# This is a combination of 14 commits.tree 962cf1d58cffa4bd5102aa4cc6…

…c1adaedb8c3cc0

parent 02b4f86
author Damian <[email protected]> 1633754869 -0400
committer Damian <[email protected]> 1633754892 -0400

# This is a combination of 13 commits.
# This is the 1st commit message:

Return a better error message if a `file:` URL is not found (pypa#10263)

Co-authored-by: Tzu-ping Chung <[email protected]>
Co-authored-by: Pradyun Gedam <[email protected]>
# This is the commit message #2:

Prefer failure causes when backtracking

# This is the commit message #3:

This fix is in the wrong PR confusing matters

# This is the commit message pypa#4:

Change name to backtrack_causes
Create is_backtrack_cause function

# This is the commit message pypa#5:

Fix newlines

# This is the commit message pypa#6:

Typo Fix in Comment

# This is the commit message pypa#7:

Fix lint errors

# This is the commit message pypa#8:

Add News Item

# This is the commit message pypa#9:

Newline

# This is the commit message pypa#10:

Better news.

# This is the commit message pypa#11:

Fix known depths

# This is the commit message pypa#12:

Fix known depths

# This is the commit message pypa#13:

Fix known depths

# This is the commit message pypa#14:

This fix is in the wrong PR confusing matters

news/10479.feature.rst

@@ -0,0 +1 @@
+New resolver: When backtracking prefer the dependencies which caused the most recent backtracking. In some cases this will significantly reduce the amount of backtracking required.

src/pip/_internal/resolution/resolvelib/provider.py

@@ -71,7 +71,8 @@ def get_preference(
         identifier: str,
         resolutions: Mapping[str, Candidate],
         candidates: Mapping[str, Iterator[Candidate]],
-        information: Mapping[str, Iterable["PreferenceInformation"]],
+        information: Mapping[str, Iterator["PreferenceInformation"]],
+        backtrack_causes: Sequence["RequirementInformation"],
     ) -> "Preference":
         """Produce a sort key for given requirement based on preference.
 
@@ -112,9 +113,9 @@ def get_preference(
                 for _, parent in information[identifier]
             )
             inferred_depth = min(d for d in parent_depths) + 1.0
+            self._known_depths[identifier] = inferred_depth
         else:
             inferred_depth = 1.0
-        self._known_depths[identifier] = inferred_depth
 
         requested_order = self._user_requested.get(identifier, math.inf)
 
@@ -132,11 +133,17 @@ def get_preference(
         # while we work on "proper" branch pruning techniques.
         delay_this = identifier == "setuptools"
 
+        # Prefer the causes of backtracking on the assumption that the problem
+        # resolving the dependency tree is related to the failures that caused
+        # the backtracking
+        backtrack_cause = self.is_backtrack_cause(identifier, backtrack_causes)
+
         return (
             not requires_python,
             delay_this,
             not direct,
             not pinned,
+            not backtrack_cause,
             inferred_depth,
             requested_order,
             not unfree,
@@ -195,3 +202,14 @@ def is_satisfied_by(self, requirement: Requirement, candidate: Candidate) -> boo
     def get_dependencies(self, candidate: Candidate) -> Sequence[Requirement]:
         with_requires = not self._ignore_dependencies
         return [r for r in candidate.iter_dependencies(with_requires) if r is not None]
+
+    @staticmethod
+    def is_backtrack_cause(
+        identifier: str, backtrack_causes: Sequence["RequirementInformation"]
+    ) -> bool:
+        for backtrack_cause in backtrack_causes:
+            if identifier == backtrack_cause.requirement.name:
+                return True
+            if backtrack_cause.parent and identifier == backtrack_cause.parent.name:
+                return True
+        return False