not found versus skipped modules (Ivan Levkivskyi, PR [20812](https://github.com/python/mypy/pull/20812))
- Fix undetected submodule deletion on warm run (Ivan Levkivskyi, PR [20784](https://github.com/python/mypy/pull/20784))
- Fix staleness on changed follow-imports options (Ivan Levkivskyi, PR [20773](https://github.com/python/mypy/pull/20773))
- Verify indirect dependencies reachable on incremental run (Ivan Levkivskyi, PR [20735](https://github.com/python/mypy/pull/20735))
- Fix indirect dependencies for protocols (Ivan Levkivskyi, PR [20752](https://github.com/python/mypy/pull/20752))
- Show error locations in other modules on warm runs (Ivan Levkivskyi, PR [20635](https://github.com/python/mypy/pull/20635))
- Don&#x27;t read errors from cache on silent import (Sjoerd Job Postmus, PR [20509](https://github.com/python/mypy/pull/20509))
- More robust fix for re-export of `__all__` (Ivan Levkivskyi, PR [20487](https://github.com/python/mypy/pull/20487))

Fixes to Crashes

- Fix crash on partially typed namespace package (Ivan Levkivskyi, PR [20742](https://github.com/python/mypy/pull/20742))
- Fix internal error caused by the generic type alias with an unpacked list (Kai (Kazuya Ito), PR [20689](https://github.com/python/mypy/pull/20689))
- Fix crash when missing format character (Shantanu, PR [20524](https://github.com/python/mypy/pull/20524))
- Fix crash when passing literal values as type arguments to variadic generics (Aaron Wieczorek, PR [20543](https://github.com/python/mypy/pull/20543))
- Fix crash on circular star import in incremental mode (Ivan Levkivskyi, PR [20511](https://github.com/python/mypy/pull/20511))
- Fix crash with tuple unpack inside TypeVar default (Marc Mueller, PR [20456](https://github.com/python/mypy/pull/20456))
- Fix crash on typevar with forward reference used in other module (Ivan Levkivskyi, PR [20334](https://github.com/python/mypy/pull/20334))
- Fix crash on star import of redefinition (Ivan Levkivskyi, PR [20333](https://github.com/python/mypy/pull/20333))
- Fix crash involving Unpack-ed `TypeVarTuple` (Shantanu, PR [20323](https://github.com/python/mypy/pull/20323))
- Fix crashes caused by type variable defaults in-place modifications (Stanislav Terliakov, PR [20139](https://github.com/python/mypy/pull/20139))
- Fix crash when calling `len()` with no arguments (Jukka Lehtosalo, PR [20774](https://github.com/python/mypy/pull/20774))
- Fix crash when checking `async for` inside nested comprehensions (A5rocks, PR [20540](https://github.com/python/mypy/pull/20540))
- Fix `ParamSpec` related crash (Stanislav Terliakov, PR [20119](https://github.com/python/mypy/pull/20119))

Mypyc: Faster Imports on macOS

Imports in native (compiled) modules that target other native modules that are compiled
together are now significantly faster on macOS, especially on the first run after a compiled
package has been installed. This also speeds up the first mypy run after installation/update
on macOS.

This was contributed by Jukka Lehtosalo (PR [21101](https://github.com/python/mypy/pull/21101)).

librt: Mypyc Standard Library

Mypyc now has a dedicated standard library, `librt`, to provide basic features that are optimized
for compiled code. They are faster than corresponding Python stdlib functionality. There is no
plan to replace the Python stdlib, though. We&#x27;ll only include a carefully selected set of features
that help with common performance bottlenecks in compiled code.

Currently, we provide `librt.base64` that has optimized SIMD (Single Instruction, Multiple
Data) base64 encoding and decoding functions. In future mypyc releases we are planning to
add efficient data structures, string/bytes utilities, and more.

Use `python3 -m pip install librt` to make `librt` available to compiled modules. Compiled
modules don&#x27;t require `librt` unless they explicitly import `librt`. If you install mypy, you
will also get a compatible version of `librt` as a dependency. We will keep `librt` backward
compatible, so you should always be able to update to a newer version of the library.

Related changes:

- Add minimal, experimental `librt.base64` module (Jukka Lehtosalo, PR [20226](https://github.com/python/mypy/pull/20226))
- Use faster base64 encode implementation in `librt.base64` (Jukka Lehtosalo, PR [20237](https://github.com/python/mypy/pull/20237))
- Add efficient `librt.base64.b64decode` (Jukka Lehtosalo, PR [20263](https://github.com/python/mypy/pull/20263))
- Enable SIMD for `librt.base64` on x86-64 (Jukka Lehtosalo, PR [20244](https://github.com/python/mypy/pull/20244))
- Add primitive for `librt.base64.b64decode` (Jukka Lehtosalo, PR [20272](https://github.com/python/mypy/pull/20272))
- Add `urlsafe_b64encode` and `urlsafe_b64decode` to `librt.base64` (Jukka Lehtosalo, PR [20274](https://github.com/python/mypy/pull/20274))
- Make `librt.base64` non-experimental (Ivan Levkivskyi, PR [20783](https://github.com/python/mypy/pull/20783))
- Support pyodide for Python 3.12 (Michael R. Crusoe, PR [20342](https://github.com/python/mypy/pull/20342))
- Support pyodide via the NEON intrinsics (Michael R. Crusoe, PR [20316](https://github.com/python/mypy/pull/20316))
- Fix `librt` compilation on platforms with OpenMP (Ivan Levkivskyi, PR [20583](https://github.com/python/mypy/pull/20583))
- Fix cross-compiling `librt` by enabling x86_64 optimizations with pragmas (James Le Cuirot, PR [20815](https://github.com/python/mypy/pull/20815))
- Use existing SIMD CPU dispatch by customizing build flags (Michael R. Crusoe, PR [20253](https://github.com/python/mypy/pull/20253))
- Document `librt` and `librt.base64` (Jukka Lehtosalo, PR [21114](https://github.com/python/mypy/pull/21114))

Mypyc: Acyclic Classes

Mypyc now supports defining acyclic native classes that don&#x27;t participate in the tracing
garbage collection:

python
from mypy_extensions import mypyc_attr

mypyc_attr(acyclic=True)
class Item:
 def __init__(self, key: str, value: str) -&gt; None:
     self.key = key
     self.value = value


Allocating and freeing instances of acyclic classes is faster than regular native class
instances, and they use less memory, but if they participate in reference cycles, there
may be memory leaks.

This was contributed by Jukka Lehtosalo (PR [20795](https://github.com/python/mypy/p

pyup-bot added 12 commits May 25, 2026 16:48

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pyup-bot mentioned this pull request May 25, 2026

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pyup-bot commented May 25, 2026

Update fonttools from 4.62.1 to 4.63.0.

4.63.0

Update lxml from 6.1.0 to 6.1.1.

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Update orjson from 3.11.7 to 3.11.9.

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Update black from 26.3.1 to 26.5.1.

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Update click from 8.3.1 to 8.4.1.

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Update coverage from 7.13.5 to 7.14.0.

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Update librt from 0.8.1 to 0.11.0.

Update mypy from 1.19.1 to 2.1.0.

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