Allow URL constraints to apply to requirements with extras

news/12018.bugfix.rst

@@ -0,0 +1 @@
+Allow URL constraints to apply to requirements with extras.

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

@@ -376,16 +376,28 @@ def _iter_candidates_from_constraints(
         This creates "fake" InstallRequirement objects that are basically clones
         of what "should" be the template, but with original_link set to link.
         """
+        extras: frozenset[str] = frozenset()
+        base_identifier = identifier
+        with contextlib.suppress(InvalidRequirement):
+            parsed_requirement = get_requirement(identifier)
+            if parsed_requirement.name != identifier:
+                base_identifier = canonicalize_name(parsed_requirement.name)
+                extras = frozenset(parsed_requirement.extras)
+
         for link in constraint.links:
             self._fail_if_link_is_unsupported_wheel(link)
-            candidate = self._make_base_candidate_from_link(
+            base_candidate = self._make_base_candidate_from_link(
                 link,
                 template=install_req_from_link_and_ireq(link, template),
-                name=canonicalize_name(identifier),
+                name=canonicalize_name(base_identifier),
                 version=None,
             )
-            if candidate:
-                yield candidate
+            if base_candidate is None:
+                continue
+            if extras:
+                yield self._make_extras_candidate(base_candidate, extras)
+            else:
+                yield base_candidate
 
     def find_candidates(
         self,

tests/functional/test_install_reqs.py

@@ -680,6 +680,35 @@ def test_install_with_extras_from_install(script: PipTestEnvironment) -> None:
     result.did_create(script.site_packages / "singlemodule.py")
 
 
+def test_install_with_extras_and_url_constraint(
+    script: PipTestEnvironment,
+) -> None:
+    """Regression test for https://github.com/pypa/pip/issues/12018.
+
+    A URL constraint for the base package plus a requirement that asks for
+    the same package with extras used to trigger an AssertionError in
+    LinkCandidate (``'name[extra]' != 'name' for wheel``).
+    """
+    create_basic_wheel_for_package(
+        script,
+        name="LocalExtras",
+        version="0.0.1",
+        extras={"baz": ["singlemodule"]},
+    )
+    wheel_path = next(script.scratch_path.glob("LocalExtras-0.0.1-*.whl"))
+    script.scratch_path.joinpath("constraints.txt").write_text(
+        f"LocalExtras @ {wheel_path.as_uri()}"
+    )
+    result = script.pip_install_local(
+        "--find-links",
+        script.scratch_path,
+        "-c",
+        script.scratch_path / "constraints.txt",
+        "LocalExtras[baz]",
+    )
+    result.did_create(script.site_packages / "singlemodule.py")
+
+
 def test_install_with_extras_joined(
     script: PipTestEnvironment, data: TestData, resolver_variant: ResolverVariant
 ) -> None: