child schemas set to false causes parent to get timestamps when parent timestamps set to false

[lineus]

re: @YouriT 's comment on #7074

7202.js

#!/usr/bin/env node
'use strict';

const assert = require('assert');
const mongoose = require('mongoose');
const { Schema, connection} = mongoose;

const DB = '7202';
const URI = `mongodb://localhost:27017/${DB}`;
const OPTS = { family: 4, useNewUrlParser: true };

const subSchema = new Schema({}, { timestamps: false });
const schema = new Schema({ sub: subSchema }, { timestamps: false });

const Test = mongoose.model('test', schema);
const test = new Test({ sub: {} });

function strictEqual(a, b, msg) {
  try {
    assert.strictEqual(a, b, msg);
  } catch (e) {
    console.error(e.message);
  }
}

async function run() {
  assert.strictEqual(mongoose.version, '5.3.8');
  await mongoose.connect(URI, OPTS);
  await connection.dropDatabase();
  const doc = await Test.create(test);
  assert.ok(doc);
  strictEqual(doc.updatedAt, undefined, 'parent has createdAt set.');
  strictEqual(doc.createdAt, undefined, 'parent has updatedAt set.');
  strictEqual(doc.sub.createdAt, undefined, 'child has createdAt set.');
  strictEqual(doc.sub.updatedAt, undefined, 'child has updatedAt set.');
  await connection.close();
}

run();

Output:

issues: ./7202.js
parent has createdAt set.
parent has updatedAt set.
issues:

[YouriT]

@lineus I believe the only required modification is to expand the one you did in #7074.

lib/schema.js#L857

const childHasTimestamp = this.childSchemas.
  find(s => s.schema.options.timestamps != null);

if (!timestamps && !childHasTimestamp) {
  return;
}

Just replace

s => s.schema.options.timestamps != null

by

s => s.schema.options.timestamps === true || s.schema.options.timestamps == null

And the test will pass.