Make this work like a normal WP plugin

[mattbucci]

Because this plugin has to start so early in the app lifecycle it requires that we copy db.php to wp-content but this process is weird and cumbersome.

It would be great if this plugin could somehow act like a standard WordPress plugin which can be installed and activated

[mattbucci]

https://wordpress.org/plugins/sqlite-database-integration/ can be used as reference.

The basic idea is that on activation we should copy the file db.php

Here's their code for reference

<?php
/**
 * Handle the SQLite activation.
 *
 * @since 1.0.0
 * @package wp-sqlite-integration
 */

/**
 * Redirect to the plugin's admin screen on activation.
 *
 * @since 1.0.0
 *
 * @param string $plugin The plugin basename.
 */
function sqlite_plugin_activation_redirect( $plugin ) {
    if ( plugin_basename( SQLITE_MAIN_FILE ) === $plugin ) {
        wp_redirect( admin_url( 'options-general.php?page=sqlite-integration' ) );
        exit;
    }
}
add_action( 'activated_plugin', 'sqlite_plugin_activation_redirect' );

/**
 * Check the URL to ensure we're on the plugin page,
 * the user has clicked the button to install SQLite,
 * and the nonce is valid.
 * If the above conditions are met, run the sqlite_plugin_copy_db_file() function,
 * and redirect to the install screen.
 *
 * @since 1.0.0
 */
function sqlite_activation() {
    global $current_screen;
    if ( isset( $current_screen->base ) && 'settings_page_sqlite-integration' === $current_screen->base ) {
        return;
    }
    if ( isset( $_GET['confirm-install'] ) && wp_verify_nonce( $_GET['_wpnonce'], 'sqlite-install' ) ) {

        // Handle upgrading from the performance-lab plugin.
        if ( isset( $_GET['upgrade-from-pl'] ) ) {
            global $wp_filesystem;
            require_once ABSPATH . '/wp-admin/includes/file.php';
            // Delete the previous db.php file.
            $wp_filesystem->delete( WP_CONTENT_DIR . '/db.php' );
            // Deactivate the performance-lab SQLite module.
            $pl_option_name = defined( 'PERFLAB_MODULES_SETTING' ) ? PERFLAB_MODULES_SETTING : 'perflab_modules_settings';
            $pl_option      = get_option( $pl_option_name, array() );
            unset( $pl_option['database/sqlite'] );
            update_option( $pl_option_name, $pl_option );
        }
        sqlite_plugin_copy_db_file();
        // WordPress will automatically redirect to the install screen here.
        wp_redirect( admin_url() );
        exit;
    }
}
add_action( 'admin_init', 'sqlite_activation' );

// Flush the cache at the last moment before the redirect.
add_filter(
    'x_redirect_by',
    function ( $result ) {
        wp_cache_flush();
        return $result;
    },
    PHP_INT_MAX,
    1
);

/**
 * Add the db.php file in wp-content.
 *
 * When the plugin gets merged in wp-core, this is not to be ported.
 */
function sqlite_plugin_copy_db_file() {
    // Bail early if the SQLite3 class does not exist.
    if ( ! class_exists( 'SQLite3' ) ) {
        return;
    }

    $destination = WP_CONTENT_DIR . '/db.php';

    // Place database drop-in if not present yet, except in case there is
    // another database drop-in present already.
    if ( ! defined( 'SQLITE_DB_DROPIN_VERSION' ) && ! file_exists( $destination ) ) {
        // Init the filesystem to allow copying the file.
        global $wp_filesystem;

        require_once ABSPATH . '/wp-admin/includes/file.php';

        // Init the filesystem if needed, then copy the file, replacing contents as needed.
        if ( ( $wp_filesystem || WP_Filesystem() ) && $wp_filesystem->touch( $destination ) ) {

            // Get the db.copy.php file contents, replace placeholders and write it to the destination.
            $file_contents = str_replace(
                array(
                    '{SQLITE_IMPLEMENTATION_FOLDER_PATH}',
                    '{SQLITE_PLUGIN}',
                ),
                array(
                    __DIR__,
                    str_replace( WP_PLUGIN_DIR . '/', '', SQLITE_MAIN_FILE ),
                ),
                file_get_contents( __DIR__ . '/db.copy' )
            );

            $wp_filesystem->put_contents( $destination, $file_contents );
        }
    }
}

[mattbucci]

Here's what the deactivate code looks like

<?php
/**
 * Handle the SQLite deactivation.
 *
 * @since 1.0.0
 * @package wp-sqlite-integration
 */

/**
 * Delete the db.php file in wp-content.
 *
 * When the plugin gets merged in wp-core, this is not to be ported.
 */
function sqlite_plugin_remove_db_file() {
    if ( ! defined( 'SQLITE_DB_DROPIN_VERSION' ) || ! file_exists( WP_CONTENT_DIR . '/db.php' ) ) {
        return;
    }

    global $wp_filesystem;

    require_once ABSPATH . '/wp-admin/includes/file.php';

    // Init the filesystem if needed, then delete custom drop-in.
    if ( $wp_filesystem || WP_Filesystem() ) {
        // Flush any persistent cache.
        wp_cache_flush();
        // Delete the drop-in.
        $wp_filesystem->delete( WP_CONTENT_DIR . '/db.php' );
        // Flush the cache again to mitigate a possible race condition.
        wp_cache_flush();
    }

    // Run an action on `shutdown`, to deactivate the option in the MySQL database.
    add_action(
        'shutdown',
        function() {
            global $table_prefix;

            // Get credentials for the MySQL database.
            $dbuser     = defined( 'DB_USER' ) ? DB_USER : '';
            $dbpassword = defined( 'DB_PASSWORD' ) ? DB_PASSWORD : '';
            $dbname     = defined( 'DB_NAME' ) ? DB_NAME : '';
            $dbhost     = defined( 'DB_HOST' ) ? DB_HOST : '';

            // Init a connection to the MySQL database.
            $wpdb_mysql = new wpdb( $dbuser, $dbpassword, $dbname, $dbhost );
            $wpdb_mysql->set_prefix( $table_prefix );

            // Get the perflab options, remove the database/sqlite module and update the option.
            $row = $wpdb_mysql->get_row( $wpdb_mysql->prepare( "SELECT option_value FROM $wpdb_mysql->options WHERE option_name = %s LIMIT 1", 'active_plugins' ) );
            if ( is_object( $row ) ) {
                $value = maybe_unserialize( $row->option_value );
                if ( is_array( $value ) ) {
                    $value_flipped = array_flip( $value );
                    $items         = array_reverse( explode( DIRECTORY_SEPARATOR, SQLITE_MAIN_FILE ) );
                    $item          = $items[1] . DIRECTORY_SEPARATOR . $items[0];
                    unset( $value_flipped[ $item ] );
                    $value = array_flip( $value_flipped );
                    $wpdb_mysql->update( $wpdb_mysql->options, array( 'option_value' => maybe_serialize( $value ) ), array( 'option_name' => 'active_plugins' ) );
                }
            }
        },
        PHP_INT_MAX
    );
    // Flush any persistent cache.
    wp_cache_flush();
}
register_deactivation_hook( SQLITE_MAIN_FILE, 'sqlite_plugin_remove_db_file' ); // Remove db.php file on plugin deactivation.