Test and build wheels on Python 3.15

.github/workflows/python-package.yml

@@ -79,6 +79,35 @@ jobs:
         # a missing confluent_kafka -- actually run.
         kafka-driver: ['aiokafka']
         include:
+          # Python 3.15.  `allow-prereleases` below resolves this to whatever
+          # pre-release the runner image publishes -- 3.15.0rc1 at the time of
+          # writing, and 3.15.0 final once it ships, with no change needed
+          # here.  Same shape as a stable row: Cython on and off, plus a
+          # confluent leg.
+          #
+          # Advisory (`experimental: true` -> `continue-on-error`) for two
+          # reasons.  The pre-release one is the same as everywhere else: rc2
+          # and final are still to come.  The specific one is that faust does
+          # not import at all on 3.15 until mode-streaming ships the fix for
+          # `typing._eval_type`, whose `type_params` argument became a required
+          # positional in 3.15 -- every faust Record model resolves its
+          # annotations through `mode.utils.objects.annotations`, so collection
+          # dies before the first test runs.  The fix is on mode's master; this
+          # leg goes green once a mode-streaming release carries it (bump the
+          # floor in requirements/requirements.txt then, and move these entries
+          # into the matrix above to make 3.15 required).
+          - python-version: '3.15'
+            use-cython: 'true'
+            experimental: true
+            kafka-driver: 'aiokafka'
+          - python-version: '3.15'
+            use-cython: 'false'
+            experimental: true
+            kafka-driver: 'aiokafka'
+          - python-version: '3.15'
+            use-cython: 'false'
+            experimental: true
+            kafka-driver: 'confluent'
           # confluent driver: broker-less unit tests over a pure-Python
           # wrapper, so one leg per Python version (Cython off) is enough.
           - python-version: '3.10'
@@ -111,6 +140,13 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
+          # Required by the 3.15 rows: a bare `3.15` matches stable releases
+          # only and fails with "Version 3.15 was not found in the local
+          # cache".  Safe for every other row -- it widens `3.X` to
+          # `~3.X.0-0`, and a pre-release only wins when no stable release
+          # satisfies the spec, so 3.10-3.14 still resolve to their newest
+          # stable patch.
+          allow-prereleases: true
           cache: pip
           # See the lint job: test.txt alone leaves the key unchanged when the
           # transitively-included pins move, and the confluent legs below
@@ -317,7 +353,15 @@ jobs:
         # cibuildwheel 2.21.3 predates CPython 3.14, so `build = "cp3*"`
         # stopped at cp313 and no 3.14 wheels were published (issue #715).
         # 4.x builds 3.14 by default and still supports cp310-cp313.
-        uses: pypa/cibuildwheel@v4.1.0
+        #
+        # 4.2.0 is the first pin that knows about CPython 3.15, and it builds
+        # cp315 by default -- no `CIBW_ENABLE: cpython-prerelease` needed,
+        # because cibuildwheel gates a Python behind that group only until its
+        # first release candidate (the ABI is frozen at rc1, so a wheel built
+        # against 3.15.0rc1 is forward-compatible with 3.15.0 final).  The
+        # `cp31?t-*` skip in pyproject.toml's [tool.cibuildwheel] keeps this
+        # to cp315, without cp315t, matching the other versions.
+        uses: pypa/cibuildwheel@v4.2.0
       - uses: actions/upload-artifact@v4
         with:
           name: cibw-wheels-${{ matrix.os }}

pyproject.toml

@@ -31,6 +31,7 @@ classifiers = [
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: 3.14",
+    "Programming Language :: Python :: 3.15",
     "Programming Language :: Python :: Implementation :: CPython",
     "Operating System :: POSIX",
     "Operating System :: POSIX :: Linux",

tox.ini

@@ -1,5 +1,8 @@
 [tox]
-envlist = 3.12,3.11,3.10,flake8,apicheck,configcheck,typecheck,docstyle,bandit,spell
+# Version envs mirror the CI matrix in
+# .github/workflows/python-package.yml.  3.15 is still a pre-release; tox
+# skips it unless a 3.15 interpreter is on PATH.
+envlist = 3.15,3.14,3.13,3.12,3.11,3.10,flake8,apicheck,configcheck,typecheck,docstyle,bandit,spell
 
 [testenv]
 deps=
@@ -16,10 +19,21 @@ sitepackages = False
 recreate = False
 commands = py.test --random-order --open-files -xvv --cov=faust tests/unit tests/functional tests/integration tests/meticulous/ tests/regression
 
+# One interpreter per version env, and a single pinned one for the checks.
+# The previous form repeated the whole check list (flake8, typecheck, ...) on
+# all three lines, so every one of those factors matched all three at once and
+# tox resolved `base_python` to nothing -- leaving the checks on whatever
+# interpreter happened to be running tox.  That is silently version-dependent
+# for `typecheck`.  They now pin to 3.12, the PYTHON_LATEST the CI workflow
+# runs its lint job on.
 basepython =
-    3.12,flake8,apicheck,linkcheck,configcheck,typecheck,docstyle,bandit,spell: python3.12
-    3.11,flake8,apicheck,linkcheck,configcheck,typecheck,docstyle,bandit,spell: python3.11
-    3.10,flake8,apicheck,linkcheck,configcheck,typecheck,docstyle,bandit,spell: python3.10
+    3.15: python3.15
+    3.14: python3.14
+    3.13: python3.13
+    3.12: python3.12
+    3.11: python3.11
+    3.10: python3.10
+    flake8,apicheck,linkcheck,configcheck,typecheck,docstyle,bandit,spell: python3.12
 
 [testenv:apicheck]
 setenv =