Deprecation warning for pino.final() in Node v14+ (#1199)

lib/deprecations.js

@@ -6,3 +6,5 @@ module.exports = warning
 const warnName = 'PinoWarning'
 
 warning.create(warnName, 'PINODEP008', 'prettyPrint is deprecated, look at https://github.com/pinojs/pino-pretty for alternatives.')
+
+warning.create(warnName, 'PINODEP009', 'The use of pino.final is discouraged in Node.js v14+ and not required. It will be removed in the next major version')

lib/tools.js

@@ -437,6 +437,9 @@ function createArgsNormalizer (defaultOptions) {
 }
 
 function final (logger, handler) {
+  const major = Number(process.versions.node.split('.')[0])
+  if (major >= 14) warning.emit('PINODEP009')
+
   if (typeof logger === 'undefined' || typeof logger.child !== 'function') {
     throw Error('expected a pino logger instance')
   }

test/final.test.js

@@ -8,6 +8,29 @@ const { sleep, getPathToNull } = require('./helper')
 // will be emitted. Let's raise this so we do not scare everybody.
 process.setMaxListeners(100)
 
+test('should show warning for pino.final on node 14+', ({ equal, end, plan }) => {
+  const major = Number(process.versions.node.split('.')[0])
+  if (major < 14) return end()
+
+  plan(1)
+  const dest = pino.destination({ dest: getPathToNull(), sync: false })
+  dest.flushSync = () => {}
+  const instance = pino(dest)
+
+  pino.final(instance, (_, finalLogger) => {
+    finalLogger.info('hello')
+  })()
+
+  function onWarning (warning) {
+    equal(warning.code, 'PINODEP009')
+    end()
+  }
+
+  process.once('warning', onWarning)
+
+  instance.info('hello')
+})
+
 test('replaces onTerminated option', async ({ throws }) => {
   throws(() => {
     pino({