source: node_modules/prismjs/components/prism-dot.js

// https://www.graphviz.org/doc/info/lang.html

(function (Prism) {

        var ID = '(?:' + [
                // an identifier
                /[a-zA-Z_\x80-\uFFFF][\w\x80-\uFFFF]*/.source,
                // a number
                /-?(?:\.\d+|\d+(?:\.\d*)?)/.source,
                // a double-quoted string
                /"[^"\\]*(?:\\[\s\S][^"\\]*)*"/.source,
                // HTML-like string
                /<(?:[^<>]|(?!<!--)<(?:[^<>"']|"[^"]*"|'[^']*')+>|<!--(?:[^-]|-(?!->))*-->)*>/.source
        ].join('|') + ')';

        var IDInside = {
                'markup': {
                        pattern: /(^<)[\s\S]+(?=>$)/,
                        lookbehind: true,
                        alias: ['language-markup', 'language-html', 'language-xml'],
                        inside: Prism.languages.markup
                }
        };

        /**
         * @param {string} source
         * @param {string} flags
         * @returns {RegExp}
         */
        function withID(source, flags) {
                return RegExp(source.replace(/<ID>/g, function () { return ID; }), flags);
        }

        Prism.languages.dot = {
                'comment': {
                        pattern: /\/\/.*|\/\*[\s\S]*?\*\/|^#.*/m,
                        greedy: true
                },
                'graph-name': {
                        pattern: withID(/(\b(?:digraph|graph|subgraph)[ \t\r\n]+)<ID>/.source, 'i'),
                        lookbehind: true,
                        greedy: true,
                        alias: 'class-name',
                        inside: IDInside
                },
                'attr-value': {
                        pattern: withID(/(=[ \t\r\n]*)<ID>/.source),
                        lookbehind: true,
                        greedy: true,
                        inside: IDInside
                },
                'attr-name': {
                        pattern: withID(/([\[;, \t\r\n])<ID>(?=[ \t\r\n]*=)/.source),
                        lookbehind: true,
                        greedy: true,
                        inside: IDInside
                },
                'keyword': /\b(?:digraph|edge|graph|node|strict|subgraph)\b/i,
                'compass-point': {
                        pattern: /(:[ \t\r\n]*)(?:[ewc_]|[ns][ew]?)(?![\w\x80-\uFFFF])/,
                        lookbehind: true,
                        alias: 'builtin'
                },
                'node': {
                        pattern: withID(/(^|[^-.\w\x80-\uFFFF\\])<ID>/.source),
                        lookbehind: true,
                        greedy: true,
                        inside: IDInside
                },
                'operator': /[=:]|-[->]/,
                'punctuation': /[\[\]{};,]/
        };

        Prism.languages.gv = Prism.languages.dot;

}(Prism));