pass mkdir option on pino/file transport to pino.destination function (…

…#1223)

docs/transports.md

@@ -240,6 +240,17 @@ const transport = pino.transport({
 pino(transport)
 ```
 
+By default, the `pino/file` transport assumes the directory of the destination file exists. If it does not exist, the transport will throw an error when it attempts to open the file for writing. The `mkdir` option may be set to `true` to configure the transport to create the directory, if it does not exist, before opening the file for writing.
+
+```js
+const pino = require('pino')
+const transport = pino.transport({
+  target: 'pino/file',
+  options: { destination: '/path/to/file', mkdir: true }
+})
+pino(transport)
+```
+
 The `options.destination` property may also be a number to represent a file descriptor. Typically this would be `1` to write to STDOUT or `2` to write to STDERR. If `options.destination` is not set, it defaults to `1` which means logs will be written to STDOUT.
 
 The difference between using the `pino/file` transport builtin and using `pino.destination` is that `pino.destination` runs in the main thread, whereas `pino/file` sets up `pino.destination` in a worker thread.

file.js

@@ -4,7 +4,9 @@ const pino = require('./pino')
 const { once } = require('events')
 
 module.exports = async function (opts = {}) {
-  const destination = pino.destination({ dest: opts.destination || 1, sync: false })
+  const destOpts = { dest: opts.destination || 1, sync: false }
+  if (opts.mkdir) destOpts.mkdir = true
+  const destination = pino.destination(destOpts)
   await once(destination, 'ready')
   return destination
 }

test/transport/core.test.js

@@ -279,6 +279,27 @@ test('pino.transport with target pino/file', async ({ same, teardown }) => {
   })
 })
 
+test('pino.transport with target pino/file and mkdir option', async ({ same, teardown }) => {
+  const folder = '_' + Math.random().toString(36).substr(2, 9)
+  const destination = join(os.tmpdir(), folder, folder)
+  const transport = pino.transport({
+    target: 'pino/file',
+    options: { destination, mkdir: true }
+  })
+  teardown(transport.end.bind(transport))
+  const instance = pino(transport)
+  instance.info('hello')
+  await watchFileCreated(destination)
+  const result = JSON.parse(await readFile(destination))
+  delete result.time
+  same(result, {
+    pid,
+    hostname,
+    level: 30,
+    msg: 'hello'
+  })
+})
+
 test('pino.transport with target pino-pretty', async ({ match, teardown }) => {
   const destination = join(
     os.tmpdir(),