Try less hacky way

Author: mroeschke

.github/workflows/package-checks.yml

@@ -38,12 +38,12 @@ jobs:
         with:
           python-version: '3.8'
 
-      # Can take a significant amount of time while this should only check that
-      # the extras are installed
-      - name: Disable building ext_modules
-        run: |
-          sed -i '/ext_modules=/d' setup.py
-        shell: bash -el {0}
+#      # Can take a significant amount of time while this should only check that
+#      # the extras are installed
+#      - name: Disable building ext_modules
+#        run: |
+#          sed -i '/ext_modules=/d' setup.py
+#        shell: bash -el {0}
 
       - name: Install required dependencies
         run: |
@@ -52,5 +52,5 @@ jobs:
 
       - name: Pip install with extra
         run: |
-          python -m pip install -e .[${{ matrix.extra }}] --no-build-isolation
+          python -m pip install -e .[${{ matrix.extra }}] --no-build-isolation --install-option="no-extensions"
         shell: bash -el {0}

setup.py

@@ -407,6 +407,10 @@ def maybe_cythonize(extensions, *args, **kwargs):
         # See https://github.com/cython/cython/issues/1495
         return extensions
 
+    elif "no-extensions" in sys.argv:
+        # For pip install extras CI job in .github/workflows/package-checks.yml
+        return []
+
     elif not _CYTHON_INSTALLED:
         # GH#28836 raise a helfpul error message
         if _CYTHON_VERSION: