Add ast-serialize as an optional dependency (#21028)

A skipped test in `check-overloads.test` seems to be caused by a recent
change in `ast_serialize`. FWIW it looks like a bug in the old parser?
Leaving the test up to @JukkaL

Author: ilevkivskyi

.github/workflows/test.yml

@@ -106,20 +106,17 @@ jobs:
           os: ubuntu-24.04-arm
           toxenv: py
           tox_extra_args: "-n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
-          dev_ast_serialize: true
         - name: Parallel tests with py314-ubuntu, mypyc-compiled
           python: '3.14'
           os: ubuntu-24.04-arm
           toxenv: py
           tox_extra_args: "-n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
           test_mypyc: true
-          dev_ast_serialize: true
         - name: Parallel tests with py314-windows-64, interpreted
           python: '3.14'
           os: windows-latest
           toxenv: py
           tox_extra_args: "-n 2 --mypy-num-workers=2 mypy/test/testcheck.py -k 'incremental or modules or classes'"
-          dev_ast_serialize: true
 
         - name: Type check our own code (py310-ubuntu)
           python: '3.10'
@@ -142,7 +139,6 @@ jobs:
     timeout-minutes: 60
     env:
       TOX_SKIP_MISSING_INTERPRETERS: False
-      VIRTUALENV_SYSTEM_SITE_PACKAGES: ${{ matrix.dev_ast_serialize && 1 || 0 }}
       # Rich (pip) -- Disable color for windows + pytest
       FORCE_COLOR: ${{ !(startsWith(matrix.os, 'windows-') && startsWith(matrix.toxenv, 'py')) && 1 || 0 }}
       # Tox
@@ -217,11 +213,6 @@ jobs:
         pip install -r test-requirements.txt
         CC=clang MYPYC_OPT_LEVEL=0 MYPY_USE_MYPYC=1 pip install -e .
 
-    # To speed-up process until ast_serialize is on PyPI.
-    - name: Install pinned ast-serialize
-      if: ${{ matrix.dev_ast_serialize }}
-      run: pip install ast-serialize@git+https://github.com/mypyc/ast_serialize.git@052c5bfa3b2a5bf07c0b163ccbe2c5ccbfae9ac5
-
     - name: Setup tox environment
       run: |
         tox run -e ${{ matrix.toxenv }} --notest

docs/source/common_issues.rst

@@ -228,11 +228,12 @@ make cold mypy runs several times faster.
 
 Furthermore: as of `mypy 1.13 <https://mypy-lang.blogspot.com/2024/10/mypy-113-released.html>`_,
 mypy allows use of the orjson library for handling the cache instead of the stdlib json, for
-improved performance. You can ensure the presence of orjson using the faster-cache extra:
+improved performance. You can ensure the presence of orjson using the ``faster-cache`` extra:
 
     python3 -m pip install -U mypy[faster-cache]
 
-Mypy may depend on orjson by default in the future.
+Mypy may depend on orjson by default in the future. To use faster, native parser, use the
+``native-parse`` extra. Native parser will be default in near future.
 
 Types of empty collections
 --------------------------

pyproject.toml

@@ -64,6 +64,7 @@ python2 = []
 reports = ["lxml"]
 install-types = ["pip"]
 faster-cache = ["orjson"]
+native-parse = ["ast-serialize>=0.1.1,<1.0.0"]
 
 [project.urls]
 Homepage = "https://www.mypy-lang.org/"

test-data/unit/check-overloading.test

@@ -6165,7 +6165,7 @@ reveal_type(f3(A()))  # E: No overload variant of "f3" matches argument type "A"
     # N: Revealed type is "Any"
 reveal_type(f3(B()))  # N: Revealed type is "__main__.B"
 
-[case testOverloadIfSplitFunctionDef]
+[case testOverloadIfSplitFunctionDef_no_native_parse]
 # flags: --always-true True --always-false False
 from typing import overload
 

test-requirements.in

@@ -13,3 +13,4 @@ pytest-cov>=2.10.0
 setuptools>=77.0.3
 tomli>=1.1.0  # needed even on py311+ so the self check passes with --python-version 3.10
 pre_commit>=3.5.0
+ast-serialize>=0.1.1,<1.0.0

test-requirements.txt

@@ -4,6 +4,8 @@
 #
 #    pip-compile --allow-unsafe --output-file=test-requirements.txt --strip-extras test-requirements.in
 #
+ast-serialize==0.1.1
+    # via -r test-requirements.in
 attrs==25.4.0
     # via -r test-requirements.in
 cfgv==3.4.0