Filter empty database parameters to prevent MySQL command failures

[Copilot]

MySQL commands fail when DB_HOST, DB_USER, DB_PASSWORD, or DB_CHARSET are defined as empty strings in wp-config.php. Empty values are passed as --host= --user= --default-character-set=, which MySQL rejects with errors like Character set '' is not a compiled character set.

Changes

• Filter empty parameters in DB_Command::run(): Added array_filter to strip empty strings and null values from the $required array before passing to MySQL commands
• Preserve valid edge cases: String '0' and integer 0 are kept (valid for ports/values)
• Add test coverage: New Behat scenario verifies empty DB_CHARSET doesn't generate invalid command-line arguments

Implementation

// Filter out empty string values to avoid passing empty parameters to MySQL commands
// which can cause errors like "Character set '' is not a compiled character set"
$required = array_filter(
    $required,
    static function ( $value ) {
        return null !== $value && '' !== $value;
    }
);

Applies to all commands using the run() method: check, optimize, repair, cli, query, export, import, etc.

Original prompt

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This section details on the original issue you should resolve

<issue_title>mysqlcheck: Character set '' is not a compiled character set</issue_title>
<issue_description>## Bug Report
When running commands related to db at hostinger, I get the following error.

mysqlcheck: Character set '' is not a compiled character set and is not specified in the '/usr/share/mysql/charsets/Index.xml' file
Unsupported character set:

Hostinger support said it's a bug with the wp-cli, and my debug shows the same..
Describe the current, buggy behavior

When running wp db check in any of my wp installs at hostinger, I get the following:

$ wp db check
mysqlcheck: Character set '' is not a compiled character set and is not specified in the '/usr/share/mysql/charsets/Index.xml' file
Unsupported character set:

With debug...

$ wp db check --debug
Debug (bootstrap): Processing bootstrap step: WP_CLI\Bootstrap\DeclareAbstractBaseCommand (0.014s)
Debug (bootstrap): Processing bootstrap step: WP_CLI\Bootstrap\IncludeFrameworkAutoloader (0.014s)
Debug (bootstrap): Processing bootstrap step: WP_CLI\Bootstrap\ConfigureRunner (0.014s)
Debug (bootstrap): Processing bootstrap step: WP_CLI\Bootstrap\IncludeRequestsAutoloader (0.014s)
Debug (bootstrap): Setting RequestsLibrary::$version to v2 (0.014s)
Debug (bootstrap): Setting RequestsLibrary::$source to wp-core (0.014s)
Debug (bootstrap): Setting RequestsLibrary::$class_name to \WpOrg\Requests\Requests (0.014s)
Debug (bootstrap): Processing bootstrap step: WP_CLI\Bootstrap\InitializeColorization (0.014s)
Debug (bootstrap): Processing bootstrap step: WP_CLI\Bootstrap\InitializeLogger (0.014s)
Debug (bootstrap): Processing bootstrap step: WP_CLI\Bootstrap\DefineProtectedCommands (0.014s)
Debug (bootstrap): Processing bootstrap step: WP_CLI\Bootstrap\LoadExecCommand (0.014s)
Debug (bootstrap): Processing bootstrap step: WP_CLI\Bootstrap\LoadRequiredCommand (0.015s)
Debug (bootstrap): Processing bootstrap step: WP_CLI\Bootstrap\IncludePackageAutoloader (0.015s)
Debug (bootstrap): Processing bootstrap step: WP_CLI\Bootstrap\IncludeFallbackAutoloader (0.015s)
Debug (bootstrap): Fallback autoloader paths: phar://wp-cli.phar/vendor/autoload.php (0.015s)
Debug (bootstrap): Loading detected autoloader: phar://wp-cli.phar/vendor/autoload.php (0.015s)
Debug (bootstrap): Attaching command 'config edit' to hook before_wp_load (0.022s)
Debug (bootstrap): Attaching command 'config path' to hook before_wp_load (0.022s)
Debug (bootstrap): Attaching command 'config list' to hook before_wp_load (0.022s)
Debug (bootstrap): Attaching command 'config get' to hook before_wp_load (0.022s)
Debug (bootstrap): Attaching command 'config is-true' to hook before_wp_load (0.022s)
Debug (bootstrap): Attaching command 'config set' to hook before_wp_load (0.022s)
Debug (bootstrap): Attaching command 'config delete' to hook before_wp_load (0.022s)
Debug (bootstrap): Attaching command 'config has' to hook before_wp_load (0.022s)
Debug (bootstrap): Attaching command 'config shuffle-salts' to hook before_wp_load (0.022s)
Debug (commands): Adding command: config (0.022s)
Debug (bootstrap): Attaching command 'core download' to hook before_wp_load (0.024s)
Debug (bootstrap): Attaching command 'core version' to hook before_wp_load (0.024s)
Debug (commands): Adding command: core (0.024s)
Debug (bootstrap): Attaching command 'eval' to hook before_wp_load (0.024s)
Debug (commands): Adding command: eval (0.025s)
Debug (bootstrap): Attaching command 'eval-file' to hook before_wp_load (0.025s)
Debug (commands): Adding command: eval-file (0.025s)
Debug (commands): Adding command: cache (0.025s)
Debug (commands): Adding command: transient (0.026s)
Debug (bootstrap): Attaching command 'core verify-checksums' to hook before_wp_load (0.027s)
Debug (commands): Adding command: verify-checksums in core Namespace (0.027s)
Debug (commands): Adding command: plugin (0.027s)
Debug (commands): Adding command: verify-checksums in plugin Namespace (0.027s)
Debug (commands): Adding command: cron (0.028s)
Debug (commands): Adding command: event in cron Namespace (0.028s)
Debug (commands): Adding command: schedule in cron Namespace (0.028s)
Debug (bootstrap): Attaching command 'db' to hook after_wp_config_load (0.03s)
Debug (bootstrap): Attaching command 'db clean' to hook after_wp_load (0.031s)
Debug (bootstrap): Attaching command 'db tables' to hook after_wp_load (0.031s)
Debug (bootstrap): Attaching command 'db size' to hook after_wp_load (0.031s)
Debug (bootstrap): Attaching command 'db prefix' to hook after_wp_load (0.031s)
Debug (bootstrap): Attaching command 'db search' to hook after_wp_load (0.031s)
Debug (bootstrap): Attaching command 'db columns' to hook after_wp_load (0.031s)
Debug (commands): Adding command: db (0.032s)
Debug (commands): Adding command: embed (0.032s)
Debug (commands): Adding command: fetch in embed Namespace (0.032s)
Debug (commands...

• Fixes mysqlcheck: Character set '' is not a compiled character set #268

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