img-redundant-alt.js

/**
 * @fileoverview Enforce img alt attribute does not have the word image, picture, or photo.
 * @author Ethan Cohen
 */

// ----------------------------------------------------------------------------
// Rule Definition
// ----------------------------------------------------------------------------

import { getProp, getLiteralPropValue } from 'jsx-ast-utils';
import includes from 'array-includes';
import stringIncludes from 'string.prototype.includes';
import safeRegexTest from 'safe-regex-test';
import { generateObjSchema, arraySchema } from '../util/schemas';
import getElementType from '../util/getElementType';
import isHiddenFromScreenReader from '../util/isHiddenFromScreenReader';

const REDUNDANT_WORDS = [
  'image',
  'photo',
  'picture',
];

const errorMessage = 'Redundant alt attribute. Screen-readers already announce `img` tags as an image. You don’t need to use the words `image`, `photo,` or `picture` (or any specified custom words) in the alt prop.';

const schema = generateObjSchema({
  components: arraySchema,
  words: arraySchema,
});

const isASCII = safeRegexTest(/[\x20-\x7F]+/);

function containsRedundantWord(value, redundantWords) {
  const lowercaseRedundantWords = redundantWords.map((redundantWord) => redundantWord.toLowerCase());

  if (isASCII(value)) {
    return value.split(/\s+/).some((valueWord) => includes(lowercaseRedundantWords, valueWord.toLowerCase()));
  }
  return lowercaseRedundantWords.some((redundantWord) => stringIncludes(value.toLowerCase(), redundantWord));
}

export default {
  meta: {
    docs: {
      url: 'https://github.com/jsx-eslint/eslint-plugin-jsx-a11y/tree/HEAD/docs/rules/img-redundant-alt.md',
      description: 'Enforce `<img>` alt prop does not contain the word "image", "picture", or "photo".',
    },
    schema: [schema],
  },

  create: (context) => {
    const elementType = getElementType(context);
    return {
      JSXOpeningElement: (node) => {
        const options = context.options[0] || {};
        const componentOptions = options.components || [];
        const typesToValidate = ['img'].concat(componentOptions);
        const nodeType = elementType(node);

        // Only check 'label' elements and custom types.
        if (typesToValidate.indexOf(nodeType) === -1) {
          return;
        }

        const altProp = getProp(node.attributes, 'alt');
        // Return if alt prop is not present.
        if (altProp === undefined) {
          return;
        }

        const value = getLiteralPropValue(altProp);
        const isVisible = isHiddenFromScreenReader(nodeType, node.attributes) === false;

        const {
          words = [],
        } = options;
        const redundantWords = REDUNDANT_WORDS.concat(words);

        if (typeof value === 'string' && isVisible) {
          const hasRedundancy = containsRedundantWord(value, redundantWords);

          if (hasRedundancy === true) {
            context.report({
              node,
              message: errorMessage,
            });
          }
        }
      },
    };
  },
};