fix(wpt): preserve explicit fixture cache controls

moli-benchmark/moli_benchmark/wpt_cross/server.py

@@ -3077,7 +3077,7 @@ def _make_handler(
                 self.send_header(name, value)
             if auto_content_length and not _headers_include(header_block, "Content-Length"):
                 self.send_header("Content-Length", str(len(body)))
-            if cache_control is not None:
+            if cache_control is not None and not _headers_include(header_block, "Cache-Control"):
                 self.send_header("Cache-Control", cache_control)
             self.end_headers()
             if emit_body:

moli-benchmark/tests/test_wpt_fixture_cache_control.py

@@ -0,0 +1,36 @@
+import tempfile
+import unittest
+from pathlib import Path
+from urllib.parse import urlencode
+from urllib.request import Request, urlopen
+
+from moli_benchmark.wpt_cross.server import WptFixtureServer
+
+
+class WptFixtureCacheControlTests(unittest.TestCase):
+    def test_explicit_cache_control_precedes_fixture_default(self) -> None:
+        with tempfile.TemporaryDirectory() as root:
+            root_path = Path(root)
+            (root_path / "resources").mkdir()
+            (root_path / "resources/testharness.js").write_text("// testharness")
+            (root_path / "module.json").write_text('{"value": 1}')
+            sidecar = root_path / "module.json.headers"
+            with WptFixtureServer(root_path) as server:
+                for header, pipe, expected in (
+                    (None, "", ["no-store"]),
+                    ("max-age=600", "", ["max-age=600"]),
+                    ("", "", [""]),
+                    (None, "header(Cache-Control,max-age=30)", ["max-age=30"]),
+                    (None, "header(cache-control,public)", ["public"]),
+                ):
+                    if header is None:
+                        sidecar.unlink(missing_ok=True)
+                    else:
+                        sidecar.write_text("cAcHe-CoNtRoL: " + header + "\n")
+                    for method in ("GET", "HEAD"):
+                        with self.subTest(header=header, pipe=pipe, method=method):
+                            url = server.base_url + "/module.json?" + urlencode({"pipe": pipe})
+                            with urlopen(Request(url, method=method), timeout=2) as response:
+                                self.assertEqual(response.status, 200)
+                                self.assertEqual(response.headers.get_all("Cache-Control"), expected)
+                                self.assertEqual(response.read(), b"" if method == "HEAD" else b'{"value": 1}')