unsafe.js

/**
 * @typedef {import('./types.js').ConstructName} ConstructName
 * @typedef {import('./types.js').Unsafe} Unsafe
 */

/**
 * List of constructs that occur in phrasing (paragraphs, headings), but cannot
 * contain things like attention (emphasis, strong), images, or links.
 * So they sort of cancel each other out.
 * Note: could use a better name.
 *
 * @type {Array<ConstructName>}
 */
const fullPhrasingSpans = [
  'autolink',
  'destinationLiteral',
  'destinationRaw',
  'reference',
  'titleQuote',
  'titleApostrophe'
]

/** @type {Array<Unsafe>} */
export const unsafe = [
  {character: '\t', after: '[\\r\\n]', inConstruct: 'phrasing'},
  {character: '\t', before: '[\\r\\n]', inConstruct: 'phrasing'},
  {
    character: '\t',
    inConstruct: ['codeFencedLangGraveAccent', 'codeFencedLangTilde']
  },
  {
    character: '\r',
    inConstruct: [
      'codeFencedLangGraveAccent',
      'codeFencedLangTilde',
      'codeFencedMetaGraveAccent',
      'codeFencedMetaTilde',
      'destinationLiteral',
      'headingAtx'
    ]
  },
  {
    character: '\n',
    inConstruct: [
      'codeFencedLangGraveAccent',
      'codeFencedLangTilde',
      'codeFencedMetaGraveAccent',
      'codeFencedMetaTilde',
      'destinationLiteral',
      'headingAtx'
    ]
  },
  {character: ' ', after: '[\\r\\n]', inConstruct: 'phrasing'},
  {character: ' ', before: '[\\r\\n]', inConstruct: 'phrasing'},
  {
    character: ' ',
    inConstruct: ['codeFencedLangGraveAccent', 'codeFencedLangTilde']
  },
  // An exclamation mark can start an image, if it is followed by a link or
  // a link reference.
  {
    character: '!',
    after: '\\[',
    inConstruct: 'phrasing',
    notInConstruct: fullPhrasingSpans
  },
  // A quote can break out of a title.
  {character: '"', inConstruct: 'titleQuote'},
  // A number sign could start an ATX heading if it starts a line.
  {atBreak: true, character: '#'},
  {character: '#', inConstruct: 'headingAtx', after: '(?:[\r\n]|$)'},
  // Dollar sign and percentage are not used in markdown.
  // An ampersand could start a character reference.
  {character: '&', after: '[#A-Za-z]', inConstruct: 'phrasing'},
  // An apostrophe can break out of a title.
  {character: "'", inConstruct: 'titleApostrophe'},
  // A left paren could break out of a destination raw.
  {character: '(', inConstruct: 'destinationRaw'},
  // A left paren followed by `]` could make something into a link or image.
  {
    before: '\\]',
    character: '(',
    inConstruct: 'phrasing',
    notInConstruct: fullPhrasingSpans
  },
  // A right paren could start a list item or break out of a destination
  // raw.
  {atBreak: true, before: '\\d+', character: ')'},
  {character: ')', inConstruct: 'destinationRaw'},
  // An asterisk can start thematic breaks, list items, emphasis, strong.
  {atBreak: true, character: '*', after: '(?:[ \t\r\n*])'},
  {character: '*', inConstruct: 'phrasing', notInConstruct: fullPhrasingSpans},
  // A plus sign could start a list item.
  {atBreak: true, character: '+', after: '(?:[ \t\r\n])'},
  // A dash can start thematic breaks, list items, and setext heading
  // underlines.
  {atBreak: true, character: '-', after: '(?:[ \t\r\n-])'},
  // A dot could start a list item.
  {atBreak: true, before: '\\d+', character: '.', after: '(?:[ \t\r\n]|$)'},
  // Slash, colon, and semicolon are not used in markdown for constructs.
  // A less than can start html (flow or text) or an autolink.
  // HTML could start with an exclamation mark (declaration, cdata, comment),
  // slash (closing tag), question mark (instruction), or a letter (tag).
  // An autolink also starts with a letter.
  // Finally, it could break out of a destination literal.
  {atBreak: true, character: '<', after: '[!/?A-Za-z]'},
  {
    character: '<',
    after: '[!/?A-Za-z]',
    inConstruct: 'phrasing',
    notInConstruct: fullPhrasingSpans
  },
  {character: '<', inConstruct: 'destinationLiteral'},
  // An equals to can start setext heading underlines.
  {atBreak: true, character: '='},
  // A greater than can start block quotes and it can break out of a
  // destination literal.
  {atBreak: true, character: '>'},
  {character: '>', inConstruct: 'destinationLiteral'},
  // Question mark and at sign are not used in markdown for constructs.
  // A left bracket can start definitions, references, labels,
  {atBreak: true, character: '['},
  {character: '[', inConstruct: 'phrasing', notInConstruct: fullPhrasingSpans},
  {character: '[', inConstruct: ['label', 'reference']},
  // A backslash can start an escape (when followed by punctuation) or a
  // hard break (when followed by an eol).
  // Note: typical escapes are handled in `safe`!
  {character: '\\', after: '[\\r\\n]', inConstruct: 'phrasing'},
  // A right bracket can exit labels.
  {character: ']', inConstruct: ['label', 'reference']},
  // Caret is not used in markdown for constructs.
  // An underscore can start emphasis, strong, or a thematic break.
  {atBreak: true, character: '_'},
  {character: '_', inConstruct: 'phrasing', notInConstruct: fullPhrasingSpans},
  // A grave accent can start code (fenced or text), or it can break out of
  // a grave accent code fence.
  {atBreak: true, character: '`'},
  {
    character: '`',
    inConstruct: ['codeFencedLangGraveAccent', 'codeFencedMetaGraveAccent']
  },
  {character: '`', inConstruct: 'phrasing', notInConstruct: fullPhrasingSpans},
  // Left brace, vertical bar, right brace are not used in markdown for
  // constructs.
  // A tilde can start code (fenced).
  {atBreak: true, character: '~'}
]