Problem: `TypeError: dist must be a Distribution instance`

Solution: workaround pip _distutils_hack

.github/workflows/scripts-setuptools-head.yml

@@ -27,7 +27,6 @@ jobs:
       env:
         PACKAGE: ${{matrix.package}}
         PYTHON_VERSION: ${{matrix.python-version}}
-        SETUPTOOLS_USE_DISTUTILS: stdlib
       run: |
         sandbox/bin/buildout -v -c .github/workflows/scripts-${PYTHON_VERSION}.cfg annotate buildout
         sandbox/bin/buildout -c .github/workflows/scripts-${PYTHON_VERSION}.cfg

.github/workflows/scripts.yml

@@ -25,7 +25,6 @@ jobs:
       env:
         PACKAGE: ${{matrix.package}}
         PYTHON_VERSION: ${{matrix.python-version}}
-        SETUPTOOLS_USE_DISTUTILS: stdlib
       run: |
         sandbox/bin/buildout -v -c .github/workflows/scripts-${PYTHON_VERSION}.cfg annotate buildout
         sandbox/bin/buildout -c .github/workflows/scripts-${PYTHON_VERSION}.cfg

news/600.bugfix

+Fix `TypeError: dist must be a Distribution instance` due to issue between
+`setuptools` and `pip`.

src/zc/buildout/__init__.py

@@ -13,8 +13,25 @@
 ##############################################################################
 """Buildout package
 """
+# do not change the import order
+# deleting the spec_for_pip hack needs to be done before importing pip
+# see https://github.com/pypa/pip/issues/8761 to understand
+# the reason for the hack.
+# I think it is reasonable to assume we will not run into the race.
+import setuptools
+
+try:
+    from _distutils_hack import DistutilsMetaFinder
+    if hasattr(DistutilsMetaFinder, 'spec_for_pip'):
+        del DistutilsMetaFinder.spec_for_pip
+except ImportError:
+    pass
+
+import pip  # NOQA
+
+
 import sys
-import zc.buildout.patches # NOQA
+import zc.buildout.patches  # NOQA
 
 
 WINDOWS = sys.platform.startswith('win')