grammar.js

// TODO: support `tag(attr='hello' + goodbye)`
// TODO: support multiple levels of function calls in pug js attrs: `tag(attr=true.call(false.toString()))`
//       I think something a bit like:
//         value = ($) => seq(/.*/, optional(seq('(', $.value, ')')))
//       where the content of brackets is another instance of the same node. Does treesitter even support this?
//       The entire node will have to be aliased as $.javascript, this will just make sure no pug is matched too.
// TODO: don't break if there are singular { or # in content
// TODO: support #[p(prop)] nested pug syntax
// TODO: support Angular's weird `let x as first; let y of items` template directive syntax.
//       documentation here: https://angular.io/guide/structural-directives#structural-directive-syntax-reference
//       Currently, it is just parsed as $.javascript, but this is not valid javascript, so parsing is broken,
//       but doesn't break any of the pug syntax tree.
// TODO: rework regexes. There are too many different regexes that all handle different special cases.
module.exports = grammar({
  name: "pug",
  externals: ($) => [$._newline, $._indent, $._dedent],
  rules: {
    source_file: ($) => repeat(
      choice(
        $.conditional,
        $.comment,
        $.script_block,
        $.tag,
        $.doctype,
        $.unbuffered_code,
        $.buffered_code,
        $.unescaped_buffered_code,
        $.case,
        $.pipe,
        $.filter,
        $.block_definition,
        $.block_append,
        $.block_prepend,
        $.extends,
        $.mixin_definition,
        $.mixin_use,
        $.each,
        $.while,
        $.include,
      ),
    ),
    doctype: ($) =>
      seq(
        "doctype", 
        alias(
          choice(
            "html", 
            "strict", 
            "xml", 
            "transitional", 
            "frameset", 
            "1.1", 
            "basic", 
            "mobile", 
            "plist"
          ), 
          $.doctype_name
        )
      ),
    pipe: ($) =>
      seq("|", optional($._content_or_javascript), $._newline),

    include: ($) =>
      seq(
        alias('include', $.keyword),
        optional($.filter),
        alias(/[^\n]+/, $.filename),
      ),

    while: ($) =>
      seq(
        alias('while', $.keyword),
        $.iteration_iterator,
        $._newline,
        $.children,
      ),

    _each_js: ($) =>
      alias(/[\w_]+/, $.javascript),

    iteration_variable: ($) =>
      seq(
        $._each_js,
        optional(
          seq(
            ',',
            $._each_js,
          ),
        ),
      ),

    iteration_iterator: ($) =>
      alias(/[^\n]+/, $.javascript),

    _each_else: ($) =>
      seq(
        alias('else', $.keyword),
        $._newline,
        $.children,
      ),

    each: ($) =>
      prec.right(
        seq(
          alias(choice('each', 'for'), $.keyword),
          $.iteration_variable,
          alias('in', $.keyword),
          $.iteration_iterator,
          $._newline,
          $.children,
          alias(
            optional(
              $._each_else
            ),
            $.else
          ),
        ),
      ),

    mixin_use: ($) =>
      seq(
        '+',
        alias($.tag_name, $.mixin_name),
        optional(
          seq(
            '(',
            optional(
              seq(
                repeat(
                  seq(
                    alias($._pug_attributes, $.attribute),
                    ',',
                  )
                ),
                alias($._pug_attributes, $.attribute),
              )
            ),
            ')',
          ),
        ),
      ),
    mixin_definition: ($) =>
      seq(
        alias('mixin', $.keyword),
        alias($.tag_name, $.mixin_name),
        optional($.mixin_attributes),
        $._newline,
        $.children,
      ),
    mixin_attributes: ($) =>
      seq(
        '(',
        optional(
          seq(
            repeat(
              seq(
                alias(/\w+/, $.attribute_name),
                ',',
              )
            ),
            alias(/\w+/, $.attribute_name),
          )
        ),
        ')',
      ),

    _block_content: ($) =>
      prec.left(
        seq(
          alias($.tag_name, $.block_name),
          optional(
            seq(
              $._newline,
              $.children,
            )
          ),
        ),
      ),
    block_definition: ($) =>
      seq(
        alias('block', $.keyword),
        $._block_content,
      ),
    block_append: ($) =>
      seq(
        alias(optional('block'), $.keyword),
        alias('append', $.keyword),
        $._block_content,
      ),
    block_prepend: ($) =>
      seq(
        alias(optional('block'), $.keyword),
        alias('prepend', $.keyword),
        $._block_content,
      ),
    extends: ($) =>
      seq(
        alias('extends', $.keyword),
        alias(/[^\n]+/, $.filename),
      ),

    filter: ($) =>
      prec.right(
        seq(
          ':',
          $.filter_name,
          optional($.attributes),
          optional(
            alias($.filter_content, $.content),
          ),
      ),
    ),
    filter_name: () => /[\w-]+/,
    filter_content: ($) =>
      choice(
        $.filter,
        seq(
          /( |\t)+/,
          /[^\n]*/,
        ),
        seq(
          $._newline,
          $._indent,
          repeat(
            seq(
              /[^\n]*/,
              $._newline,
            ),
          ),
          $._dedent,
        )
      ),

    conditional: ($) =>
      seq(
        choice(
          seq(
            alias(
              choice(
                'unless',
                'if',
                'else if',
              ),
              $.keyword,
            ),
            alias($._un_delimited_javascript, $.javascript),
          ),
          alias('else', $.keyword),
        ),
        $._newline,
        $.children,
      ),
    case: ($) =>
      prec.right(
        seq(
          alias('case', $.keyword),
          alias($._un_delimited_javascript_line, $.javascript),
          $._newline,
          $._indent,
          repeat1(
            $.when,
          ),
        ),
      ),
    _when_content: ($) =>
      seq(
        choice(
          // Where the content is on the next line
          seq(
            $._newline,
            $.children,
          ),
          // Where the content follows a : on the same line
          seq(
            ':',
            alias($._dummy_tag, $.children),
          ),
        ),
      ),
    _dummy_tag: ($) => $.tag,
    _when_keyword: ($) =>
      choice(
        seq(
          alias('when', $.keyword),
          // `when`s don't work with properly with objects, so removing : from regex is fine.
          alias(/[^:\n]+?/, $.javascript),
        ),
        alias('default', $.keyword),
      ),
    when: ($) =>
      prec.left(
        seq(
          $._when_keyword,
          choice(
            $._when_content,
            // There are newlines between each when case, but not the last when
            $._newline,
          ),
          optional($._dedent)
        ),
      ),
    unescaped_buffered_code: ($) =>
      seq(
        '!=',
        $._single_line_buf_code,
      ),
    buffered_code: ($) =>
      seq(
        '=',
        $._single_line_buf_code,
      ),
    script_block: ($) =>
      seq(
        'script.',
        $._newline,
        $._indent,
        alias(
          repeat1(
            seq(
              optional(/[^\n]+/),
              $._newline,
            )
          ),
          $.javascript
        ),
        $._dedent,
      ),
    tag: ($) =>
      seq(
        choice($.tag_name, $.id, $.class),
        optional(repeat1(choice($.id, $.class))),
        optional($.attributes),
        optional(alias('/', $.self_close_slash)),
        choice(
          seq(":", $.tag),
          $._content_after_dot,
          seq(
            optional(
              seq(
                $._newline,
                $._indent,
              ),
            ),
            choice($.buffered_code, $.unescaped_buffered_code),
          ),
          seq(
            optional(seq(" ", $._content_or_javascript)),
            $._newline,
            optional($.children)
          )
        )
      ),
    _content_after_dot: ($) =>
      seq(
        optional(
          seq(
            $._newline,
            $._indent,
          )
        ),
        ".",
        $._newline,
        $._indent,
        alias(
          repeat1(seq(optional($._content_or_javascript), $._newline)),
          $.children
        ),
        $._dedent,
      ),

    attributes: ($) =>
      seq(
        "(",
        repeat(seq($.attribute, choice(",", " "))),
        optional($.attribute),
        ")"
      ),
    attribute: ($) =>
      choice(
        $._attribute,
        $._angular_attribute,
      ),
    _ternary_attribute_value: ($) =>
      seq(
        alias(
          token(
            seq(
              /[^'"`{\[][^?]+?/,
              '?',
              /[^)?]+?/,
              choice(
                /[^ )]*?/,
                choice(
                  /'(?:[^'\\]|\\.)*'/,
                  /"(?:[^"\\]|\\.)*"/,
                  /`(?:[^`\\]|\\.)*`/,
                ),
              ),
            )
          ),
          $.javascript
        ),
      ),
    _string_attribute_value: ($) =>
      $.quoted_attribute_value,
    _variable_attribute_value: ($) =>
      seq(
        alias(
          // No function calls, nor spaces allowed in javascript attributes
          /[^'"`{\[][^ ,()]+(\([^)]*?\))?/,
          $.javascript
        ),
      ),
    _object_attribute_value: ($) =>
      seq(
        alias(
          token(
            seq(
              "{",
              /([^\[\]()]*?(, ?)?)*?/,
              "}",
            ),
          ),
          $.javascript,
        ),
      ),
    _template_attribute_value: ($) =>
      seq(
        alias(
          token(
            seq(
              "`",
              /(?:[^`\\]|\\.)*/,
              "`",
            ),
          ),
          $.javascript,
        ),
      ),
    _array_attribute_value: ($) =>
      seq(
        alias(
          token(
            seq(
              "[",
              /[^\[\]()]*?/,
              "]",
            ),
          ),
          $.javascript,
        ),
      ),
      _pug_attributes: ($) =>
        choice(
          $._string_attribute_value,
          $._ternary_attribute_value,
          $._variable_attribute_value,
          $._array_attribute_value,
          $._object_attribute_value,
          $._template_attribute_value,
        ),
    _attribute: ($) =>
      seq(
        $.attribute_name,
        optional(repeat1(seq(".", alias(/[\w@\-:]+/, $.attribute_modifier)))),
        optional(
          seq(
            '=',
            $._pug_attributes
          )
        ),
      ),
    _angular_attribute: ($) =>
      seq(
        alias($.angular_attribute_name, $.attribute_name),
        optional(seq("=", $.quoted_javascript))
      ),

    children: ($) => prec.right(
      seq(
        $._indent,
        repeat1($._children_choice),
        optional($._dedent),
      ),
    ),
    // TODO: add all other types of element in here too
    _children_choice: ($) =>
      prec(1,
        choice(
          $.buffered_code,
          $.case,
          $.comment,
          $.conditional,
          $.doctype,
          $.pipe,
          $.script_block,
          $.tag,
          $.unbuffered_code,
          $.unescaped_buffered_code,
          $.filter,
          $.block_definition,
          $.block_append,
          $.block_prepend,
          $.extends,
          $.each,
          $.while,
          $.include,
          $._newline,
        ),
      ),

    comment: ($) =>
      choice(
        $._comment,
        $._comment_not_first_line,
      ),
    _comment: ($) =>
      prec.left(
        seq(
          choice("//", "//-"),
          $._comment_content,
          $._newline,
          optional(
            seq(
              $._indent,
              repeat1(
                seq(
                  $._comment_content,
                  $._newline,
                ),
              ),
              $._dedent,
            ),
          ),
        ),
      ),
    _comment_not_first_line: ($) =>
      seq(
        choice("//", "//-"),
        $._newline,
        $._indent,
        repeat1(
          seq(
            $._comment_content,
            $._newline,
          ),
        ),
        $._dedent,
      ),

    tag_name: () => /\w(?:[-\w]*\w)?/,
    class: () => /\.[_a-z0-9\-]*[_a-zA-Z][_a-zA-Z0-9\-]*/i,
    id: () => /#[\w-]+/,

    angular_attribute_name: () =>
      choice(
        /\[[\w@\-:\.]+\]/, // [input]
        /\([\w@\-:\.]+\)/, // (output)
        /\[\([\w@\-:\.]+\)\]/, // [(both)]
        /\*[\w@\-:\.]+/, // *directive
      ),
    attribute_name: () => /#?[\w@\-:]+/,

    quoted_javascript: ($) =>
      choice(
        seq("'", optional(alias(/(?:[^'\\]|\\.)+/, $.javascript)), "'"),
        seq('"', optional(alias(/(?:[^"\\]|\\.)+/, $.javascript)), '"'),
      ),
    quoted_attribute_value: ($) =>
      choice(
        seq("'", optional(alias(/(?:[^'\\]|\\.)+/, $.attribute_value)), "'"),
        seq('"', optional(alias(/(?:[^"\\]|\\.)+/, $.attribute_value)), '"'),
      ),

    content: () =>
      prec.right(
        repeat1(
          seq(
            /[^\n{#]+?/,
            optional('#'),
            optional('{')
          ),
        ),
      ),
    _comment_content: () => /[^\n]*/,
    _content_or_javascript: ($) =>
      repeat1(
        choice(
          seq(
            "#{",
            alias($._delimited_javascript, $.javascript),
            "}"
          ),
          seq(
            "{{",
            alias($._delimited_javascript, $.javascript),
            "}}"
          ),
          $.content
        ),
      ),

    // TODO: can _delimited_javascript and _un_delimited_javascript be merged?
    _delimited_javascript: () => /[^\n}]+/,
    // I only want this node to be exposed sometimes
    _un_delimited_javascript: ($) => $._un_delimited_javascript_line,
    _un_delimited_javascript_line: ($) => /(.)+?/,
    _un_delimited_javascript_multiline: ($) => repeat1(prec(1, $._un_delimited_javascript_line)),
    _single_line_buf_code: ($) =>
      prec.left(
        seq(
          alias($._un_delimited_javascript, $.javascript),
          choice(
            seq(
              $._newline,
              $._indent,
              repeat1(
                choice(
                  $.tag,
                  $._newline,
                ),
              ),
              $._dedent,
            ),
            $._newline,
          ),
          optional($._dedent),
        ),
      ),
    _multi_line_buf_code: ($) =>
      alias(seq(
        $._un_delimited_javascript_multiline,
      ), $.javascript),
    unbuffered_code: ($) =>
      prec.right(
        seq(
          '-',
          token.immediate(/( |\t)*/),
          choice(
            seq(
              $._single_line_buf_code,
            ),
            seq(
              $._newline,
              $._indent,
              $._multi_line_buf_code,
            ),
          ),
          optional($._dedent),
        )
      )
  },
});