Support User: Add Redux integration

[jordwest]

Previous PR: #2368

This change adds the Redux actions and reducer for the Support User UI in an upcoming PR. There are no changes to functionality in this PR.

Ref: p195om-2GO-p2

cc @gwwar

[gwwar]

Also cc @aduth @dmsnell

[dllh]

I tested the functionality a bit and it's working as I'd expect. The code looks good to me, but I'd rather have more experienced eyes on it to thumbs up a merge.

[gwwar]

Any reason why you're hiding the function signature here?

[dmsnell]

Or go crazy and skip the arguments…

const storeDispatch = reduxStore.dispatch.bind( reduxStore );

window.supportUser = {
    login: compose( storeDispatch, supportUserFetchToken ),
    logout: compose( storeDispatch, supportUserRestore )
}

😄

[gwwar]

👍 This looks pretty good to me and works. To be safe, I'd get another +1 from @aduth or @dmsnell.

Also, should we update the selector for current user to also know about the support user?

[dmsnell]

how about instead of merging this into a nested structure we just abort early

if ( error ) {
    return callback( error );
}

this.once( 'change', callback ); // no need to create a closure for calling callback
this.clear();
this.fetch();

[dmsnell]

Looks pretty good @jordwest - sure would be nice to see some tests here to verify this!

[aduth]

There's quite a few side-effects occurring in the functions of this file. The action creators should really only be returning simple objects (or in the case of thunks, dispatching objects as asynchronously). It seems that these are needed for interoperability between the old-style user store, though I'd argue that we should start to manage the behavior of the current user exclusively from client/state/current-user.

[dmsnell]

I second what @aduth is saying here, though withheld my comments previously because it seemed to be mostly stage one in moving the legacy code to Redux. But consider this a plus one, a bump, or a thumbs-up to what he said 😉

[jordwest]

Thirded. I was also hesitant writing these calls in the action creators, but at this stage I can't think of another way around it until User and UserSettings libraries are fully connected to the Redux store. That looks like a fairly sizeable task in itself and at the moment HEs are pretty keen to start using this feature; would you both be happy with this as is for a temporary solution and we can revisit later?

[dmsnell]

That's fine with me, which is why I didn't originally bring it up. I'd rather have it here than in the store.

[mtias]

There's another issue with these intermediary steps that affect the purity of the state — for part of our offline strategy we are dumping state into storage and hydrating on boot, we are also exploring queues of actions to be replayed later on. Anything that affects what's expected of a pure redux flow would add obstacles in the way. I'm of the mind that as long as we have coexisting data structures we need to duplicate code and handle it in both places, or fully rework the old code to the new state tree.

[aduth]

Result of eslint client/state/support:

/Users/andrew/Documents/Code/wp-calypso/client/state/support/actions.js
  16:3   warning  Trailing spaces not allowed             no-trailing-spaces
  34:33  warning  "userData" is defined but never used    no-unused-vars
  34:46  warning  Trailing spaces not allowed             no-trailing-spaces
  37:42  warning  Trailing spaces not allowed             no-trailing-spaces
  58:1   warning  Missing JSDoc for parameter 'userData'  valid-jsdoc
  72:1   warning  Missing JSDoc for parameter 'error'     valid-jsdoc

/Users/andrew/Documents/Code/wp-calypso/client/state/support/reducer.js
  22:40  warning  "userData" is already declared in the upper scope  no-shadow
  29:1   warning  Trailing spaces not allowed                        no-trailing-spaces
  49:1   warning  Missing JSDoc parameter description for 'state'    valid-jsdoc
  49:1   warning  Missing JSDoc parameter description for 'action'   valid-jsdoc
  49:1   warning  Missing JSDoc return description                   valid-jsdoc

✖ 11 problems (0 errors, 11 warnings)

[jordwest]

Thanks for the feedback @dllh, @gwwar, @mtias, @dmsnell, @aduth. Based on the discussion above, I went back to the drawing board and came up with a way to decouple the Redux store from the low-level parts, and re-implemented this PR in #2819. It removes any side-effects in the action creators, while a support-user-interop module observes the Redux store and passes any changes down to the wpcom module. Would appreciate any review :)

I'll close this PR for now as #2819 replaces it.