gatsby-remark-prismjs/load-prism-language-extension.js

Adds syntax highlighting to code blocks at build time using PrismJS

"use strict";

const Prism = require(`prismjs`);
const loadPrismLanguage = require(`./load-prism-language`);
const replaceStringWithRegex = require(`./replace-string-with-regexp`);
module.exports = languageExtensions => {
  // Create array of languageExtensions (if input is object)
  languageExtensions = [].concat(languageExtensions);
  languageExtensions.forEach(l => {
    loadLanguageExtension(l);
  });
};
const loadLanguageExtension = languageExtension => {
  if (!isObjectAndNotArray(languageExtension)) {
    throw new Error(`A languageExtension needs to be defined as an object. Given config is not valid: ${JSON.stringify(languageExtension)}`);
  }
  if (!containsMandatoryProperties(languageExtension)) {
    throw new Error(`A languageExtension needs to contain 'language' and 'extend' or both and a 'definition'. Given config is not valid: ${JSON.stringify(languageExtension)}`);
  }

  // If only 'extend' property is given, we extend the given extend language.
  if (!languageExtension.language) {
    languageExtension.language = languageExtension.extend;
  }

  // To allow RegEx as 'string' in the config, we replace all strings with a regex object.
  if (languageExtension.definition) {
    languageExtension.definition = replaceStringWithRegex(languageExtension.definition);
  }

  // If 'extend' property is given we start from that language, otherwise we add a language from scratch.
  if (!languageExtension.extend) {
    Prism.languages[languageExtension.language] = languageExtension.definition;
  } else {
    // Loads language if not already loaded.
    loadPrismLanguage(languageExtension.extend);
    Prism.languages[languageExtension.language] = Prism.languages.extend(languageExtension.extend, languageExtension.definition);
  }
  if (languageExtension.hasOwnProperty(`insertBefore`)) {
    // To allow RegEx as 'string' in the config, we replace all strings with a regex object.
    languageExtension.insertBefore = replaceStringWithRegex(languageExtension.insertBefore);
    Object.entries(languageExtension.insertBefore).forEach(([key, value]) => {
      Prism.languages.insertBefore(languageExtension.language, key, value);
    });
  }
};
const isObjectAndNotArray = extension =>
// Array is an Object in javascript
!Array.isArray(extension) && typeof extension === `object`;
const containsMandatoryProperties = languageExtension => {
  // 'language' or 'extend' is mandatory
  if (!(languageExtension.language || languageExtension.extend)) {
    return false;
  }

  // 'definition' or 'insertBefore' is mandatory
  if (!(languageExtension.definition || languageExtension.insertBefore)) {
    return false;
  }

  // 'insertBefore' is not possible without 'extend' or 'definition'. There is nothing to insert before then.
  if (languageExtension.insertBefore && !(languageExtension.definition || languageExtension.extend)) {
    return false;
  }
  return true;
};