nunjucks-highlight.js/lib/index.js

A custom nunjucks tag to highlight code blocks using highlight.js

module.exports = function NunjucksCodeHighlight (nunjucks, hljs) {
    this.tags = ["code"];

    this.parse = function (parser, nodes) {
        // get the tag token
        var tok = parser.nextToken();

        // parse the args and move after the block end. passing true
        // as the second arg is required if there are no parentheses
        var args = parser.parseSignature(null, true);
        parser.advanceAfterBlockEnd(tok.value);

        // If arguments, return the fileTag constructed node
        if (args.children.length > 0)
            return new nodes.CallExtension(this, "fileTag", args);

        // parse the body and possibly the error block, which is optional
        var body = parser.parseUntilBlocks("endcode");

        // I found Nunjucks  to be incredibly convoluted on how to just get some data into the BlockTag function,
        // this finally worked by faking another template node.
        var tabStart = new nodes.NodeList(0, 0, [
            new nodes.Output(0, 0, [
                new nodes.TemplateData(0, 0, (tok.colno - 1))
            ])
        ]);

        parser.advanceAfterBlockEnd();

        // See above for notes about CallExtension
        return new nodes.CallExtension(this, "blockTag", args, [body, tabStart]);
    };

    // code rendering for the file tag. Use the nunjucks.render function to render
    // the actual contents of the file. Pass the results through the code renderer.
    // this.fileTag = function(environment, file) {
    //      return new nunjucks.runtime.SafeString(...)
    //    }

    // code rendering for the block. Pretty simple, just get the body text and pass
    // it through the code renderer.
    this.blockTag = function (environment, blockTagBody, blockTagTabStart) {

        var body = blockTagBody();
        var spacesRegex = /^[\s]+/;
        var tabStart = blockTagTabStart(); // The column postion of the {% code %} tag.

        if (tabStart > 0) { // If the {% code %} tag is tabbed in, normalize the content to the same depth.
            body = body.split(/\r?\n/); // Split into lines.
            body = body.map(function (line) {
                var startSpaces = line.match(spacesRegex);
                // If the content is not at the same or greater tab depth, do nothing..
                if (startSpaces && startSpaces[0].length >= tabStart) {
                    return line.slice(tabStart); // Subtract the column position from the start of the string.
                } else {
                    return line;
                }
            });

            // remove blank start and end lines to be safe
            if (body[0] === "")
                body = body.slice(1);
            if (body[body.length - 1] === "")
                body = body.slice(0, body.length - 1);

            body = body.join("\n"); // Rejoin into one string.

        }

        // remove line break from start and end of string
        // <http://stackoverflow.com/a/14572494>
        body = body.replace(/^\s+|\s+$/, "");

        // get the first line of the body to see if we have a file type specified
        var value = hljs.highlightAuto(body).value;
        if (body.split("\n").length > 1) {
            var lang = hljs.getLanguage(body.split("\n")[0]);
            if (lang) {
                lang = body.split("\n")[0];
                body = body.split("\n").slice(1).join("\n");
                value = hljs.highlight(lang, body).value;
            }
        }

        return new nunjucks.runtime.SafeString("<pre><code class=\"hljs\">" + value + " </code></pre>");
    };
};