Detect user-requested package names by preparing

This always prepares each explicit requirements when the resolver is
run, instead of when they are being resolved. But we always want to
prepare them anyway (an explicit requirement has only one candidate, so
it's either do or die), so this is not really a problem.

Author: uranusjr

news/9204.bugfix.rst

@@ -0,0 +1,2 @@
+New resolver: Detect an unnamed requirement is user-specified (by building its
+metadata for the project name) so it can be correctly ordered in the resolver.

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

@@ -473,16 +473,15 @@ def collect_root_requirements(self, root_ireqs):
                 else:
                     collected.constraints[name] = Constraint.from_ireq(ireq)
             else:
-                if ireq.user_supplied and ireq.name:
-                    canonical_name = canonicalize_name(ireq.name)
-                    if canonical_name not in collected.user_requested:
-                        collected.user_requested[canonical_name] = i
                 req = self._make_requirement_from_install_req(
                     ireq,
                     requested_extras=(),
                 )
-                if req is not None:
-                    collected.requirements.append(req)
+                if req is None:
+                    continue
+                if ireq.user_supplied and req.name not in collected.user_requested:
+                    collected.user_requested[req.name] = i
+                collected.requirements.append(req)
         return collected
 
     def make_requirement_from_candidate(self, candidate):