From 8bf159f4c777e22fc3e07ae89af73503cad64107 Mon Sep 17 00:00:00 2001
From: Tzu-ping Chung <uranusjr@gmail.com>
Date: Wed, 9 Dec 2020 11:27:51 +0800
Subject: [PATCH 1/2] Intentionally delay resolving setuptools

---
 src/pip/_internal/resolution/resolvelib/provider.py | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/pip/_internal/resolution/resolvelib/provider.py b/src/pip/_internal/resolution/resolvelib/provider.py
index 3883135f12b..40a641a2a4d 100644
--- a/src/pip/_internal/resolution/resolvelib/provider.py
+++ b/src/pip/_internal/resolution/resolvelib/provider.py
@@ -117,7 +117,18 @@ def _get_restrictive_rating(requirements):
         restrictive = _get_restrictive_rating(req for req, _ in information)
         transitive = all(parent is not None for _, parent in information)
         key = next(iter(candidates)).name if candidates else ""
-        return (restrictive, transitive, key)
+
+        # HACK: Setuptools have a very long and solid backward compatibility
+        # track record, and extremely few projects would request a narrow,
+        # non-recent version range of it since that would break a lot things.
+        # (Most projects specify it only to request for an installer feature,
+        # which does not work, but that's another topic.) Intentionally
+        # delaying Setuptools helps reduce branches the resolver has to check.
+        # This serves as a temporary fix for issues like "apache-airlfow[all]"
+        # while we work on "proper" branch pruning techniques.
+        delay_this = (key == "setuptools")
+
+        return (delay_this, restrictive, transitive, key)
 
     def find_matches(self, requirements):
         # type: (Sequence[Requirement]) -> Iterable[Candidate]

From 52523832481d33237acb9f03a2154500d2b63ad5 Mon Sep 17 00:00:00 2001
From: Tzu-ping Chung <uranusjr@gmail.com>
Date: Wed, 9 Dec 2020 18:42:17 +0800
Subject: [PATCH 2/2] News entry for setuptools priority hack

---
 news/9249.feature.rst | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 news/9249.feature.rst

diff --git a/news/9249.feature.rst b/news/9249.feature.rst
new file mode 100644
index 00000000000..1c56b39ef5d
--- /dev/null
+++ b/news/9249.feature.rst
@@ -0,0 +1 @@
+Add a mechanism to delay resolving certain packages, and use it for setuptools.