Editor: CPT: Manage non-hierarchical term edits using Redux state

[nylen]

Similar in approach to #5445.

• 83fe77e is from Editor: Manage post title edits using global Redux state #5445 (dd970a4 in original PR)
• abac80b is from Editor: Manage post title edits using global Redux state #5445 (e03050d in original PR)

To test

Verify no functional changes when editing non-hierarchical CPT terms:

Edit a post of a custom type that has one or more non-hierarchical taxonomies. Ensure that existing taxonomies are loaded correctly in the TokenField:

• values (terms assigned to the saved post)
• suggestions (all terms from the site)

Ensure that terms can be updated and saved as expected.

Test live: https://calypso.live/?branch=update/editor/cpt-term-token-field-redux

[timmyc]

trailing commas. so hot right now.

[nylen]

Found a bug with this logic: if you add a tag then you cannot remove it until saving the draft with the tag added.

[timmyc]

As discussed, we should remove this selector, tests and usage from this PR

[nylen]

Removed in 1e58d39.

[nylen]

The bug is related to the use of _.merge to manipulate post edits: they are accumulated in the reducer logic for EDIT_POST and resolved in the getEditedPost selector.

This is correct and useful for some cases like nested properties, but not for array-like properties where items can be added and removed.

I'll address this by moving from merge to mergeWith using a custom function that does not attempt to merge arrays.

---

On a related note, the Redux state for terms attached to a post is a bit inconsistent because we receive an object like this from the API:

{
    terms: {
        taxonomyName: {
            term1: { ID: 1, ... }
        }
    }
}

and upon editing a (non-hierarchical) taxonomy, we end up with an object like this:

{
    terms: {
        taxonomyName: [ 'termName1', ... ]
    }
}

There are a couple of issues with this:

• Duplicate information in the state tree: the full information for each term is stored in duplicate in the site terms state and in the post state.
• The shape of the terms state on the post object changes based on whether or not it has been edited.

I think the ideal solution for this is to normalize the post terms state in the reducer logic for the POST_RECEIVE action. To accommodate hierarchical terms that can have different parents but the same name, the state for a post should look like this:

{
    terms: {
        taxonomyName: [ {
            ID: 1,
            name: 'termName1',
        }, {
            ...
        } ]
    }
}

I'm inclined to address this in a separate PR, though, since we're waiting for the editor redux code in this PR for a couple of other tasks.

[timmyc]

Related discovery and notes about the discrepancies from the API in #6468

[nylen]

Bug fixed in 6e8f380; marking as Needs Review again.

[timmyc]

Confirmed the bug is fixed with the mergeWith approach. Looking good and testing out in general for me as well. @aduth do you want to give this one a spin?

[aduth]

Couple thoughts here:

Could we get away with a shallow clone? That opens up possibility of mutating the original reference on nested properties (terms, discussion), but I feel that's unlikely to happen.

const edits = {
    ...this.props.edits,
    content: this.refs.editor.getContent()
};

Otherwise, we could make this ever so slightly more efficient by merging the prop edits into the constructed object directly.

const edits = merge( {
    content: this.refs.editor.getContent()
}, this.props.edits );

(Same goes for below where we're created a new merged object with status)

[nylen]

This should be fine - mutating individual elements of the state might cause subtle issues, but no one should be doing that anyway. Done in ae1fb72.