Add formatters log option (#1905)

Author: KatelynKim

browser.js

@@ -325,32 +325,31 @@ function createWrap (self, opts, rootLogger, level) {
 
 function asObject (logger, level, args, ts, formatters = {}) {
   const {
-    level: levelFormatter
+    level: levelFormatter = () => logger.levels.values[level],
+    log: logObjectFormatter = (obj) => obj
   } = formatters
   if (logger._serialize) applySerializers(args, logger._serialize, logger.serializers, logger._stdErrSerialize)
   const argsCloned = args.slice()
   let msg = argsCloned[0]
-  const o = {}
+  const logObject = {}
   if (ts) {
-    o.time = ts
-  }
-  if (levelFormatter) {
-    const formattedLevel = levelFormatter(level, logger.levels.values[level])
-    Object.assign(o, formattedLevel)
-  } else {
-    o.level = logger.levels.values[level]
+    logObject.time = ts
   }
+  logObject.level = levelFormatter(level, logger.levels.values[level])
+
   let lvl = (logger._childLevel | 0) + 1
   if (lvl < 1) lvl = 1
   // deliberate, catching objects, arrays
   if (msg !== null && typeof msg === 'object') {
     while (lvl-- && typeof argsCloned[0] === 'object') {
-      Object.assign(o, argsCloned.shift())
+      Object.assign(logObject, argsCloned.shift())
     }
     msg = argsCloned.length ? format(argsCloned.shift(), argsCloned) : undefined
   } else if (typeof msg === 'string') msg = format(argsCloned.shift(), argsCloned)
-  if (msg !== undefined) o.msg = msg
-  return o
+  if (msg !== undefined) logObject.msg = msg
+
+  const formattedLogObject = logObjectFormatter(logObject)
+  return formattedLogObject
 }
 
 function applySerializers (args, serialize, serializers, stdErrSerialize) {

test/browser.test.js

@@ -189,6 +189,30 @@ test('opts.browser.formatters logs pino-like object to console', ({ end, ok, is
   end()
 })
 
+test('opts.browser.formatters logs pino-like object to console', ({ end, ok, is }) => {
+  const info = console.info
+  console.info = function (o) {
+    is(o.level, 30)
+    is(o.msg, 'test')
+    is(o.hello, 'world')
+    is(o.newField, 'test')
+    ok(o.time, `Logged at ${o.time}`)
+    console.info = info
+  }
+  const instance = require('../browser')({
+    browser: {
+      formatters: {
+        log (o) {
+          return { ...o, newField: 'test', time: `Logged at ${o.time}` }
+        }
+      }
+    }
+  })
+
+  instance.info({ hello: 'world' }, 'test')
+  end()
+})
+
 test('opts.browser.write func log single string', ({ end, ok, is }) => {
   const instance = pino({
     browser: {