test_tla_dead_await_fastpath.cjs
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test_tla_dead_await_fastpath.cjs
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	const { spawnSync } = require('child_process');
	const fs = require('fs');
	const os = require('os');
	const path = require('path');

	function assert(condition, message) {
	if (!condition) throw new Error(message);
	}

	const tmpRoot = fs.mkdtempSync(path.join(os.tmpdir(), 'ant-tla-dead-await-fastpath-'));
	const modulePath = path.join(tmpRoot, 'bench.mjs');

	fs.writeFileSync(
	modulePath,
	[
	'const now =',
	" typeof performance !== 'undefined' && performance && typeof performance.now === 'function'",
	' ? () => performance.now()',
	' : () => Date.now();',
	'',
	'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;',
	'}',
	'',
	'const ua = globalThis.navigator?.userAgent ?? "";',
	'if (!globalThis.navigator \|\| ua === "Cloudflare-Workers") {',
	' console.log(JSON.stringify({ skipped: true, ua }));',
	' process.exit(0);',
	'}',
	'',
	'const iterations = Number(process.env.ANT_TLA_DEAD_AWAIT_ITERS \|\| 20000);',
	'',
	'const guardStart = now();',
	'for (let i = 0; i < iterations; i++) {',
	' const isNoColor =',
	' navigator !== void 0 && navigator.userAgent === "Cloudflare-Workers"',
	' ? false',
	' : !getColorEnabled();',
	' void isNoColor;',
	'}',
	'const guardMs = now() - guardStart;',
	'',
	'const deadStart = now();',
	'for (let i = 0; i < iterations; i++) {',
	' const isNoColor =',
	' navigator !== void 0 && navigator.userAgent === "Cloudflare-Workers"',
	' ? await (async () => false)()',
	' : !getColorEnabled();',
	' void isNoColor;',
	'}',
	'const deadMs = now() - deadStart;',
	'',
	'console.log(JSON.stringify({',
	' skipped: false,',
	' ua,',
	' iterations,',
	' guardMs,',
	' deadMs,',
	' guardUsPerOp: (guardMs * 1000) / iterations,',
	' deadUsPerOp: (deadMs * 1000) / iterations,',
	'}));',
	'',
	].join('\n')
	);

	const result = spawnSync(process.execPath, [modulePath], {
	encoding: 'utf8',
	});

	if (result.error) throw result.error;
	assert(
	result.status === 0,
	`expected module benchmark to exit 0, got ${result.status}\nstdout:\n${result.stdout}\nstderr:\n${result.stderr}`
	);

	const output = result.stdout.trim();
	assert(output.length > 0, `expected benchmark JSON output, got stdout=${JSON.stringify(result.stdout)}`);

	const parsed = JSON.parse(output);
	console.log(`navigator.userAgent=${parsed.ua \|\| '<missing>'}`);

	if (parsed.skipped) {
	console.log('skipping TLA dead-await fast-path regression outside the normal fast path');
	process.exit(0);
	}

	const ratioLimit = Number(process.env.ANT_TLA_DEAD_AWAIT_RATIO_LIMIT \|\| 6);
	const ratio = parsed.deadUsPerOp / parsed.guardUsPerOp;

	console.log(
	`guard=${parsed.guardUsPerOp.toFixed(3)}us/op dead=${parsed.deadUsPerOp.toFixed(3)}us/op ratio=${ratio.toFixed(2)}x`
	);

	assert(
	ratio <= ratioLimit,
	`untaken TLA await branch regressed the fast path (ratio ${ratio.toFixed(2)}x, limit ${ratioLimit}x)`
	);

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