src: trace_events: support for metadata events

Add support for metadata events. At this point they are added to the
main buffer. Emit a metadata event for the main thread.

PR-URL: https://github.com/nodejs/node/pull/20757
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/test/parallel/test-trace-events-none.js b/test/parallel/test-trace-events-none.js
index 6b60ce999a..a3f0338f28 100644
--- a/test/parallel/test-trace-events-none.js
+++ b/test/parallel/test-trace-events-none.js
@@ -2,6 +2,7 @@
 const common = require('../common');
 const assert = require('assert');
 const cp = require('child_process');
+const fs = require('fs');
 
 const CODE =
   'setTimeout(() => { for (var i = 0; i < 100000; i++) { "test" + i } }, 1)';
@@ -17,5 +18,10 @@ const proc_no_categories = cp.spawn(
 );
 
 proc_no_categories.once('exit', common.mustCall(() => {
-  assert(!common.fileExists(FILE_NAME));
+  assert(common.fileExists(FILE_NAME));
+  // Only __metadata categories should have been emitted.
+  fs.readFile(FILE_NAME, common.mustCall((err, data) => {
+    assert.ok(JSON.parse(data.toString()).traceEvents.every(
+      (trace) => trace.cat === '__metadata'));
+  }));
 }));