Remove obsolete locale-specific files on upgrade

[SergeyBiryukov]

We used to have wp-content/languages/ru_RU.css file in ru_RU package.

Since #19603, it's no longer needed, but is still left over on upgrade. We should probably include it in $_old_files.

I suppose the same applies to zh_CN and he_IL packages ([19825]).

Yeah — this could also hypothetically result in conflicts for any $locale.php files.

We should be able to script this.

Just noticed that ms-$locale.po and ms-$locale.mo are also left over.

Actually, ru_RU.php could also be removed. It's only used now as a workaround for #20975.

This isn't high priority, but we should probably identify any *.php locale files that we removed from 3.3 to 3.4, and put those in the upgrade routine. Otherwise I imagine they risk causing problems.

Though I posted to ​the P2, I was able to sufficiently script this.

These locales had a locale.php file in their latest 3.3.x build but not in their 3.4 final build: sv_SE
pl_PL
ar
id_ID
nb_NO
fi
en_CA
nn_NO
eo
ckb
pt_BR.

zh_CN, he_IL, and ru_RU still do have locale.php files.

All of these locales are either $wp_default_secret_key or $text_direction, so they are harmless. pl_PL also adds a date declension filter, but again, harmless as-is and won't break core. So, moving to 3.5.

This is not as easy as just adding files to $_old_files, because we have to detect a custom language directory. Here's a patch that is one way to implment this.

Includes some debug to allow for repeated update testing.

Replying to nacin:

These locales had a locale.php file in their latest 3.3.x build but not in their 3.4 final build: sv_SE
pl_PL

pl_PL still uses the locale file, only in a slightly modified form (no $wp_default_secret_key). :)

In hebrew language, he_IL.php is used to add he_IL.css to admin/login head.

Please review me, dd32!

Looks sane, untested, but I assume nacin did that..

Only question is, do we need to be recursively deleting the file?

$wp_filesystem->delete( $old_file, true );

Please don't remove pl_PL.php - the date declension filter is necessary.