feat: change formatter to output valid json (#40)

* feat: add config to control context inspection depth

* chore: stringify

README.md

@@ -19,7 +19,7 @@ Edit the file in `./config/default.json` to configure the logger, or set the fol
 | `CSL_LOG_FILTER` | Applies a log filter. Specify a comma separated list of individual log levels to be included instead of specifying a `LOG_LEVEL` | `""` | e.g. `"error, trace, verbose" |
 | `CSL_LOG_TRANSPORT` | Selects the transport method. Either `console` or `file`. Uses the same transport for errors and standard logs | `console` | `console`, `file`
 | `CSL_TRANSPORT_FILE_OPTIONS` | _Optional._ Required if `LOG_TRANSPORT=file`. Configures the winston file transport | See `default.json` | See the [Winston Docs](https://github.com/winstonjs/winston#common-transport-options) |
-
+| `CSL_JSON_STRINGIFY_SPACING` |  _Optional._  A number that's used to insert white space into the output JSON string for readability purposes. | 2 | integer
 
 
 

config/default.json

@@ -8,5 +8,6 @@
     "prettyPrint": true,
     "colorize": true,
     "filename": "logs/combined.log"
-  }
-}
+  },
+  "JSON_STRINGIFY_SPACING": 2
+}

package.json

@@ -46,6 +46,7 @@
     "@types/node": "^18.11.9",
     "parse-strings-in-object": "2.0.0",
     "rc": "1.2.8",
+    "safe-stable-stringify": "^2.4.1",
     "winston": "3.8.2"
   },
   "devDependencies": {

src/index.js

@@ -28,26 +28,27 @@
 
 'use strict'
 
-const util = require('util')
 const { createLogger, format, transports } = require('winston')
 const { combine, timestamp, colorize, printf } = format
+const stringify = require('safe-stable-stringify')
 
-const { customLevels, level, logTransport, transportFileOptions } = require('./lib/config')
+const { customLevels, level, logTransport, transportFileOptions, jsonStringifySpacing } = require('./lib/config')
 
 const allLevels = { error: 0, warn: 1, audit: 2, trace: 3, info: 4, perf: 5, verbose: 6, debug: 7, silly: 8 }
 const customLevelsArr = customLevels.split(/ *, */) // extra white space before/after the comma is ignored
 const ignoredLevels = customLevels ? Object.keys(allLevels).filter(key => !customLevelsArr.includes(key)) : []
 
 const customFormat = printf(({ level, message, timestamp, context }) => {
+  let formattedMessage = message
   if (context && context instanceof Object) {
-    message = util.inspect({
+    formattedMessage = {
       ...context,
       message
-    })
+    }
   }
-  return `${timestamp} - ${level}: ${message}`
+  formattedMessage = stringify(formattedMessage, null, jsonStringifySpacing)
+  return `${timestamp} - ${level}: ${formattedMessage}`
 })
-
 let transport = new transports.Console()
 if (logTransport === 'file') {
   transport = new transports.File(transportFileOptions)

src/lib/config.d.ts

@@ -2,3 +2,4 @@ export const customLevels: any;
 export const level: any;
 export const logTransport: any;
 export const transportFileOptions: any;
+export const jsonStringifySpacing: any;

src/lib/config.js

@@ -5,7 +5,8 @@ const Config = {
   customLevels: process.env.LOG_FILTER || RC.LOG_FILTER,
   level: process.env.LOG_LEVEL || RC.LOG_LEVEL,
   logTransport: RC.LOG_TRANSPORT,
-  transportFileOptions: RC.TRANSPORT_FILE_OPTIONS
+  transportFileOptions: RC.TRANSPORT_FILE_OPTIONS,
+  jsonStringifySpacing: RC.JSON_STRINGIFY_SPACING
 }
 
 module.exports = Config

test/unit/index.test.js

@@ -6,6 +6,7 @@ const Winston = require('winston')
 const Proxyquire = require('proxyquire')
 const Logger = require('../../src/index')
 const config = require('../../src/lib/config')
+const stringify = require('safe-stable-stringify')
 
 Test('logger', function (loggerTest) {
   let sandbox
@@ -103,14 +104,34 @@ Test('contextual logger', function (loggerTest) {
   loggerTest.test('logger with context formats message properly', function (assert) {
     const logger = Logger.child({ context: { a: 1 } })
     logger.info('Message')
-    assert.ok(process.stdout.write.firstCall.args[0].split('info\x1B[39m: ')[1] === '{ a: 1, message: \'Message\' }\n')
+    assert.ok(process.stdout.write.firstCall.args[0].split('info\x1B[39m: ')[1] === stringify(
+      { a: 1, message: 'Message' },
+      null,
+      config.jsonStringifySpacing) + '\n')
+    assert.end()
+  })
+
+  loggerTest.test('handles circular references gracefully', function (assert) {
+    const obj1 = {
+      a: 1
+    }
+    const obj2 = {
+      obj1
+    }
+    obj1.newobj2 = obj2
+    const logger = Logger.child({ context: { a: obj2 } })
+    logger.info('Message')
+    assert.ok(process.stdout.write.firstCall.args[0].split('info\x1B[39m: ')[1] === stringify(
+      { a: obj2, message: 'Message' },
+      null,
+      config.jsonStringifySpacing) + '\n')
     assert.end()
   })
 
   loggerTest.test('logger without context formats message properly', function (assert) {
     const logger = Logger.child()
     logger.info('Message')
-    assert.ok(process.stdout.write.firstCall.args[0].split('info\x1B[39m: ')[1] === 'Message\n')
+    assert.ok(process.stdout.write.firstCall.args[0].split('info\x1B[39m: ')[1] === '"Message"\n')
     assert.end()
   })