Source

File: wp-admin/includes/theme.php

function delete_theme( $stylesheet, $redirect = '' ) {
	global $wp_filesystem;

	if ( empty( $stylesheet ) ) {
		return false;
	}

	if ( empty( $redirect ) ) {
		$redirect = wp_nonce_url( 'themes.php?action=delete&stylesheet=' . urlencode( $stylesheet ), 'delete-theme_' . $stylesheet );
	}

	ob_start();
	$credentials = request_filesystem_credentials( $redirect );
	$data        = ob_get_clean();

	if ( false === $credentials ) {
		if ( ! empty( $data ) ) {
			require_once ABSPATH . 'wp-admin/admin-header.php';
			echo $data;
			require_once ABSPATH . 'wp-admin/admin-footer.php';
			exit;
		}
		return;
	}

	if ( ! WP_Filesystem( $credentials ) ) {
		ob_start();
		// Failed to connect. Error and request again.
		request_filesystem_credentials( $redirect, '', true );
		$data = ob_get_clean();

		if ( ! empty( $data ) ) {
			require_once ABSPATH . 'wp-admin/admin-header.php';
			echo $data;
			require_once ABSPATH . 'wp-admin/admin-footer.php';
			exit;
		}
		return;
	}

	if ( ! is_object( $wp_filesystem ) ) {
		return new WP_Error( 'fs_unavailable', __( 'Could not access filesystem.' ) );
	}

	if ( is_wp_error( $wp_filesystem->errors ) && $wp_filesystem->errors->has_errors() ) {
		return new WP_Error( 'fs_error', __( 'Filesystem error.' ), $wp_filesystem->errors );
	}

	// Get the base plugin folder.
	$themes_dir = $wp_filesystem->wp_themes_dir();
	if ( empty( $themes_dir ) ) {
		return new WP_Error( 'fs_no_themes_dir', __( 'Unable to locate WordPress theme directory.' ) );
	}

	$themes_dir = trailingslashit( $themes_dir );
	$theme_dir  = trailingslashit( $themes_dir . $stylesheet );
	$deleted    = $wp_filesystem->delete( $theme_dir, true );

	if ( ! $deleted ) {
		return new WP_Error(
			'could_not_remove_theme',
			/* translators: %s: Theme name. */
			sprintf( __( 'Could not fully remove the theme %s.' ), $stylesheet )
		);
	}

	$theme_translations = wp_get_installed_translations( 'themes' );

	// Remove language files, silently.
	if ( ! empty( $theme_translations[ $stylesheet ] ) ) {
		$translations = $theme_translations[ $stylesheet ];

		foreach ( $translations as $translation => $data ) {
			$wp_filesystem->delete( WP_LANG_DIR . '/themes/' . $stylesheet . '-' . $translation . '.po' );
			$wp_filesystem->delete( WP_LANG_DIR . '/themes/' . $stylesheet . '-' . $translation . '.mo' );

			$json_translation_files = glob( WP_LANG_DIR . '/themes/' . $stylesheet . '-' . $translation . '-*.json' );
			if ( $json_translation_files ) {
				array_map( array( $wp_filesystem, 'delete' ), $json_translation_files );
			}
		}
	}

	// Remove the theme from allowed themes on the network.
	if ( is_multisite() ) {
		WP_Theme::network_disable_theme( $stylesheet );
	}

	// Force refresh of theme update information.
	delete_site_transient( 'update_themes' );

	return true;
}