Correctly label forms in wp_list_table

[joedolson]

Adds labels to current page selector and bulk actions select field so that screen readers have an explicit label for those fields.

Passes $which to bulk_actions method in class-wp-list-table.php and in class-wp-plugins-list-table.php so that IDs on top and bottom forms are unique.

[joedolson]

Labels for wp_list_table inputs

[wonderboymusic]

Every subclass of WP_List_Table needs $which in the method signature for ->bulk_actions()

[wonderboymusic]

oops - nevermind, I was looking at ->get_bulk_actions()

[wonderboymusic]

In 29294:

Adds <label>s to current page selector and bulk actions <select> field so that screen readers have an explicit label.

Props joedolson.
Fixes #28867.

[ocean90]

In 29308:

Add missing screen-reader-text CSS class in [29294].

see #28867.

[tivnet]

bulk_actions( $which ) - the parameter was added without a default value. Old code fails with

Warning: Missing argument 1 for WP_List_Table::bulk_actions()

[jwenerd]

Added a patch which passed empty string as default argument to WP_List_Table::bulk_actions()

Does empty string good for this or is something else more sensible as the default argument?

[DrewAPicture]

@wonderboymusic: I hesitate to signify $which as optional, though I don't have a good solution for back-compat + guaranteeing it holds the value expected. Suggestions?

Side note: I'm happy to write inline docs wherever needed.

[joedolson]

I don't know that there's a ready way to guarantee that it holds the value expected; but I think that having it optional is at least reasonable, since we need to pass something.

If it's optional and not supplied, the inputs will potentially be invalidly labeled due to a repetitive ID value. This would still leave them better labeled than they were prior to this patch, and would not be a regression for old code -- since old code was in an environment that was never correctly labeled in the first place.

Speaking for myself, I think that having the variable be optional is the best option we have right now, and I would accept it.

[wonderboymusic]

[29440] missed the ticket.