A port of the commonmark.js Markdown parser and renderer to Ceylon
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This is a port of the commonmark.js Markdown parser and renderer from JavaScript to Ceylon. Some parts have been made more ceylonic, for convenience, but the overall structure of the code still resembles the original JavaScript, to make incorporating upstream changes easier.

This repository includes the main ceylon.markdown module, its accompanying suite of tests, and two utility modules that generate parts of the code.


Similarly to commonmark.js, parsing and rendering are performed in separate steps:

value root = Parser().parse("## Hello World!");

The parse operation returns the root of a tree of parsed nodes that can be passed to one of the renderers:

// Render as a String of HTML:
value html = RawHtmlRenderer().render(root);

// Render as a sequence of ceylon.html elements:
value elements = CeylonHtmlRenderer().render(root);


The parser and renderers support options similar to those found in commonmark.js:

value parser = Parser(ParseOptions { smart = true; });
value renderer = RawHtmlRenderer(RenderOptions { defaultLanguage = "ceylon"; });

The parser supports the following options:

  • smart: Enables "smart" processing of quotation marks, dashes, and ellipses.
  • specialLinks: Enables parsing of "special" links (see the next section).
  • time: Enables logging of timing statistics, for debugging.

The renderers support the following options:

  • defaultLanguage: Indicates a language to be used when rendering code blocks that don't already specify one.
  • linkHeadings: Renders headings as links that scroll the page to themselves.
  • safe: Removes certain HTML from the output and limits the types of URL's in links and images.
  • softBreak: Specifies a snippet of HTML that should be used for "soft" breaks, which include single line breaks that don't interrupt the current paragraph.
  • sourcePos: Renders data-sourcepos attributes in the HTML that indicate where in the source text the Markdown that generated the current element was located.

"Special" links

When the specialLinks option is enabled, the parser will look for text surrounded by double brackets and parse them as nodes with a unique type. Code can subsequently search the tree for such nodes and apply a transformation on them. The transformSpecialLinks function has been provided to make this job easier.

Here's an example of how one could transform special links:

import ceylon.markdown.parser {
import ceylon.markdown.renderer {

Node createLinkNode(String destination, String content) {
    value node = Node(NodeType.link);
    node.destination = destination;
    value text = Node(NodeType.text);
    text.literal = content;
    return node;

shared void run() {
    value input
            = "## Testing special links
               Broken link: [[broken]], working link: [[link]].";
    value parseOptions = ParseOptions {
        specialLinks = true;
    value parser = Parser(parseOptions);
    value root = parser.parse(input);
    function transform(String content)
            => content != "broken" then createLinkNode("doc:``content``", content.uppercased);
    transformSpecialLinks(root, transform);
    value renderer = RawHtmlRenderer();

Utility modules


This module creates ceylon/markdown/parser/entityMap.ceylon, which contains the same entity map the original JavaScript code uses. This helps the Ceylon module produce identical output.


The JavaScript code targets the CommonMark spec for compliance testing, along with a few other test cases. The fetchspectests module parses the spec and extracts the test cases from it, allowing the Ceylon code to target the same tests.