[TASK][TRAC-13103] Check DB_CHARSET before installing WP Core

[ramonfincken]

Trac ticket: https://core.trac.wordpress.org/ticket/13103

This will check the DB_CHARSET compatibility upon installing, preventing a non-supported (defined) DB_CHARSET to be used in DB installer.

Based on 13103.patch​ (816 bytes) - added by SergeyBiryukov 14 years ago.
Updated for latest (current) trunk version of git-ified WP Core.

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[mukeshpanchal27]

Thanks @ramonfincken for the PR!

Let some initial feedbacks

[mikachan]

Thanks for working on this, @ramonfincken! I've left a few inline comments.

[mikachan]

Thanks for the changes! I've left a couple more inline comments. I notice there are a few failing tests too, let's address those next.

[mikachan]

Suggested change

	/* translators: %s: the value of the wp-config DB_CHARSET string. */
	/* translators: %s: the value of the wp-config DB_CHARSET string. */

[mikachan]

Just spotted that we have this DB_CHARSET reference on its own as well, which probably needs to be guarded too:

Suggested change

	DB_CHARSET
	defined( 'DB_CHARSET' ) ? DB_CHARSET : ''

[mikachan]

It looks like the $compat variable is shared across all three compatibility checks (PHP version, MySQL version, and now DB charset), but die() only renders it once. The existing check at lines 258-287 sets $compat to a version-mismatch message when either $php_compat or $mysql_compat is false. The new charset block then unconditionally re-assigns $compat whenever the charset check fails. So if someone has both an outdated PHP/MySQL version and an unsupported DB_CHARSET, the version error message is overwritten by the charset message before die() runs.

We should be able to address this by adding another guard before setting $compat here:

Suggested change

	$compat = sprintf(
	if ( $mysql_compat && $php_compat ) {
	$compat = sprintf(
	...

Or we could restructure this so each check has its own die(), and there's no shared variable to overwrite. What do you think?