fix: mute system logger in local dev (#458)

Follow-up to #457. The system
logger shouldn't be visible in local dev.

src/lib/system_logger.ts

@@ -1,3 +1,5 @@
+import { env } from 'process'
+
 const systemLogTag = '__nfSystemLog'
 
 const serializeError = (error: Error): Record<string, unknown> => {
@@ -28,6 +30,10 @@ class SystemLogger {
   }
 
   private doLog(logger: typeof console.log, message: string) {
+    if (env.NETLIFY_DEV && !env.NETLIFY_ENABLE_SYSTEM_LOGGING) {
+      return
+    }
+
     logger(systemLogTag, JSON.stringify({ msg: message, fields: this.fields }))
   }
 

test/unit/system_logger.js

@@ -1,3 +1,5 @@
+const process = require("process")
+
 const test = require('ava')
 
 const { systemLogger, LogLevel } = require('../../dist/internal')
@@ -35,3 +37,23 @@ test('Fields', (t) => {
 
   console.log = originalLog
 })
+
+test('Local Dev', (t) => {
+  const originalLog = console.log
+  const logs = []
+  console.log = (...message) => logs.push(message)
+  systemLogger.log('hello!')
+  t.is(logs.length, 1)
+
+  process.env.NETLIFY_DEV= "true"
+  systemLogger.log('hello!')
+  t.is(logs.length, 1)
+
+  process.env.NETLIFY_ENABLE_SYSTEM_LOGGING= "true"
+  systemLogger.log('hello!')
+  t.is(logs.length, 2)
+
+  delete process.env.NETLIFY_DEV
+  delete process.env.NETLIFY_ENABLE_SYSTEM_LOGGING
+  console.log = originalLog
+})