Implement wheel cache lookup in the new resolver

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

@@ -238,9 +238,21 @@ class LinkCandidate(_InstallRequirementBackedCandidate):
         version=None,  # type: Optional[_BaseVersion]
     ):
         # type: (...) -> None
+        cache_entry = factory.get_wheel_cache_entry(link, name)
+        if cache_entry is not None:
+            logger.debug("Using cached wheel link: %s", cache_entry.link)
+            link = cache_entry.link
+        ireq = make_install_req_from_link(link, parent)
+
+        # TODO: Is this logic setting original_link_is_in_wheel_cache correct?
+        if (cache_entry is not None and
+                cache_entry.persistent and
+                parent.link is parent.original_link):
+            ireq.original_link_is_in_wheel_cache = True
+
         super(LinkCandidate, self).__init__(
             link=link,
-            ireq=make_install_req_from_link(link, parent),
+            ireq=ireq,
             factory=factory,
             name=name,
             version=version,

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

@@ -8,6 +8,7 @@ from pip._internal.exceptions import (
     InstallationError,
     UnsupportedPythonVersion,
 )
+from pip._internal.utils.compatibility_tags import get_supported
 from pip._internal.utils.misc import (
     dist_in_site_packages,
     dist_in_usersite,
@@ -37,6 +38,7 @@ if MYPY_CHECK_RUNNING:
     from pip._vendor.pkg_resources import Distribution
     from pip._vendor.resolvelib import ResolutionImpossible
 
+    from pip._internal.cache import CacheEntry, WheelCache
     from pip._internal.index.package_finder import PackageFinder
     from pip._internal.models.link import Link
     from pip._internal.operations.prepare import RequirementPreparer
@@ -60,6 +62,7 @@ class Factory(object):
         finder,  # type: PackageFinder
         preparer,  # type: RequirementPreparer
         make_install_req,  # type: InstallRequirementProvider
+        wheel_cache,  # type: Optional[WheelCache]
         use_user_site,  # type: bool
         force_reinstall,  # type: bool
         ignore_installed,  # type: bool
@@ -70,6 +73,7 @@ class Factory(object):
 
         self.finder = finder
         self.preparer = preparer
+        self._wheel_cache = wheel_cache
         self._python_candidate = RequiresPythonCandidate(py_version_info)
         self._make_install_req_from_spec = make_install_req
         self._use_user_site = use_user_site
@@ -218,6 +222,24 @@ class Factory(object):
             return None
         return RequiresPythonRequirement(specifier, self._python_candidate)
 
+    def get_wheel_cache_entry(self, link, name):
+        # type: (Link, Optional[str]) -> Optional[CacheEntry]
+        """Look up the link in the wheel cache.
+
+        If ``preparer.require_hashes`` is True, don't use the wheel cache,
+        because cached wheels, always built locally, have different hashes
+        than the files downloaded from the index server and thus throw false
+        hash mismatches. Furthermore, cached wheels at present have
+        undeterministic contents due to file modification times.
+        """
+        if self._wheel_cache is None or self.preparer.require_hashes:
+            return None
+        return self._wheel_cache.get_cache_entry(
+            link=link,
+            package_name=name,
+            supported_tags=get_supported(),
+        )
+
     def should_reinstall(self, candidate):
         # type: (Candidate) -> bool
         # TODO: Are there more cases this needs to return True? Editable?

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

@@ -88,6 +88,7 @@ class Resolver(BaseResolver):
             finder=finder,
             preparer=preparer,
             make_install_req=make_install_req,
+            wheel_cache=wheel_cache,
             use_user_site=use_user_site,
             force_reinstall=force_reinstall,
             ignore_installed=ignore_installed,

tests/unit/resolution_resolvelib/conftest.py

@@ -52,6 +52,7 @@ def factory(finder, preparer):
         finder=finder,
         preparer=preparer,
         make_install_req=install_req_from_line,
+        wheel_cache=None,
         use_user_site=False,
         force_reinstall=False,
         ignore_installed=False,