test_runner: make sure tap subtest is reported in order

lib/internal/test_runner/test.js

@@ -142,6 +142,7 @@ class TestContext {
 class Test extends AsyncResource {
   #abortController;
   #outerSignal;
+  #reportedSubtest;
 
   constructor(options) {
     super('Test');
@@ -308,7 +309,7 @@ class Test extends AsyncResource {
       }
 
       if (i === 1 && this.parent !== null) {
-        this.reporter.subtest(this.indent, this.name);
+        this.reportSubtest();
       }
 
       // Report the subtest's results and remove it from the ready map.
@@ -631,12 +632,6 @@ class Test extends AsyncResource {
     this.processReadySubtestRange(true);
 
     // Output this test's results and update the parent's waiting counter.
-    if (this.subtests.length > 0) {
-      this.reporter.plan(this.subtests[0].indent, this.subtests.length);
-    } else {
-      this.reporter.subtest(this.indent, this.name);
-    }
-
     this.report();
     this.parent.waitingOn++;
     this.finished = true;
@@ -648,6 +643,11 @@ class Test extends AsyncResource {
   }
 
   report() {
+    if (this.subtests.length > 0) {
+      this.reporter.plan(this.subtests[0].indent, this.subtests.length);
+    } else {
+      this.reportSubtest();
+    }
     let directive;
 
     if (this.skipped) {
@@ -666,6 +666,15 @@ class Test extends AsyncResource {
       this.reporter.diagnostic(this.indent, this.diagnostics[i]);
     }
   }
+
+  reportSubtest() {
+    if (this.#reportedSubtest || this.parent === null) {
+      return;
+    }
+    this.#reportedSubtest = true;
+    this.parent.reportSubtest();
+    this.reporter.subtest(this.indent, this.name);
+  }
 }
 
 class TestHook extends Test {

test/message/test_runner_describe_nested.js

@@ -0,0 +1,10 @@
+// Flags: --no-warnings
+'use strict';
+require('../common');
+const { describe, it } = require('node:test');
+
+describe('nested - no tests', () => {
+  describe('nested', () => {
+    it('nested', () => {});
+  });
+});

test/message/test_runner_describe_nested.out

@@ -0,0 +1,26 @@
+TAP version 13
+# Subtest: nested - no tests
+    # Subtest: nested
+        # Subtest: nested
+        ok 1 - nested
+          ---
+          duration_ms: *
+          ...
+        1..1
+    ok 1 - nested
+      ---
+      duration_ms: *
+      ...
+    1..1
+ok 1 - nested - no tests
+  ---
+  duration_ms: *
+  ...
+1..1
+# tests 1
+# pass 1
+# fail 0
+# cancelled 0
+# skipped 0
+# todo 0
+# duration_ms *