feat(addHandler): Allow log event filters to be specified

BREAKING CHANGE: Handler funtion is no longer optional for either `addHandler` or `removeHandler`. Used to default to `defaultHandler`.

index.test.ts

@@ -111,6 +111,68 @@ test('adding and removing handlers', () => {
   expect(consoleError.mock.calls.length).toBe(consoleErrorCalls)
 })
 
+test('adding a handler with filter options', () => {
+  const log1 = getLogger('log1')
+  const log2 = getLogger('log2')
+  removeHandlers()
+
+  let lastMessage
+  const recordMessage = (logData: LogData) => (lastMessage = logData.message)
+
+  // No filter
+  const handler1 = addHandler(recordMessage)
+  log1.debug('A')
+  expect(lastMessage).toBe('A')
+  removeHandler(handler1)
+
+  // tags filter
+  const handler2 = addHandler(recordMessage, { tags: ['log1'] })
+  log1.debug('B')
+  log2.debug('C')
+  expect(lastMessage).toBe('B')
+  removeHandler(handler2)
+
+  // maxLevel filter
+  const handler3 = addHandler(recordMessage, { maxLevel: LogLevel.error })
+  log1.error('D')
+  log1.debug('E')
+  expect(lastMessage).toBe('D')
+  removeHandler(handler3)
+
+  // messageRegex filter
+  const handler4 = addHandler(recordMessage, { messageRegex: /^F$/ })
+  log1.debug('F')
+  log1.debug('f')
+  log1.debug('')
+  log1.debug(' FF')
+  expect(lastMessage).toBe('F')
+  removeHandler(handler4)
+
+  // func filter
+  const handler5 = addHandler(recordMessage, {
+    func: (logData: LogData): boolean =>
+      logData.level === LogLevel.debug && logData.message.startsWith('G')
+  })
+  log1.debug('G')
+  log1.debug('g')
+  log1.error('Goof')
+  expect(lastMessage).toBe('G')
+  removeHandler(handler5)
+
+  // All the filters together
+  const handler6 = addHandler(recordMessage, {
+    tags: ['log2'],
+    maxLevel: LogLevel.warn,
+    messageRegex: /^H/,
+    func: (logData: LogData): boolean => logData.message.endsWith('!')
+  })
+  log2.warn('Hello world!')
+  log2.debug('Help!')
+  log1.error('Hello woof!')
+  expect(lastMessage).toBe('Hello world!')
+  removeHandler(handler6)
+})
+
 test('defaultHandler:level', () => {
   const log = getLogger('logger')
 

index.ts

@@ -148,25 +148,51 @@ export function handlers(): LogHandler[] {
 /**
  * Add a handler.
  *
- * @param handler A function that handles the log data. Defaults to `defaultHandler`.
+ * @param handler A function that handles the log data.
+ * @param filter Options for filtering log data prior to sending to the handler.
+ * @param filter.tags A list of tags that the log data should match.
+ * @param filter.maxLevel The maximum log level.
+ * @param filter.messageRegex A regex that the log level should match.
+ * @param filter.func A function that determines if handler is called
  * @returns The handler function that was added.
  */
-export function addHandler(handler?: LogHandler): LogHandler {
-  if (handler === undefined) handler = defaultHandler
-  bus.addListener(LOG_EVENT_NAME, handler)
-  return handler
+export function addHandler(
+  handler: LogHandler,
+  filter: {
+    tags?: string[]
+    maxLevel?: LogLevel
+    messageRegex?: RegExp
+    func?: (logData: LogData) => boolean
+  } = {}
+): LogHandler {
+  let listener = handler
+  const { tags, maxLevel, messageRegex, func } = filter
+  if (
+    tags !== undefined ||
+    maxLevel !== undefined ||
+    messageRegex !== undefined ||
+    func !== undefined
+  ) {
+    listener = (logData: LogData) => {
+      if (tags !== undefined && !tags.includes(logData.tag)) return
+      if (maxLevel !== undefined && logData.level > maxLevel) return
+      if (messageRegex !== undefined && !messageRegex.test(logData.message))
+        return
+      if (func !== undefined && !func(logData)) return
+      handler(logData)
+    }
+  }
+  bus.addListener(LOG_EVENT_NAME, listener)
+  return listener
 }
 
 /**
  * Remove a handler.
  *
- * @param handler The handler function to remove. Defaults to `defaultHandler`.
+ * @param handler The handler function to remove.
  */
-export function removeHandler(handler?: LogHandler): void {
-  bus.removeListener(
-    LOG_EVENT_NAME,
-    handler !== undefined ? handler : defaultHandler
-  )
+export function removeHandler(handler: LogHandler): void {
+  bus.removeListener(LOG_EVENT_NAME, handler)
 }
 
 /**