Upgrade resolvelib to 1.2.1

Author: notatallshaw

news/resolvelib.vendor.rst

@@ -0,0 +1 @@
+Upgrade resolvelib to 1.2.1

src/pip/_vendor/resolvelib/__init__.py

@@ -11,7 +11,7 @@
     "__version__",
 ]
 
-__version__ = "1.2.0"
+__version__ = "1.2.1"
 
 
 from .providers import AbstractProvider

src/pip/_vendor/resolvelib/resolvers/abstract.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import collections
-from typing import TYPE_CHECKING, Any, Generic, Iterable, Mapping, NamedTuple
+from typing import TYPE_CHECKING, Any, Generic, Iterable, NamedTuple
 
 from ..structs import CT, KT, RT, DirectedGraph
 
@@ -11,9 +11,9 @@
     from .criterion import Criterion
 
     class Result(NamedTuple, Generic[RT, CT, KT]):
-        mapping: Mapping[KT, CT]
+        mapping: dict[KT, CT]
         graph: DirectedGraph[KT | None]
-        criteria: Mapping[KT, Criterion[RT, CT]]
+        criteria: dict[KT, Criterion[RT, CT]]
 
 else:
     Result = collections.namedtuple("Result", ["mapping", "graph", "criteria"])

src/pip/_vendor/resolvelib/resolvers/resolution.py

@@ -384,6 +384,11 @@ def _backjump(self, causes: list[RequirementInformation[RT, CT]]) -> bool:
                 if not broken_state.mapping:
                     break
 
+                # Guard: We need at least two state to remain to both
+                # backtrack and push a new state
+                if len(self._states) <= 1:
+                    raise ResolutionImpossible(causes)
+
             incompatibilities_from_broken = [
                 (k, list(v.incompatibilities)) for k, v in broken_state.criteria.items()
             ]

src/pip/_vendor/vendor.txt

@@ -11,7 +11,7 @@ requests==2.32.5
     urllib3==1.26.20
 rich==14.2.0
     pygments==2.19.2
-resolvelib==1.2.0
+resolvelib==1.2.1
 setuptools==70.3.0
 tomli==2.2.1
 tomli-w==1.2.0