feat: Allow file to be a function

README.md

@@ -46,6 +46,7 @@ You can specify any of [Sonic-Boom options](https://github.com/pinojs/sonic-boom
   Number will be appened to this file name.
   When the parent folder already contains numbered files, numbering will continue based on the highest number.
   If this path does not exist, the logger with throw an error unless you set `mkdir` to `true`.
+  `file` may also be a function that returns a string.
 
 * `size?`: the maximum size of a given log file.
   Can be combined with frequency.

lib/utils.js

@@ -62,14 +62,19 @@ function getNext (frequency) {
   return getNextCustom(frequency)
 }
 
-function buildFileName (fileName, lastNumber = 1, extension) {
-  if (!fileName) {
+function getFileName (fileVal) {
+  if (!fileVal) {
     throw new Error('No file name provided')
   }
-  return `${fileName}.${lastNumber}${extension ?? ''}`
+  return typeof fileVal === 'function' ? fileVal() : fileVal
 }
 
-async function detectLastNumber (fileName, time = null) {
+function buildFileName (fileVal, lastNumber = 1, extension) {
+  return `${getFileName(fileVal)}.${lastNumber}${extension ?? ''}`
+}
+
+async function detectLastNumber (fileVal, time = null) {
+  const fileName = getFileName(fileVal)
   try {
     const numbers = await readFileTrailingNumbers(dirname(fileName), time)
     return numbers.sort((a, b) => b - a)[0]
@@ -102,4 +107,4 @@ async function isMatchingTime (filePath, time) {
   return birthtimeMs >= time
 }
 
-module.exports = { buildFileName, detectLastNumber, parseFrequency, getNext, parseSize }
+module.exports = { buildFileName, detectLastNumber, parseFrequency, getNext, parseSize, getFileName }

pino-roll.js

@@ -3,12 +3,19 @@
 const SonicBoom = require('sonic-boom')
 const { buildFileName, detectLastNumber, parseSize, parseFrequency, getNext } = require('./lib/utils')
 
+/**
+ * A function that returns a string path to the base file name
+ *
+ * @typedef {function} LogFilePath
+ * @returns {string}
+ */
+
 /**
  * @typedef {object} Options
  *
- * @property {string} file - Absolute or relative path to the log file.
+ * @property {string|LogFilePath} file - Absolute or relative path to the log file.
  * Your application needs the write right on the parent folder.
- * Number will be appened to this file name.
+ * Number will be appended to this file name.
  * When the parent folder already contains numbered files, numbering will continue based on the highest number.
  * If this path does not exist, the logger with throw an error unless you set `mkdir` to `true`.
  *

test/lib/utils.test.js

@@ -5,7 +5,7 @@ const { writeFile, rm, stat } = require('fs/promises')
 const { join } = require('path')
 const { test } = require('tap')
 
-const { buildFileName, detectLastNumber, getNext, parseFrequency, parseSize } = require('../../lib/utils')
+const { buildFileName, detectLastNumber, getNext, parseFrequency, parseSize, getFileName } = require('../../lib/utils')
 const { cleanAndCreateFolder, sleep } = require('../utils')
 
 test('parseSize()', async ({ equal, throws }) => {
@@ -54,10 +54,18 @@ test('getNext()', async ({ same, throws }) => {
   same(getNext(custom), Date.now() + custom, 'supports custom frequency and does not return start')
 })
 
+test('getFileName()', async ({ equal, throws }) => {
+  const strFunc = () => 'my-func'
+  throws(getFileName, 'throws on empty input')
+  equal(getFileName('my-file'), 'my-file', 'returns string when string given')
+  equal(getFileName(strFunc), 'my-func', 'invokes function when function given')
+})
+
 test('buildFileName()', async ({ equal, throws }) => {
   const ext = '.json'
   throws(buildFileName, 'throws on empty input')
   equal(buildFileName('my-file'), 'my-file.1', 'appends 1 by default')
+  equal(buildFileName(() => 'my-func'), 'my-func.1', 'appends 1 by default')
   equal(buildFileName('my-file', 5, ext), 'my-file.5.json', 'appends number and extension')
 })
 
@@ -67,11 +75,13 @@ test('detectLastNumber()', async ({ test, beforeEach }) => {
 
   test('given existing files', async ({ equal }) => {
     const fileName = join(folder, 'file.5')
+    const fileNameFunc = () => fileName
     await writeFile(join(folder, 'file.1'), '')
     await writeFile(join(folder, 'file.5'), '')
     await writeFile(join(folder, 'file.10'), '')
     await writeFile(join(folder, 'file.7'), '')
     equal(await detectLastNumber(fileName), 10, 'detects highest existing number')
+    equal(await detectLastNumber(fileNameFunc), 10, 'detects highest existing number when given func')
   })
 
   test('given existing files and a time', async ({ equal }) => {

test/pino-roll.test.js

@@ -1,9 +1,10 @@
 'use strict'
 
 const { once } = require('events')
-const { stat, readFile, writeFile } = require('fs/promises')
+const { stat, readFile, writeFile, readdir } = require('fs/promises')
 const { join } = require('path')
 const { test, beforeEach } = require('tap')
+const { format } = require('date-fns')
 
 const { buildStream, cleanAndCreateFolder, sleep } = require('./utils')
 
@@ -35,6 +36,21 @@ test('rotate file based on time', async ({ ok, notOk, rejects }) => {
   rejects(stat(`${file}.4`), 'no other files created')
 })
 
+test('rotate file based on time and parse filename func', async ({ ok, notOk, rejects }) => {
+  const file = join(logFolder, 'log')
+  const fileFunc = () => `${file}-${format(new Date(), 'HH-mm-ss-SSS')}`
+  const stream = await buildStream({ frequency: 100, file: fileFunc })
+  stream.write('logged message #1\n')
+  stream.write('logged message #2\n')
+  await sleep(110)
+  stream.write('logged message #3\n')
+  stream.write('logged message #4\n')
+  await sleep(110)
+  stream.end()
+  const files = await readdir(logFolder)
+  ok(files.length === 3, 'created three files')
+})
+
 test('rotate file based on size', async ({ ok, rejects }) => {
   const file = join(logFolder, 'log')
   const size = 20