Sort applicable candidates before computing best candidate (#7332)

Author: pradyunsg

docs/html/development/architecture/package-finding.rst

@@ -187,12 +187,11 @@ user, and other user preferences, etc.
 
 Specifically, the class has a ``get_applicable_candidates()`` method.
 This accepts the ``InstallationCandidate`` objects resulting from the links
-accepted by the ``LinkEvaluator`` class's ``evaluate_link()`` method, and
-it further filters them to a list of "applicable" candidates.
+accepted by the ``LinkEvaluator`` class's ``evaluate_link()`` method, filters
+them to a list of "applicable" candidates and orders them by preference.
 
 The ``CandidateEvaluator`` class also has a ``sort_best_candidate()`` method
-that orders the applicable candidates by preference, and then returns the
-best (i.e. most preferred).
+that returns the best (i.e. most preferred) candidate.
 
 Finally, the class has a ``compute_best_candidate()`` method that calls
 ``get_applicable_candidates()`` followed by ``sort_best_candidate()``, and

src/pip/_internal/index/package_finder.py

@@ -474,12 +474,14 @@ def get_applicable_candidates(
             c for c in candidates if str(c.version) in versions
         ]
 
-        return filter_unallowed_hashes(
+        filtered_applicable_candidates = filter_unallowed_hashes(
             candidates=applicable_candidates,
             hashes=self._hashes,
             project_name=self._project_name,
         )
 
+        return sorted(filtered_applicable_candidates, key=self._sort_key)
+
     def _sort_key(self, candidate):
         # type: (InstallationCandidate) -> CandidateSortingKey
         """