Widgets sidebar and position can't be changed with accessibility mode enabled

[vybiral]

Hello,
in WordPress 6.9 with Block-based widgets editor disabled, sidebar and position of widgets can't be changed in Accessibility Mode.

Steps to reproduce

1) Install clean WordPress 6.9.
2) Install theme with support of multiple widgets areas (e.g. Twenty Seventeen).
3) Disable Block-based widgets editor by installing Classic Widgets plugin or just using built-in filter.

add_filter( 'use_widgets_block_editor', '__return_false' );

4) Go to Appearance – Widgets and click "Enable accessibility mode" at top-right corner.
5) Try to insert any widget (e.g. Custom HTML) with any content into "Footer 1" sidebar. The widget will always be placed at the very last sidebar (which is "Footer 2" in Twenty Seventeen theme, but this behaviour is theme-independent).

Why this should be considered as bug

I know it could be questionable if this is a bug in WordPress core and not just compatibility issue, because to reproduce it, you have to install non-default theme with widgets support and manually turn off Block-based widgets editor. But I believe this should be considered so, because Classic widgets editor including its accessibility mode is still core WordPress feature, which is not just turned on by default.

Thank you.

[sabernhardt]

This seems to be a new bug. I was able to reproduce it in 6.9 but not in 6.8.3.

#52399 is for possibly removing the accessibility mode, if the other classic mode is good enough, but it has not been removed yet.

Trac ticket: https://core.trac.wordpress.org/ticket/64380

[wildworks]

This issue is caused by a variable name ($sidebar_id) collision caused by [61187].

​The sidebar selected by the user is overwritten each time ​this loop runs, resulting in widgets being unintentionally added to the last sidebar.

I've submitted ​PR 10633, but if you have any ideas for better variable names, please let me know.

Thanks both of you for the reviews! I'll commit this PR.

[wildworks]

In 61399:

Widgets: Insert widgets into the selected sidebar correctly in accessibility mode.

Renames variables to resolve conflict with outer scope variables, fixing widget placement in selected sidebars.

Props joedolson, sabernhardt, vybiral, wildworks.
Fixes #64380.

[wildworks]

Reopening #64380 to request backporting [61399] to 6.9 branch