test: pubsub.unsubscribe without handler reference (#437)

* docs: unsubscribe with no parameters

* test: add test with many handlers for unsubscribe

* docs: edit unsubscribe explanation

* test: remove setTimeout

* docs: use async/await in unsubscribe

* docs: added extra note on promise

* test: convert unsubscribe use to async api

Author: Isan-Rivkin

SPEC/PUBSUB.md

@@ -50,7 +50,15 @@ A great source of [examples][] can be found in the tests for this API.
 
 If no `callback` is passed, a [promise][] is returned.
 
-This works like `EventEmitter.removeListener`, as that only the `handler` passed to a `subscribe` call before is removed from listening. The underlying subscription will only be canceled once all listeners for a topic have been removed.
+If the `topic` and `handler` are provided, the `handler` will no longer receive updates for the `topic`. This behaves like [EventEmitter.removeListener](https://nodejs.org/dist/latest/docs/api/events.html#events_emitter_removelistener_eventname_listener). If the `handler` is not equivalent to the `handler` provided on `subscribe`, no action will be taken.
+
+If **only** the `topic` param is provided, unsubscribe will remove **all** handlers for the `topic`. This behaves like [EventEmitter.removeAllListeners](https://nodejs.org/dist/latest/docs/api/events.html#events_emitter_removealllisteners_eventname). Use this if you would like to no longer receive any updates for the `topic`.
+
+**WARNING:** Unsubscribe is an async operation, but removing **all** handlers for a topic can only be done using the Promises API (due to the difficulty in distinguishing between a "handler" and a "callback" - they are both functions). If you _need_ to know when unsubscribe has completed you must use `await` or `.then` on the return value from 
+
+```JavaScript
+ipfs.pubsub.unsubscribe('topic')
+```
 
 **Example:**
 
@@ -78,6 +86,17 @@ ipfs.pubsub.subscribe(topic, receiveMsg, (err) => {
 })
 ```
 
+Or removing all listeners: 
+```JavaScript
+const topic = 'fruit-of-the-day'
+const receiveMsg = (msg) => console.log(msg.toString())
+
+await ipfs.pubsub.subscribe(topic, receiveMsg);
+
+// Will unsubscribe ALL handlers for the given topic
+await ipfs.pubsub.unsubscribe(topic);
+```
+
 A great source of [examples][] can be found in the tests for this API.
 
 #### `pubsub.publish`

src/pubsub/unsubscribe.js

@@ -57,5 +57,16 @@ module.exports = (createCommon, options) => {
         )
       })
     })
+
+    it('should subscribe 10 handlers and unsunscribe once with no reference to the handlers', async () => {
+      const count = 10
+      const someTopic = getTopic()
+      for (let i = 0; i < count; i++) {
+        await ipfs.pubsub.subscribe(someTopic, (msg) => {})
+      }
+      await ipfs.pubsub.unsubscribe(someTopic)
+      const topics = await ipfs.pubsub.ls()
+      expect(topics).to.eql([])
+    })
   })
 }