Setuptools needs work

[ngoldbaum]

If I patch brotlicffi like this:

diff --git a/setup.py b/setup.py
index e7176fe..77c55e2 100644
--- a/setup.py
+++ b/setup.py
@@ -93,12 +93,10 @@ setup(
     author_email="cory@lukasa.co.uk",

     setup_requires=[
-        "cffi>=1.0.0; python_version<'3.13'",
-        "cffi>=1.17.0; python_version>='3.13'",
+        "cffi @ git+https://github.com/python-cffi/cffi.git"
     ],
     install_requires=[
-        "cffi>=1.0.0; python_version<'3.13'",
-        "cffi>=1.17.0; python_version>='3.13'",
+        "cffi @ git+https://github.com/python-cffi/cffi.git"
     ],
     python_requires=">=3.8",
     cffi_modules=["src/brotlicffi/_build.py:ffi"],
diff --git a/src/brotlicffi/_build.py b/src/brotlicffi/_build.py
index 115be2e..afe5836 100644
--- a/src/brotlicffi/_build.py
+++ b/src/brotlicffi/_build.py
@@ -21,7 +21,8 @@ ffi.set_source(
        #include <brotli/encode.h>
     """,
     libraries=libraries,
-    include_dirs=["libbrotli/c", "libbrotli/c/include", "libbrotli/c/common"]
+    include_dirs=["libbrotli/c", "libbrotli/c/include", "libbrotli/c/common"],
+    define_macros=[("Py_LIMITED_API", "0x030f0000"), ('_Py_OPAQUE_PYOBJECT', '1')],
 )

 ffi.cdef("""

Then I'm able to build brotlicffi correctly on the GIL-enabled build. However, if I try with the free-threaded interpreter, I see errors like:

File "/private/var/folders/nk/yds4mlh97kg9qdq745g715rw0000gn/T/pip-build-env-3mhoegai/overlay/lib/python3.15t/site-packages/setuptools/command/bdist_wheel.py", line 285, in _validate_py_limited_api
          raise ValueError(
          ...<4 lines>...
          )
      ValueError: `py_limited_api='cp315'` not supported. `Py_LIMITED_API` is currently incompatible with `Py_GIL_DISABLED`. See https://github.com/python/cpython/issues/111506.

Which indicates to me that we need a fork of setuptools to work around this.

I can build brotlicffi on the free-threaded build if I haphazardly patch setuptools like so:

diff --git a/setuptools/command/bdist_wheel.py b/setuptools/command/bdist_wheel.py
index 3bdfa0b35..d2686469f 100644
--- a/setuptools/command/bdist_wheel.py
+++ b/setuptools/command/bdist_wheel.py
@@ -281,14 +281,6 @@ class bdist_wheel(Command):
         if not re.match(PY_LIMITED_API_PATTERN, self.py_limited_api):
             raise ValueError(f"py-limited-api must match '{PY_LIMITED_API_PATTERN}'")

-        if sysconfig.get_config_var("Py_GIL_DISABLED"):
-            raise ValueError(
-                f"`py_limited_api={self.py_limited_api!r}` not supported. "
-                "`Py_LIMITED_API` is currently incompatible with "
-                "`Py_GIL_DISABLED`. "
-                "See https://github.com/python/cpython/issues/111506."
-            )
-
     @property
     def wheel_dist_name(self) -> str:
         """Return distribution full name with - replaced with _"""
@@ -353,9 +345,6 @@ class bdist_wheel(Command):
             supported_tags = [
                 (t.interpreter, t.abi, plat_name) for t in tags.sys_tags()
             ]
-            assert tag in supported_tags, (
-                f"would build wheel with unsupported tag {tag}"
-            )
         return tag

     def run(self):

But I think deleting that assert is incorrect and instead we need to teach setuptools about the abi3.abi3t tag because the resulting wheel I get is tagged as abi3.cp315.

There's a comment in the setuptools tests in this repo that references pypa/setuptools#4810, which I think means the setuptools tests aren't actually testing anything?

Maybe using cffi would be a better way to test setuptools, since it seems to be easier to add C defines via CFFI's define_macros argument.

ping @kumaraditya303

[ngoldbaum]

#2 fixed the setuptools situation