TAP event output: plan is miscounted

[SRHerzog]

Version

19.7.0

Platform

Darwin SHerzog-USMAC22.local 22.3.0 Darwin Kernel Version 22.3.0: Mon Jan 30 20:38:37 PST 2023; root:xnu-8792.81.3~2/RELEASE_ARM64_T6000 arm64

Subsystem

test_runner

What steps will reproduce the bug?

These files are copied from the internal test fixtures:

// test/fixtures/test-runner/custom_reporters/custom.js
const assert = require('assert');
const path = require('path');

module.exports = async function * customReporter(source) {
  const counters = {};
  for await (const event of source) {
    // removed assert from original fixture
    counters[event.type] = (counters[event.type] ?? 0) + 1;
  }
  yield "custom.js ";
  yield JSON.stringify(counters);
};

// test/fixtures/test-runner/reporters.js
'use strict';
const test = require('node:test');

test('nested', { concurrency: 4 }, async (t) => {
  t.test('ok', () => {});
  t.test('failing', () => {
    throw new Error('error');
  });
});

test('top level', () => {});

Run node --test-reporter=./custom.js ./reporters.js.

How often does it reproduce? Is there a required condition?

Reproduces consistently.

What is the expected behavior?

The number of "plan" events should be at least as many as the number of tests started. In this case, I would expect the output to be custom.js {"test:start":4,"test:pass":2,"test:fail":2,"test:plan":4,"test:diagnostic":7}

What do you see instead?

custom.js {"test:start":4,"test:pass":2,"test:fail":2,"test:plan":2,"test:diagnostic":7}

Additional information

This behavior may be intertwined with #46762

[SRHerzog]

Had some mistaken assumptions, please disregard.