(joe) move the cache warming to the factory

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

@@ -46,6 +46,7 @@
 from pip._internal.resolution.base import InstallRequirementProvider
 from pip._internal.utils.compatibility_tags import get_supported
 from pip._internal.utils.hashes import Hashes
+from pip._internal.utils.parallel import LACK_SEM_OPEN, map_multithread
 from pip._internal.utils.virtualenv import running_under_virtualenv
 
 from .base import Candidate, CandidateVersion, Constraint, Requirement
@@ -344,6 +345,21 @@ def _iter_candidates_from_constraints(
             if candidate:
                 yield candidate
 
+    def pre_find_all(self, project_names: Iterator[str]) -> None:
+        if LACK_SEM_OPEN:
+            return
+        if not hasattr(self._finder.find_all_candidates, "cache_info"):
+            return
+
+        def _maybe_find_candidates(project_name: str) -> None:
+            try:
+                self._finder.find_all_candidates(project_name)
+            except AttributeError:
+                pass
+
+        for _ in map_multithread(_maybe_find_candidates, project_names):
+            pass
+
     def find_candidates(
         self,
         identifier: str,

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

@@ -21,7 +21,6 @@
 )
 from pip._internal.utils.deprecation import deprecated
 from pip._internal.utils.filetypes import is_archive_file
-from pip._internal.utils.parallel import LACK_SEM_OPEN, map_multithread
 
 from .base import Candidate, Requirement
 from .factory import Factory
@@ -90,17 +89,7 @@ def resolve(
             reporter,
         )
 
-        if LACK_SEM_OPEN is False:
-
-            def _maybe_find_candidates(req: Requirement) -> None:
-                ident = provider.identify(req)
-                try:
-                    self.factory._finder.find_all_candidates(ident)
-                except AttributeError:
-                    pass
-
-            for _ in map_multithread(_maybe_find_candidates, collected.requirements):
-                pass
+        self.factory.pre_find_all(provider.identify(r) for r in collected.requirements)
 
         try:
             try_to_avoid_resolution_too_deep = 2000000