When pip is imported as part of a build, leave distutils patched. Fixes #2355.

1 files changed, 13 insertions, 0 deletions

diff --git a/_distutils_hack/__init__.py b/_distutils_hack/__init__.py
index 504c4ac0..c31edfed 100644
--- a/_distutils_hack/__init__.py
+++ b/_distutils_hack/__init__.py
@@ -92,9 +92,22 @@ class DistutilsMetaFinder:
         Ensure stdlib distutils when running under pip.
         See pypa/pip#8761 for rationale.
         """
+        if self.pip_imported_during_build():
+            return
         clear_distutils()
         self.spec_for_distutils = lambda: None
 
+    @staticmethod
+    def pip_imported_during_build():
+        """
+        Detect if pip is being imported in a build script. Ref #2355.
+        """
+        import traceback
+        return any(
+            frame.f_globals['__file__'].endswith('setup.py')
+            for frame, line in traceback.walk_stack(None)
+        )
+
 
 DISTUTILS_FINDER = DistutilsMetaFinder()