Fix Direct Lookup in PipProvider.get_preference

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

@@ -14,6 +14,8 @@
 
 from pip._vendor.resolvelib.providers import AbstractProvider
 
+from pip._internal.resolution.resolvelib.requirements import ExplicitRequirement
+
 from .base import Candidate, Constraint, Requirement
 from .candidates import REQUIRES_PYTHON_IDENTIFIER
 from .factory import Factory
@@ -146,15 +148,15 @@ def get_preference(
             lookups = (r.get_candidate_lookup() for r, _ in information[identifier])
             candidate, ireqs = zip(*lookups)
         else:
-            candidate, ireqs = None, ()
+            candidate, ireqs = (None,), ()
 
         operators = [
             specifier.operator
             for specifier_set in (ireq.specifier for ireq in ireqs if ireq)
             for specifier in specifier_set
         ]
 
-        direct = candidate is not None
+        direct = any(candidate)
         pinned = any(op[:2] == "==" for op in operators)
         unfree = bool(operators)