test: add test for dynamically enabling node.async_hooks tracing

test/parallel/test-trace-events-async-hooks-dynamic.js

@@ -0,0 +1,83 @@
+'use strict';
+
+const common = require('../common');
+if (!process.binding('config').hasTracing)
+  common.skip('missing trace events');
+
+const assert = require('assert');
+const cp = require('child_process');
+const fs = require('fs');
+const path = require('path');
+const util = require('util');
+
+const enable = `require("trace_events").createTracing(
+{ categories: ["node.async_hooks"] }).enable();`;
+const code =
+  'setTimeout(() => { for (var i = 0; i < 100000; i++) { "test" + i } }, 1)';
+
+const tmpdir = require('../common/tmpdir');
+const filename = path.join(tmpdir.path, 'node_trace.1.log');
+
+tmpdir.refresh();
+const proc = cp.spawnSync(
+  process.execPath,
+  ['-e', enable + code ],
+  {
+    cwd: tmpdir.path,
+    env: Object.assign({}, process.env, {
+      'NODE_DEBUG_NATIVE': 'tracing',
+      'NODE_DEBUG': 'tracing'
+    })
+  });
+console.log(proc.signal);
+console.log(proc.stderr.toString());
+assert.strictEqual(proc.status, 0);
+
+assert(fs.existsSync(filename));
+const data = fs.readFileSync(filename, 'utf-8');
+const traces = JSON.parse(data).traceEvents;
+assert(traces.length > 0);
+// V8 trace events should be generated.
+assert(!traces.some((trace) => {
+  if (trace.pid !== proc.pid)
+    return false;
+  if (trace.cat !== 'v8')
+    return false;
+  if (trace.name !== 'V8.ScriptCompiler')
+    return false;
+  return true;
+}));
+
+// C++ async_hooks trace events should be generated.
+assert(traces.some((trace) => {
+  if (trace.pid !== proc.pid)
+    return false;
+  if (trace.cat !== 'node,node.async_hooks')
+    return false;
+  return true;
+}));
+
+// JavaScript async_hooks trace events should be generated.
+assert(traces.some((trace) => {
+  if (trace.pid !== proc.pid)
+    return false;
+  if (trace.cat !== 'node,node.async_hooks')
+    return false;
+  if (trace.name !== 'Timeout')
+    return false;
+  return true;
+}));
+
+// Check args in init events
+const initEvents = traces.filter((trace) => {
+  return (trace.ph === 'b' && !trace.name.includes('_CALLBACK'));
+});
+for (const trace of initEvents) {
+  console.log(trace);
+  if (trace.args.data.executionAsyncId > 0 &&
+    trace.args.data.triggerAsyncId > 0) {
+    continue;
+  }
+  assert.fail('Unexpected initEvent: ',
+              util.inspect(trace, { depth: Infinity }));
+}