WP_REST_Plugins_Controller::is_filesystem_available()
Determine if the endpoints are available.
Description
Only the ‘Direct’ filesystem transport, and SSH/FTP when credentials are stored are supported at present.
Return
(true|WP_Error) True if filesystem is available, WP_Error otherwise.
Source
File: wp-includes/rest-api/endpoints/class-wp-rest-plugins-controller.php
protected function is_filesystem_available() {
		$filesystem_method = get_filesystem_method();
		if ( 'direct' === $filesystem_method ) {
			return true;
		}
		ob_start();
		$filesystem_credentials_are_stored = request_filesystem_credentials( self_admin_url() );
		ob_end_clean();
		if ( $filesystem_credentials_are_stored ) {
			return true;
		}
		return new WP_Error( 'fs_unavailable', __( 'The filesystem is currently unavailable for managing plugins.' ), array( 'status' => 500 ) );
	}  Changelog
| Version | Description | 
|---|---|
| 5.5.0 | Introduced. | 
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Licensed under the GNU GPLv2+ License.
    https://developer.wordpress.org/reference/classes/wp_rest_plugins_controller/is_filesystem_available