Handle disconnecting during publish.

[timoxley]

You may have noticed the following error being logged when running the integration tests:

Error: WebSocket is not open: readyState 2 (CLOSING)

https://travis-ci.com/streamr-dev/streamr-client-javascript/jobs/191090350#L2869-L2884

The above gets logged during running the current integration tests, yet the test suite does not fail because no test is actually listening for the client 'error' event at the time it occurs. It seems to be caused by the test suite itself not waiting for the publish action to finish before disconnecting the client. It appears the message does fail to be published.

Note the code below from the current master branch:

streamr-client-javascript/src/StreamrClient.js

Lines 269 to 272 in 39db82d

	if (this.isConnected()) {
	const streamMessage = await this.msgCreationUtil.createStreamMessage(streamObjectOrId, data, timestamp, partitionKey)
	return this._requestPublish(streamMessage, sessionToken)
	} else if (this.options.autoConnect) {

createStreamMessage is async, so it's entirely possible that the client will fully or partially disconnect between the first isConnected check and createStreamMessage resolving. This causes the _requestPublish to try writing to the disconnecting websocket, which in turn triggers the above error event, which isn't caught by anything.

This PR makes publish re-check the client is connected try to reconnect if autoConnect is set, or fail with an error "Disconnected before publish" otherwise.

Also adjusted the tests that initially exhibited this error to await their operations before continuing.

---

Update: Noticed similar behaviour for subscriptions: if you call client.disconnect() on subscribed, and the subscription had resend options, the client will cough up a similar error event as it tries to write to a closing websocket:

  console.error src/StreamrClient.js:229
    Error: WebSocket is not open: readyState 2 (CLOSING)
        at WebSocket.send (/Users/timoxley/Projects/streamr/streamr-client/node_modules/ws/lib/websocket.js:322:19)
        at Connection.send (/Users/timoxley/Projects/streamr/streamr-client/src/Connection.js:108:25)
        at send (/Users/timoxley/Projects/streamr/streamr-client/src/StreamrClient.js:559:29)
        at <anonymous>
        at process._tickCallback (internal/process/next_tick.js:189:7)

Solved this in 1fbd711 by simply ignoring resend requests if the client is no longer connected. A more general solution should probably be found.

Changes addressed in e2e9a19.

[hpihkala]

Changes LGTM, only added a comment to your comment.