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fix(early-hints): early hints don't need to be sync inside a FetchEve… #1323

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Merged
TartanLlama merged 1 commit into from
Feb 24, 2026
+115 −5
Merged

fix(early-hints): early hints don't need to be sync inside a FetchEve… #1323

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61 changes: 61 additions & 0 deletions integration-tests/js-compute/fixtures/app/src/early-hints.js
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Original file line number Diff line number Diff line change
Expand Up @@ -11,15 +11,76 @@ routes.set('/early-hints/manual-response', (event) => {
event.respondWith(new Response('ok'));
});

routes.set('/early-hints/manual-response-late', (event) => {
event.respondWith(new Response('ok'));
assertThrows(() => {
event.respondWith(
new Response(null, {
status: 103,
headers: { link: '</style.css>; rel=preload; as=style' },
}),
);
});
});

routes.set('/early-hints/manual-response-async', async (event) => {
await (async () => {
event.respondWith(
new Response(null, {
status: 103,
headers: { link: '</style.css>; rel=preload; as=style' },
}),
);
event.respondWith(new Response('ok'));
})();
});

routes.set('/early-hints/manual-response-late-async', async (event) => {
await (async () => {
event.respondWith(new Response('ok'));
assertThrows(() => {
event.respondWith(
new Response(null, {
status: 103,
headers: { link: '</style.css>; rel=preload; as=style' },
}),
);
});
})();
});

routes.set('/early-hints/send-early-hints', (event) => {
event.sendEarlyHints({ link: '</style.css>; rel=preload; as=style' });
event.respondWith(new Response('ok'));
});

routes.set('/early-hints/send-early-hints-late', (event) => {
event.respondWith(new Response('ok'));
assertThrows(() => {
event.sendEarlyHints({ link: '</style.css>; rel=preload; as=style' });
});
});

routes.set('/early-hints/send-early-hints-multiple-headers', (event) => {
event.sendEarlyHints([
['link', '</style.css>; rel=preload; as=style'],
['link', '</style2.css>; rel=preload; as=style'],
]);
event.respondWith(new Response('ok'));
});

routes.set('/early-hints/send-early-hints-async', async (event) => {
await (async () => {
event.sendEarlyHints({ link: '</style.css>; rel=preload; as=style' });
event.respondWith(new Response('ok'));
})();
});

routes.set('/early-hints/send-early-hints-late-async', async (event) => {
await (async () => {
event.respondWith(new Response('ok'));
assertThrows(() => {
event.sendEarlyHints({ link: '</style.css>; rel=preload; as=style' });
});
})();
});
54 changes: 54 additions & 0 deletions integration-tests/js-compute/fixtures/app/tests.json
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Original file line number Diff line number Diff line change
Expand Up @@ -3142,6 +3142,33 @@
}
}
},
"GET /early-hints/manual-response-late": {
"environments": ["compute"],
"downstream_response": {
"body": "ok",
"status": 200
}
},
"GET /early-hints/manual-response-async": {
"environments": ["compute"],
"downstream_response": {
"body": "ok",
"status": 200
},
"downstream_info": {
"status": 103,
"headers": {
"link": "</style.css>; rel=preload; as=style"
}
}
},
"GET /early-hints/manual-response-late-async": {
"environments": ["compute"],
"downstream_response": {
"body": "ok",
"status": 200
}
},
"GET /early-hints/send-early-hints": {
"environments": ["compute"],
"downstream_response": {
Expand All @@ -3155,6 +3182,13 @@
}
}
},
"GET /early-hints/send-early-hints-late": {
"environments": ["compute"],
"downstream_response": {
"body": "ok",
"status": 200
}
},
"GET /early-hints/send-early-hints-multiple-headers": {
"environments": ["compute"],
"downstream_response": {
Expand All @@ -3169,6 +3203,26 @@
]
}
},
"GET /early-hints/send-early-hints-async": {
"environments": ["compute"],
"downstream_response": {
"body": "ok",
"status": 200
},
"downstream_info": {
"status": 103,
"headers": {
"link": "</style.css>; rel=preload; as=style"
}
}
},
"GET /early-hints/send-early-hints-late-async": {
"environments": ["compute"],
"downstream_response": {
"body": "ok",
"status": 200
}
},
"GET /shielding/invalid-shield": {
"environments": ["compute"]
},
Expand Down
5 changes: 0 additions & 5 deletions runtime/fastly/builtins/fetch-event.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -908,11 +908,6 @@ bool FetchEvent::sendEarlyHints(JSContext *cx, unsigned argc, JS::Value *vp) {
METHOD_HEADER(1)
MOZ_RELEASE_ASSERT(state(self) == State::unhandled || state(self) == State::waitToRespond);

if (!is_dispatching(self)) {
JS_ReportErrorUTF8(cx, "FetchEvent#sendEarlyHints must be called synchronously from "
"within a FetchEvent handler");
return false;
}
if (state(self) != State::unhandled && state(self) != State::waitToRespond) {
JS_ReportErrorUTF8(
cx, "FetchEvent#sendEarlyHints can't be called after the main response has been sent");
Expand Down
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