Add default levels to opts in multistream

lib/multistream.js

@@ -13,9 +13,11 @@ function multistream (streamsArray, opts) {
   streamsArray = streamsArray || []
   opts = opts || { dedupe: false }
 
-  let levels = defaultLevels
+  const levels = defaultLevels
   if (opts.levels && typeof opts.levels === 'object') {
-    levels = opts.levels
+    Object.keys(opts.levels).forEach(i => {
+      levels[i] = opts.levels[i]
+    })
   }
 
   const res = {

test/transport/core.test.js

@@ -201,6 +201,30 @@ test('pino.transport with two files and custom levels', async ({ same, teardown
   })
 })
 
+test('pino.transport without specifying default levels', async ({ same, teardown }) => {
+  const dest = file()
+  const transport = pino.transport({
+    targets: [{
+      level: 'foo',
+      target: join(__dirname, '..', 'fixtures', 'to-file-transport.js'),
+      options: { destination: dest }
+    }],
+    levels: { foo: 25 }
+  })
+  teardown(transport.end.bind(transport))
+  const instance = pino(transport)
+  instance.info('hello')
+  await Promise.all([watchFileCreated(dest)])
+  const result1 = JSON.parse(await readFile(dest))
+  delete result1.time
+  same(result1, {
+    pid,
+    hostname,
+    level: 30,
+    msg: 'hello'
+  })
+})
+
 test('pino.transport with two files and dedupe', async ({ same, teardown }) => {
   const dest1 = file()
   const dest2 = file()