Specify "constants" for notifier query string parameters

[ycombinator]

This way, if some piece of code wanted use these query string parameters, they don't have to worry about the parameters' names changing. They would use these "constants" instead to construct the query string as shown below:

import Notifier from 'ui/notify/notifier';
const queryString = `?${Notifier.QS_PARAM_MESSAGE}=foobarbaz&...`;

[Bargs]

Wouldn't it be better to put this functionality behind setters/getters on the Notifier and allow it to manage it's own state, rather than encouraging client code to directly modify the URL? Anything that touches the URL directly is gonna cause pain when this issue is tackled: #3947

[ycombinator]

@Bargs that would be ideal except we need to pass this state from one app to another. My understanding is that the Notifier keeps its state in memory, which is cleared between page refreshes that happen when apps are changed.

[ycombinator]

Also note that these parameters are cleared from the URL after the Notifier is triggered. Not sure if that will help when #3947 is tackled.

[ycombinator]

@Bargs and I had a conversation off-issue about this so bringing it back into the issue: it might be possible not to use these three custom query string parameters to pass the Notifier state from one app to another. Slightly better might be to use the global state parameter. I'm going to look into that now so this PR is on hold for the moment.

[ycombinator]

@Bargs I looked into using globalState instead of the three custom top-level query string parameters. While I am able to populate the _g query string parameter using the globalState API, I still couldn't get around the issue of making sure that parameter survived a URL change when the app changed.

At this point I think I should continue with this PR as-is. Longer term, we might want to look into making the Notifier state transcend individual apps and/or how we re-route between apps. Thoughts?

[Bargs]

@ycombinator that's fine, I don't think this PR needs to be blocked on it. Thanks for taking a crack at it, and sorry for sending you on a wild goose chase. I see now that this really needs to be solved on a more universal level, outside of the Notifier itself.

[ycombinator]

@tsullivan This is ready for review again.

[tsullivan]

LGTM and seems like it will do what we need for the plugins