Class: WP_View_Config_Data  - X-Ref

Holds an entity's view configuration while it is being built.

An instance of this class is what `get_entity_view_config_{$kind}_{$name}`
filter callbacks receive: a callback changes the configuration by calling
methods on the instance and returning it. The configuration has four
top-level keys — `default_view`, `default_layouts`, `view_list`, and
`form` — and there are three ways to contribute. They form a gradient of how
deep the replacement reaches:

- The `merge()` method merges partial changes (patches) into what is already
there: `default_view`, `default_layouts`, and the `form` settings by key,
and the `view_list` entries by view `slug` identity. This is what plugins
should use: patches compose with core's configuration and with other
plugins'.
- `replace()` applies a patch the same way `merge()` does, with one
difference: a list in the patch replaces the current list wholesale
instead of merging into it by member identity. It shouldn't be the
default choice — a callback that replaces a list stops inheriting core's
future additions to it — but it's useful when a contributor needs to pin
a list to an exact set of members.
- `set()` goes one step further: it replaces each top-level key the patch
names wholesale, dropping whatever that key held instead of merging into
it. It's for a callback that owns a key outright and wants to pin it to an
exact shape without the inherited default leaking through a key-by-key
merge.

All three touch only the top-level keys the patch names — an omitted key
keeps whatever it had, and a top-level `null` value drops the key it names,
which resets it to its default. They differ only in how deep the replacement
reaches once a key is named: `merge()` and `replace()` merge the value in
key by key (an associative array merges member by member, a nested `null`
deletes just that leaf, a scalar replaces just that value), while `set()`
swaps the whole value. A nested `null` deletes just the leaf it names in
every case. A patch value whose shape does not match the current value —
an associative array where a list lives, or the reverse — is rejected with
a notice rather than merged, and an empty array under `merge()` is a
no-op. Each patch also declares the configuration schema
version it was written against (currently 1), so a future WordPress release
that changes the configuration shape can migrate existing patches forward
instead of breaking them.

Where those three write values, `remove()` deletes them: it takes a spec of
names — a list to delete entries at a level, or a nested map to reach deeper —
and prunes just what it names, mirroring the configuration's shape all the way
down to individual list members.