From 7c07fec3f02093bf048a1192473ab0736211e47e Mon Sep 17 00:00:00 2001
From: "Jason R. Coombs" <jaraco@jaraco.com>
Date: Fri, 4 Sep 2020 09:29:21 -0400
Subject: When pip is imported as part of a build, leave distutils patched.
 Fixes #2355.

---
 _distutils_hack/__init__.py | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to '_distutils_hack/__init__.py')

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()
 
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