Filter out build requirements that require an extra to be used

news/11112.bugfix.rst

@@ -0,0 +1 @@
+Properly filter out optional dependencies (i.e. extras) when checking build environment distributions.

src/pip/_internal/build_env.py

@@ -175,8 +175,10 @@ def check_requirements(
             )
             for req_str in reqs:
                 req = Requirement(req_str)
-                if req.marker is not None and not req.marker.evaluate():
-                    continue  # FIXME: Consider extras?
+                # We're explicitly evaluating with an empty extra value, since build
+                # environments are not provided any mechanism to select specific extras.
+                if req.marker is not None and not req.marker.evaluate({"extra": ""}):
+                    continue
                 dist = env.get_distribution(req.name)
                 if not dist:
                     missing.add(req_str)

tests/functional/test_build_env.py

@@ -178,6 +178,7 @@ def test_build_env_requirements_check(script: PipTestEnvironment) -> None:
             [
                 "bar==2.0; python_version < '3.0'",
                 "bar==3.0; python_version >= '3.0'",
+                "foo==4.0; extra == 'dev'",
             ],
         )
         assert r == (set(), set()), repr(r)