Optimize upgrade of already-satisfied pinned requirement

Example: after installing six 1.12.0, `pip install -Uv six==1.12.0` now returns immediately, instead of going to the index to check for a version that can’t possibly be considered better. This optimization is most significant when upgrading via a requirements file with many pinned versions and some non-pinned versions. Signed-off-by: Anders Kaseorg <[email protected]>
pypa · Oct 5, 2019 · d4191c3 · d4191c3
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diff --git a/news/7132.feature b/news/7132.feature
@@ -0,0 +1 @@
+Skip reaching out to the package index, if a pinned version is already satisfied.
diff --git a/src/pip/_internal/legacy_resolve.py b/src/pip/_internal/legacy_resolve.py
@@ -267,6 +267,10 @@ def _check_skip_installed(self, req_to_install):
  # requirements we have to pull the tree down and inspect to assess
  # the version #, so it's handled way down.
  if not req_to_install.link:
+ if req_to_install.is_pinned:
+ # No need to check the index for a better version.
+ return 'pinned at installed version'
+
  try:
  self.finder.find_requirement(req_to_install, upgrade=True)
  except BestVersionAlreadyInstalled: