Error when Publisher component is rendered before rosClient connection hook runs

[JanOlencki]

Hi,

I found an issue in the webviz-core, when the Webviz are connected to the rosbridge via a websocket. If the Publisher component is rendered before the rosClient (roslib.Ros instance) connection hook runs at RosbridgePlayer.js:98 an error listed below occured. It's caused by null reference at RosbridgePlayer.js:331.

Uncaught TypeError: Cannot read property 'idCounter' of undefined
    at Topic.advertise (roslib.js:3360)
    at Topic.publish (roslib.js:3405)
    at exports.default.publish (RosbridgePlayer.js:349)
    at exports.default.publish (index.js:462)
    at exports.default.publish (OrderedStampPlayer.js:153)
    at Object.publish (index.js:251)
    at Publisher.publish (Publisher.js:50)
    at index.js:180
    at index.js:154
    at Object.ka (react-dom.production.min.js:15)

Test case

• Run Webviz connected to ros_bridge via websocket.
• Add Publish panel and set any topic (panel settings will be automatically saved).
• Refresh site.
• Try to publish message by Publish button on Publish panel.
• Probably an error occurred at console, but it depends on timing between described code pieces.

[jaguardo]

I think I have witnessed this effect without an error, but also without a notification that the publish isn't working (simply no feedback of a published message). I've witnessed in both in the current webviz Publish panel and in the @jreyesr PR (Teleop panel), periodically the Publish msg doesn't go through.

Workaround, for both publish panels, if the topic is removed/changed to something else (anything, doesn't even have to be a current topic) and then changed back it will start working.

[jreyesr]

Yes, this bug is especially obnoxious because it shows no feedback on the UI (but there should be an error message on the console, since it's attempting to access a property of an undefined var). I have created a PR that should fix it. I'll wait for feedback on it, then (hopefully) this will be fixed.

[vidaaudrey]

Thank @jreyesr for reporting and trying to fix the issue. Look forward to reviewing the PR.