test: refactor test-sync-io-option

Refactor `test/parallel/test-sync-io-option.js` to be simpler and cover
more cases (in particular, this adds a regression test for
#28913).

Refs: #28913

PR-URL: #29020
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/parallel/test-sync-io-option.js

@@ -1,36 +1,39 @@
 'use strict';
-
-require('../common');
+const common = require('../common');
 const assert = require('assert');
-const execFile = require('child_process').execFile;
+const { promisify } = require('util');
+const execFile = promisify(require('child_process').execFile);
 
-if (process.argv[2] === 'child') {
-  setImmediate(function() {
-    require('fs').readFileSync(__filename);
-    process.exit();
-  });
+// Test that --trace-sync-io works. In particular, a warning should be printed
+// when it is enabled and synchronous I/O happens after the first event loop
+// turn, and no warnings should occur when it is disabled or synchronous I/O
+// happens before the first event loop turn is over.
 
-} else {
-  (function runTest(flags) {
-    const execArgv = [flags.pop()];
-    let args = [__filename, 'child'];
-    let cntr = 0;
-    args = execArgv.concat(args);
-    if (!args[0]) args.shift();
-    execFile(process.execPath, args, function(err, stdout, stderr) {
-      assert.strictEqual(err, null);
-      assert.strictEqual(stdout, '');
-      if (/WARNING[\s\S]*readFileSync/.test(stderr))
-        cntr++;
-      if (args[0] === '--trace-sync-io') {
-        assert.strictEqual(cntr, 1);
-      } else if (args[0] === __filename) {
-        assert.strictEqual(cntr, 0);
-      } else {
-        throw new Error('UNREACHABLE');
-      }
-      if (flags.length > 0)
-        setImmediate(runTest, flags);
-    });
-  }(['--trace-sync-io', '']));
+if (process.argv[2] === 'late-sync-io') {
+  setImmediate(() => {
+    require('fs').statSync(__filename);
+  });
+  return;
+} else if (process.argv[2] === 'early-sync-io') {
+  require('fs').statSync(__filename);
+  return;
 }
+
+(async function() {
+  for (const { execArgv, variant, warnings } of [
+    { execArgv: ['--trace-sync-io'], variant: 'late-sync-io', warnings: 1 },
+    { execArgv: [], variant: 'late-sync-io', warnings: 0 },
+    { execArgv: ['--trace-sync-io'], variant: 'early-sync-io', warnings: 0 },
+    { execArgv: [], variant: 'early-sync-io', warnings: 0 },
+  ]) {
+    const { stdout, stderr } =
+      await execFile(process.execPath, [...execArgv, __filename, variant]);
+    assert.strictEqual(stdout, '');
+    const actualWarnings =
+      stderr.match(/WARNING: Detected use of sync API[\s\S]*statSync/g);
+    if (warnings === 0)
+      assert.strictEqual(actualWarnings, null);
+    else
+      assert.strictEqual(actualWarnings.length, warnings);
+  }
+})().then(common.mustCall());