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Bug 1861061: change internal priority to low for async/deferred scripts with fetchpriority=auto and to high for module-scripts and scripts from head. r=smaug

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For web-compatibility; match Chromium's behavior.

Differential Revision: https://phabricator.services.mozilla.com/D196954
This commit is contained in:
Mirko Brodesser
2024-01-02 14:12:50 +00:00
parent 43ea78fedd
commit baff4c93ad
3 changed files with 92 additions and 34 deletions
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39
dom/script/ScriptLoader.cpp
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@@ -731,34 +731,49 @@ void AdjustPriorityForNonLinkPreloadScripts(nsIChannel* aChannel,
do_QueryInterface(aChannel)) {
LOG(("Is not <link rel=[module]preload"));
const RequestPriority fetchPriority = aRequest->FetchPriority();
// The spec defines the priority to be set in an implementation defined
// manner (<https://fetch.spec.whatwg.org/#concept-fetch>, step 15 and
// <https://html.spec.whatwg.org/#concept-script-fetch-options-fetch-priority>).
// For web-compatibility, the fetch priority mapping from
// <https://web.dev/articles/fetch-priority#browser_priority_and_fetchpriority>
// is taken.
const Maybe<int32_t> supportsPriorityValue = [&]() -> Maybe<int32_t> {
// <testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests-data.js>
// provides more context for the priority mapping.
const int32_t supportsPriorityValue = [&]() {
switch (fetchPriority) {
case RequestPriority::Auto:
return Nothing{};
case RequestPriority::Auto: {
if (aRequest->IsModuleRequest()) {
return nsISupportsPriority::PRIORITY_HIGH;
}
const ScriptLoadContext* scriptLoadContext =
aRequest->GetScriptLoadContext();
if (scriptLoadContext->IsAsyncScript() ||
scriptLoadContext->IsDeferredScript()) {
return nsISupportsPriority::PRIORITY_LOW;
}
if (scriptLoadContext->mScriptFromHead) {
return nsISupportsPriority::PRIORITY_HIGH;
}
return nsISupportsPriority::PRIORITY_NORMAL;
}
case RequestPriority::Low: {
return Some(nsISupportsPriority::PRIORITY_LOW);
return nsISupportsPriority::PRIORITY_LOW;
}
case RequestPriority::High: {
return Some(nsISupportsPriority::PRIORITY_HIGH);
return nsISupportsPriority::PRIORITY_HIGH;
}
default: {
MOZ_ASSERT_UNREACHABLE();
return Nothing{};
return nsISupportsPriority::PRIORITY_NORMAL;
}
}
}();
if (supportsPriorityValue) {
LogPriorityMapping(ScriptLoader::gScriptLoaderLog,
ToFetchPriority(fetchPriority),
*supportsPriorityValue);
supportsPriority->SetPriority(*supportsPriorityValue);
ToFetchPriority(fetchPriority), supportsPriorityValue);
supportsPriority->SetPriority(supportsPriorityValue);
}
}
}