Add _contextvars as config-c-only

Author: zanieb

cpython-unix/extension-modules.yml

@@ -88,6 +88,9 @@ _collections:
 _contextvars:
   sources:
     - _contextvarsmodule.c
+  config-c-only-conditional:
+    - config-c-only: true
+      minimum-python-version: "3.14"
 
 _crypt:
   maximum-python-version: "3.12"

pythonbuild/cpython.py

@@ -286,6 +286,18 @@ def derive_setup_local(
         if info.get("config-c-only"):
             config_c_only_wanted.add(name)
 
+        for entry in info.get("config-c-only-conditional", []):
+            python_min_match_setup = meets_python_minimum_version(
+                python_version, entry.get("minimum-python-version", "1.0")
+            )
+            python_max_match_setup = meets_python_maximum_version(
+                python_version, entry.get("maximum-python-version", "100.0")
+            )
+            if entry.get("config-c-only", False) and (
+                python_min_match_setup and python_max_match_setup
+            ):
+                config_c_only_wanted.add(name)
+
     # Parse more files in the distribution for their metadata.
 
     with tarfile.open(str(cpython_source_archive)) as tf: