How can I sort nested lists in AST?

[ylor]

Hello,

I would like to sort the following Markdown lists, maintain nesting, and not affect the rest of the content.

What I have:

# Animals
- Zoo Animals
  - Herbivores
    - Zebra
    - Gazelle
  - Carnivores
    - Tiger
    - Lion
  - Omnivores
    - Gorilla
    - Baboon
    - Chimpanzee
- Domestic Animals
  - Felines
    - Tabby
    - Bengal
    - Siamese
  - Canines
    - German Shepherd
    - Cocker Spaniel

Result I am aiming for:

# Animals
- Domestic Animals
  - Canines
    - Cocker Spaniel
    - German Shepherd
  - Felines
    - Bengal
    - Siamese
    - Tabby
- Zoo Animals
  - Carnivores
    - Lion
    - Tiger
  - Herbivores
    - Gazelle
    - Zebra
  - Omnivores
    - Baboon
    - Chimpanzee
    - Gorilla

The following is as far as I have been able to get:

const text =
  "# Animals\n" +
  "- Zoo Animals\n" +
  "  - Herbivores\n" +
  "    - Zebra\n" +
  "    - Gazelle\n" +
  "  - Carnivores\n" +
  "    - Tiger\n" +
  "    - Lion\n" +
  "  - Omnivores\n" +
  "    - Gorilla\n" +
  "    - Baboon\n" +
  "    - Chimpanzee\n" +
  "- Domestic Animals\n" +
  "  - Felines\n" +
  "    - Tabby\n" +
  "    - Bengal\n" +
  "    - Siamese\n" +
  "  - Canines\n" +
  "    - German Shepherd\n" +
  "    - Cocker Spaniel\n";

const unified = require("unified");
const markdown = require("remark-parse");
const tree = unified().use(markdown).parse(text);
console.log("raw", tree);

const visit = require("unist-util-visit");
visit(tree, "list", (node) => {
  console.log("walked", node);
  visit(node, "text", (textNode) => console.log(textNode.value));
});

I hope that's enough info to go off of. Been banging my head against this for a couple of hours now so any help is appreciated. Thank you!

[ylor]

Solved this and it was simpler than I thought. 😅

const text =
  "# Animals\n" +
  "- Zoo Animals\n" +
  "  - Herbivores\n" +
  "    - Zebra\n" +
  "    - Gazelle\n" +
  "  - Carnivores\n" +
  "    - Tiger\n" +
  "    - Lion\n" +
  "  - Omnivores\n" +
  "    - Gorilla\n" +
  "    - Baboon\n" +
  "    - Chimpanzee\n" +
  "- Domestic Animals\n" +
  "  - Felines\n" +
  "    - Tabby\n" +
  "    - Bengal\n" +
  "    - Siamese\n" +
  "  - Canines\n" +
  "    - German Shepherd\n" +
  "    - Cocker Spaniel\n";

const unified = require("unified");
const remarkParse = require("remark-parse");
const remarkStringify = require("remark-stringify");
const visit = require("unist-util-visit");

// parse markdown into mdast tree
const tree = unified().use(remarkParse).parse(text);

// visit each list node and sort children based on children[0].children[0].value
visit(tree, "list", (node) => {
  node.children.sort(function (a, b) {
    // Normalize casing for sorting
    let listItemA = a.children[0].children[0].value.toLowerCase();
    let listItemB = b.children[0].children[0].value.toLowerCase();

    let comparison = 0;
    if (listItemA > listItemB) {
      comparison = 1;
    } else if (listItemA < listItemB) {
      comparison = -1;
    }
    return comparison;
  });
});

// serialize from mdast back to markdown
const doc = unified().use(remarkStringify).stringify(tree);
console.log(doc);

[wooorm]

Nice! Sorry for missing this!

You might be interested in using locale data to sort btw: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/localeCompare

[ylor]

Thanks for that! Looking into localeCompare led me to Intl.Collator. Ended up rolling it into a simple plugin for mdast called mdast-sort-lines.

Github
npm

Hope it helps someone!