source: node_modules/highlight.js/lib/languages/yaml.js

/*
Language: YAML
Description: Yet Another Markdown Language
Author: Stefan Wienert <stwienert@gmail.com>
Contributors: Carl Baxter <carl@cbax.tech>
Requires: ruby.js
Website: https://yaml.org
Category: common, config
*/
function yaml(hljs) {
  var LITERALS = 'true false yes no null';

  // YAML spec allows non-reserved URI characters in tags.
  var URI_CHARACTERS = '[\\w#;/?:@&=+$,.~*\'()[\\]]+';

  // Define keys as starting with a word character
  // ...containing word chars, spaces, colons, forward-slashes, hyphens and periods
  // ...and ending with a colon followed immediately by a space, tab or newline.
  // The YAML spec allows for much more than this, but this covers most use-cases.
  var KEY = {
    className: 'attr',
    variants: [
      { begin: '\\w[\\w :\\/.-]*:(?=[ \t]|$)' },
      { begin: '"\\w[\\w :\\/.-]*":(?=[ \t]|$)' }, // double quoted keys
      { begin: '\'\\w[\\w :\\/.-]*\':(?=[ \t]|$)' } // single quoted keys
    ]
  };

  var TEMPLATE_VARIABLES = {
    className: 'template-variable',
    variants: [
      { begin: /\{\{/, end: /\}\}/ }, // jinja templates Ansible
      { begin: /%\{/, end: /\}/ } // Ruby i18n
    ]
  };
  var STRING = {
    className: 'string',
    relevance: 0,
    variants: [
      { begin: /'/, end: /'/ },
      { begin: /"/, end: /"/ },
      { begin: /\S+/ }
    ],
    contains: [
      hljs.BACKSLASH_ESCAPE,
      TEMPLATE_VARIABLES
    ]
  };

  // Strings inside of value containers (objects) can't contain braces,
  // brackets, or commas
  var CONTAINER_STRING = hljs.inherit(STRING, {
    variants: [
      { begin: /'/, end: /'/ },
      { begin: /"/, end: /"/ },
      { begin: /[^\s,{}[\]]+/ }
    ]
  });

  var DATE_RE = '[0-9]{4}(-[0-9][0-9]){0,2}';
  var TIME_RE = '([Tt \\t][0-9][0-9]?(:[0-9][0-9]){2})?';
  var FRACTION_RE = '(\\.[0-9]*)?';
  var ZONE_RE = '([ \\t])*(Z|[-+][0-9][0-9]?(:[0-9][0-9])?)?';
  var TIMESTAMP = {
    className: 'number',
    begin: '\\b' + DATE_RE + TIME_RE + FRACTION_RE + ZONE_RE + '\\b'
  };

  var VALUE_CONTAINER = {
    end: ',',
    endsWithParent: true,
    excludeEnd: true,
    keywords: LITERALS,
    relevance: 0
  };
  var OBJECT = {
    begin: /\{/,
    end: /\}/,
    contains: [VALUE_CONTAINER],
    illegal: '\\n',
    relevance: 0
  };
  var ARRAY = {
    begin: '\\[',
    end: '\\]',
    contains: [VALUE_CONTAINER],
    illegal: '\\n',
    relevance: 0
  };

  var MODES = [
    KEY,
    {
      className: 'meta',
      begin: '^---\\s*$',
      relevance: 10
    },
    { // multi line string
      // Blocks start with a | or > followed by a newline
      //
      // Indentation of subsequent lines must be the same to
      // be considered part of the block
      className: 'string',
      begin: '[\\|>]([1-9]?[+-])?[ ]*\\n( +)[^ ][^\\n]*\\n(\\2[^\\n]+\\n?)*'
    },
    { // Ruby/Rails erb
      begin: '<%[%=-]?',
      end: '[%-]?%>',
      subLanguage: 'ruby',
      excludeBegin: true,
      excludeEnd: true,
      relevance: 0
    },
    { // named tags
      className: 'type',
      begin: '!\\w+!' + URI_CHARACTERS
    },
    // https://yaml.org/spec/1.2/spec.html#id2784064
    { // verbatim tags
      className: 'type',
      begin: '!<' + URI_CHARACTERS + ">"
    },
    { // primary tags
      className: 'type',
      begin: '!' + URI_CHARACTERS
    },
    { // secondary tags
      className: 'type',
      begin: '!!' + URI_CHARACTERS
    },
    { // fragment id &ref
      className: 'meta',
      begin: '&' + hljs.UNDERSCORE_IDENT_RE + '$'
    },
    { // fragment reference *ref
      className: 'meta',
      begin: '\\*' + hljs.UNDERSCORE_IDENT_RE + '$'
    },
    { // array listing
      className: 'bullet',
      // TODO: remove |$ hack when we have proper look-ahead support
      begin: '-(?=[ ]|$)',
      relevance: 0
    },
    hljs.HASH_COMMENT_MODE,
    {
      beginKeywords: LITERALS,
      keywords: { literal: LITERALS }
    },
    TIMESTAMP,
    // numbers are any valid C-style number that
    // sit isolated from other words
    {
      className: 'number',
      begin: hljs.C_NUMBER_RE + '\\b',
      relevance: 0
    },
    OBJECT,
    ARRAY,
    STRING
  ];

  var VALUE_MODES = [...MODES];
  VALUE_MODES.pop();
  VALUE_MODES.push(CONTAINER_STRING);
  VALUE_CONTAINER.contains = VALUE_MODES;

  return {
    name: 'YAML',
    case_insensitive: true,
    aliases: [ 'yml' ],
    contains: MODES
  };
}

module.exports = yaml;