`wp.api.utils.decorateFromRoute` should use `_.extend` not `_.union`

[Magenta Cuda]

modelInstance.prototype.options = _.union( routeEndpoint.args, modelInstance.prototype.options );

Are not the arguments to _.union objects not arrays? In which case _.extend would be more appropriate.

[adamsilverstein]

@Magenta Cuda thanks for the bug report. I am going to look into this, can I ask you though why you are raising it as a bug, did you come across somewhere trying to use the library and it failed because of this code? eg. does using _.union here vs _.extend actually break something, or are you noting it seems wrong on a pure code bases. If this does cause some demonstrable issue, I'd like to write a unit test demonstrating that so we can verify the code changes fixes the issue.

[adamsilverstein]

@Magenta Cuda

I dug into the code a bit and for our default routes the model prototypes didn't have default options or args, so the _.union call was never reached. You are correct though that args or options at this point would be an object, not an array, so _.extend is more appropriate here.

In 39341.diff​ I fixed up the logic and switched from union to extend. If you have an issue that was caused by this bug I would appreciate if you could test the patch to see if it resolves your issue. I am going to try to add a unit test by mocking a custom endpoint that provides the default args & options this code is designed to extend, see #39264.

Thanks.

[adamsilverstein]

Tracking in ​https://github.com/WP-API/client-js/pull/154

[adamsilverstein]

In 40040:

REST API: JavaScript client should use _.extend when merging objects.

Correct an issue during the client's dynamic route discovery in wp.api.utils.decorateFromRoute where _.union potentially failed if used on objects.

Props ketuchetan.
Fixes #39341.

[SergeyBiryukov]

Reopening for 4.7.3 consideration.

[adamsilverstein]

Replying to SergeyBiryukov:

Reopening for 4.7.3 consideration.

Thanks @SergeyBiryukov!

[dd32]

In 40084:

REST API: JavaScript client should use _.extend when merging objects.

Correct an issue during the client's dynamic route discovery in wp.api.utils.decorateFromRoute where _.union potentially failed if used on objects.

Props ketuchetan, adamsilverstein.
Merges [40040] to the 4.7 branch.
Fixes #39341.