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test_async_dead_await_fastpath.cjs
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test_async_dead_await_fastpath.cjs
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const now =
typeof performance !== 'undefined' && performance && typeof performance.now === 'function'
? () => performance.now()
: () => Date.now();
function median(values) {
const sorted = [...values].sort((a, b) => a - b);
const mid = sorted.length >> 1;
return sorted.length % 2 === 0
? (sorted[mid - 1] + sorted[mid]) / 2
: sorted[mid];
}
function formatMetric(label, result) {
console.log(
`${label}: median=${result.medianMs.toFixed(3)}ms ` +
`(${result.usPerOp.toFixed(3)}us/op, ${Math.round(result.opsPerSec)} ops/s)`
);
}
function yieldTick() {
return new Promise((resolve) => setTimeout(resolve, 0));
}
async function bench(label, iterations, fn, rounds = 5) {
for (let i = 0; i < 2; i++) {
await yieldTick();
for (let j = 0; j < Math.min(1000, iterations); j++) {
await fn();
}
}
const samples = [];
for (let round = 0; round < rounds; round++) {
await yieldTick();
const start = now();
for (let i = 0; i < iterations; i++) {
await fn();
}
samples.push(now() - start);
}
const medianMs = median(samples);
const opsPerSec = iterations / (medianMs / 1000);
const usPerOp = (medianMs * 1000) / iterations;
const result = { medianMs, opsPerSec, usPerOp, samples };
formatMetric(label, result);
return result;
}
function getColorEnabled() {
const { process, Deno } = globalThis;
const isNoColor =
typeof Deno?.noColor === 'boolean'
? Deno.noColor
: process !== void 0
? 'NO_COLOR' in process?.env
: false;
return !isNoColor;
}
async function getColorEnabledAsync() {
const { navigator } = globalThis;
const cfWorkers = 'cloudflare:workers';
const isNoColor =
navigator !== void 0 && navigator.userAgent === 'Cloudflare-Workers'
? await (async () => {
try {
return 'NO_COLOR' in ((await import(cfWorkers)).env ?? {});
} catch {
return false;
}
})()
: !getColorEnabled();
return !isNoColor;
}
async function asyncWrapSync() {
return !getColorEnabled();
}
async function navGuardOnly() {
const { navigator } = globalThis;
const isNoColor =
navigator !== void 0 && navigator.userAgent === 'Cloudflare-Workers'
? false
: !getColorEnabled();
return !isNoColor;
}
async function deadAwaitBranch() {
const { navigator } = globalThis;
const isNoColor =
navigator !== void 0 && navigator.userAgent === 'Cloudflare-Workers'
? await (async () => false)()
: !getColorEnabled();
return !isNoColor;
}
async function main() {
const ua = globalThis.navigator?.userAgent ?? '';
console.log(`navigator.userAgent=${ua || '<missing>'}`);
if (!globalThis.navigator || ua === 'Cloudflare-Workers') {
console.log('skipping dead-await fast-path regression outside the normal fast path');
return;
}
const iterations = Number(process.env.ANT_ASYNC_DEAD_AWAIT_ITERS || 8000);
const ratioLimit = Number(process.env.ANT_ASYNC_DEAD_AWAIT_RATIO_LIMIT || 6);
const wrap = await bench('asyncWrapSync', iterations, asyncWrapSync);
const guard = await bench('navGuardOnly', iterations, navGuardOnly);
const dead = await bench('deadAwaitBranch', iterations, deadAwaitBranch);
const real = await bench('getColorEnabledAsync', iterations, getColorEnabledAsync);
const deadVsWrap = dead.usPerOp / wrap.usPerOp;
const deadVsGuard = dead.usPerOp / guard.usPerOp;
const realVsGuard = real.usPerOp / guard.usPerOp;
console.log(`deadAwaitBranch/asyncWrapSync ratio=${deadVsWrap.toFixed(2)}x`);
console.log(`deadAwaitBranch/navGuardOnly ratio=${deadVsGuard.toFixed(2)}x`);
console.log(`getColorEnabledAsync/navGuardOnly ratio=${realVsGuard.toFixed(2)}x`);
if (deadVsWrap > ratioLimit || deadVsGuard > ratioLimit) {
throw new Error(
'untaken await branch regressed the async fast path ' +
`(ratios ${deadVsWrap.toFixed(2)}x/${deadVsGuard.toFixed(2)}x, limit ${ratioLimit}x)`
);
}
}
main().catch((error) => {
console.error(error && error.stack ? error.stack : String(error));
process.exitCode = 1;
});

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