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 +939,56 @@ 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(runner, make_package, make_sdist, tmpdir):
+    """
+    piptools ignores extras on --upgrade-package/-P items if already constrained.
+    """
+    test_package_1 = make_package(
+        "test_package_1", version="0.1", extras_require={"more": "test_package_2"}
+    )
+    test_package_2 = make_package(
+        "test_package_2",
+        version="0.1",
+    )
+    dists_dir = tmpdir / "dists"
+    for pkg in (test_package_1, test_package_2):
+        make_sdist(pkg, dists_dir)
+
+    # Constrain our requirement with an extra
+    with open("requirements.in", "w") as req_in:
+        req_in.write("test-package-1[more]")
+
+    # Run update on test-package-1[more] -- this should be equivalent
+    # to running an update on test-package-1
+    out = runner.invoke(
+        cli,
+        [
+            "--output-file",
+            "-",
+            "--quiet",
+            "--find-links",
+            str(dists_dir),
+            "--no-annotate",
+            "--no-header",
+            "--no-emit-options",
+            "--no-build-isolation",
+            "--upgrade-package",
+            "test-package-1[more]",
+        ],
+    )
+
+    assert out.exit_code == 0, out
+    assert (
+        dedent(
+            """\
+            test-package-1[more]==0.1
+            test-package-2==0.1
+            """
+        )
+        == out.stdout
+    )
+
+
 def test_quiet_option(pip_conf, runner):
     with open("requirements.in", "w") as req_in:
         req_in.write("small-fake-a")