fix(Emit): Only attach stack to errors

Author: nokome

index.test.ts

@@ -20,9 +20,7 @@ test('logging', () => {
   expect(events[0].tag).toBe(TAG)
   expect(events[0].level).toBe(LogLevel.debug)
   expect(events[0].message).toBe('a debug message')
-  expect(events[0].stack).toMatch(/^Error:/)
-  // Second line (first call stack) in stack trace should be this file
-  expect(events[0].stack.split('\n')[1]).toMatch(/logga\/index\.test\.ts/)
+  expect(events[0].stack).toBeUndefined()
 
   log.info({
     message: 'an info message',
@@ -39,6 +37,10 @@ test('logging', () => {
 
   log.error('an error message')
   expect(events[3].level).toBe(LogLevel.error)
+  expect(events[3].stack).toMatch(/^Error:/)
+  // Second line (first call stack) in stack trace should be this file
+  expect(events[3].stack.split('\n')[1]).toMatch(/logga\/index\.test\.ts/)
+
 })
 
 test('TTY', () => {

index.ts

@@ -30,7 +30,8 @@ export interface LogHandler {
  * Take a message `string`, or `LogInfo` object,
  * and emit an event with a `LogData` object.
  *
- * If `LogData` does not have a stack attached, one is generated and set on the `LogData`.
+ * For `LogLevel.error`, if `LogInfo` does not have a `stack`,
+ * one is generated and set on the `LogData`.
  *
  * @param info
  * @param level
@@ -46,7 +47,7 @@ function emitLogData(info: LogInfo | string, tag: string, level: LogLevel) {
   let stack: string
   if (typeof info === 'object' && info.stack) {
     stack = info.stack
-  } else {
+  } else if (level <= LogLevel.error) {
     const error = new Error()
     // Remove the first three lines of the stack trace which
     // are not useful (see issue #3)