Add Cython to CI

.github/workflows/ci.yml

@@ -204,6 +204,40 @@ jobs:
           name: Alpine
           flags: Alpine,3.12
 
+  Cython:
+    name: "Cython"
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python: ['3.8', '3.12']
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup python
+        uses: actions/setup-python@v5
+        with:
+            python-version: '${{ matrix.python }}'
+            cache: pip
+        # setuptools is needed to get distutils on 3.12, which cythonize requires
+      - name: install trio and setuptools
+        run: python -m pip install --upgrade pip . setuptools
+
+      - name: install cython<3
+        run: python -m pip install "cython<3"
+      - name: compile pyx file
+        run: cythonize -i tests/cython/test_cython.pyx
+      - name: import & run module
+        run: python -c 'import tests.cython.test_cython'
+
+      - name: install cython>=3
+        run: python -m pip install "cython>=3"
+      - name: compile pyx file
+        # different cython version should trigger a re-compile, but --force just in case
+        run: cythonize --inplace --force tests/cython/test_cython.pyx
+      - name: import & run module
+        run: python -c 'import tests.cython.test_cython'
+
   # https://github.com/marketplace/actions/alls-green#why
   check:  # This job does nothing and is only used for the branch protection
 
@@ -214,6 +248,7 @@ jobs:
       - Ubuntu
       - macOS
       - Alpine
+      - Cython
 
     runs-on: ubuntu-latest
 

src/trio/_core/_run.py

@@ -1767,6 +1767,7 @@ def spawn_impl(
             except AttributeError:
                 name = repr(name)
 
+        # very old Cython versions (<0.29.24) has the attribute, but with a value of None
         if getattr(coro, "cr_frame", None) is None:
             # This async function is implemented in C or Cython
             async def python_wrapper(orig_coro: Awaitable[RetT]) -> RetT:

tests/cython/test_cython.pyx

@@ -0,0 +1,22 @@
+# cython: language_level=3
+import trio
+
+# the output of the prints are not currently checked, we only check
+# if the program can be compiled and doesn't crash when run.
+
+# The content of the program can easily be extended if there's other behaviour
+# that might be likely to be problematic for cython.
+async def foo() -> None:
+    print('.')
+
+async def trio_main() -> None:
+    print('hello...')
+    await trio.sleep(1)
+    print(' world !')
+
+    async with trio.open_nursery() as nursery:
+        nursery.start_soon(foo)
+        nursery.start_soon(foo)
+        nursery.start_soon(foo)
+
+trio.run(trio_main)