material-components_material-web/sass/ext/_assert.scss

//
// Copyright 2025 Google LLC
// SPDX-License-Identifier: Apache-2.0
//

// Utility assert functions that throw errors.

// go/keep-sorted start by_regex='(.+) prefix_order=sass:
@use 'sass:meta';
@use 'throw';
@use 'type';
// go/keep-sorted end

/// Asserts that the argument is a specific type. If it is, the argument is
/// returned, otherwise an error is thrown.
///
/// @example scss
///   @mixin multiply($a, $b) {
///     $a: assert.is-type($a, 'number');
///     $b: assert.is-type($b, 'number');
///     @return $a * $b;
///   }
///
///   @function is-empty($value) {
///     $value: assert.is-type(
///       $value,
///       'list|map|null',
///       $message: '$value must be a list, map, or null',
///       $source: 'is-empty'
///     );
///     @return $value and list.length($value) == 0;
///   }
///
/// @param {*} $arg - The argument to check.
/// @param {string} $type - The string type to assert the argument matches.
///     Multiple types may be separated by '|'.
/// @param {string} $message - Optional custom error message.
/// @param {string} $source - Optional source of the error message.
/// @return {*} The argument if it matches the type string.
/// @throw Error if the argument does not match the type string.
@function is-type(
  $arg,
  $type,
  $message: 'Argument must be type #{meta.inspect($type)}. $arg: #{meta.inspect($arg)}',
  $source: 'assert.is-type'
) {
  @if type.matches($arg, $type) {
    @return $arg;
  }
  @return throw.error($message, $source);
}

/// Asserts that the argument is not a specific type. The argument is returned
/// if it does not match. An error is thrown if the argument matches the type.
///
/// @example scss
///   @function get-strict($map, $key) {
///     @return assert.not-type(
///       map.get($map, $key),
///       'null',
///       $message: 'Key must be in the map'
///     );
///   }
///
/// @param {*} $arg - The argument to check.
/// @param {string} $type - The string type to assert the argument does not
///     match. Multiple types may be separated by '|'.
/// @param {string} $message - Optional custom error message.
/// @param {string} $source - Optional source of the error message.
/// @return {*} The argument if it does not match the type string.
/// @throw Error if the argument matches the type string.
@function not-type(
  $arg,
  $type,
  $message: 'Argument may not be type #{meta.inspect($type)}. $arg: #{meta.inspect($arg)}',
  $source: 'assert.not-type'
) {
  @if type.matches($arg, $type) {
    @return throw.error($message, $source);
  }
  @return $arg;
}