Remove extras from user-supplied constraints in backtracking resolver

piptools/resolver.py

@@ -520,6 +520,8 @@ def resolve(self, max_rounds: int = 10) -> set[InstallRequirement]:
         ), get_build_tracker() as build_tracker, global_tempdir_manager(), indent_log():
             # Mark direct/primary/user_supplied packages
             for ireq in self.constraints:
+                if ireq.constraint:
+                    ireq.extras = set()  # pip does not support extras in constraints
                 ireq.user_supplied = True
 
             # Pass compiled requirements from `requirements.txt`
@@ -535,7 +537,7 @@ def resolve(self, max_rounds: int = 10) -> set[InstallRequirement]:
                     if not primary_ireq.specifier.contains(version, prereleases):
                         continue
 
-                ireq.extras = set()  # pip does not support extras in constraints
+                ireq.extras = set()
                 ireq.constraint = True
                 ireq.user_supplied = False
                 compatible_existing_constraints[key_from_ireq(ireq)] = ireq

tests/test_cli_compile.py

@@ -939,6 +939,29 @@ def test_upgrade_packages_version_option_and_upgrade_no_existing_file(pip_conf,
     assert "small-fake-b==0.1" in out.stderr
 
 
+def test_upgrade_package_with_extra(pip_conf, make_package, runner):
+    """
+    piptools ignores extras on --upgrade-package/-P items if already constrained.
+    """
+    package_with_extra = make_package(
+        "package_with_extra",
+        extras_require={
+            "extra": ["small-fake-a==0.1"],
+        },
+    )
+
+    with open("requirements.in", "w") as req_in:
+        req_in.write(f"{package_with_extra}[extra]")
+
+    out = runner.invoke(
+        cli, ["--no-annotate", "--upgrade-package", "package_with_extra[extra]"]
+    )
+
+    assert out.exit_code == 0
+    assert "package_with_extra" in out.stderr
+    assert "small-fake-a==" in out.stderr
+
+
 def test_quiet_option(pip_conf, runner):
     with open("requirements.in", "w") as req_in:
         req_in.write("small-fake-a")