Gingerly Tree

Syntax highlighting for assign-gingerly's tree`…` tagged templates, which produce builtIns.tree element specifications from lit-like markup.

import { tree, each } from 'assign-gingerly/DX/tree.js';

const map = {
    launch: tree`
        <article class="card" aria-label=${p.label}>
            <h3 class="title">${p.name}</h3>
            <p>Launched ${p.date} by ${'?.rocket'}</p>
            <ul ${each(p.crew, { key: '?.id' })}>
                <li>${'?.name'}</li>
            </ul>
            <button @click=${{ call: 'launch' }}>Launch</button>
        </article>`,
};

This extension has no extension-host code: TextMate grammars, plus a script and stylesheet that run inside the Markdown Preview. So it also works in VS Code for the Web (vscode.dev, github.dev) and in untrusted workspaces.

Where it works

Recognized tags

• tree`…`
• 🌲`…`
• DX.tree`…`

A grammar matches by name, so other aliases (import { tree as t }) aren't highlighted.

What's highlighted

• Markup: tags, attributes, quoted and unquoted values, entities, comments.
• Binding prefixes, each with its own scope:
  • .prop=${…}: a property;
  • @event=${…}: an event binding;
  • ish=${Manager}: the itemscope manager header.
• ${…}: colored as TypeScript/JavaScript. That covers ${p.name}, ${each(…)}, pattern spreads ${{ … }}, and nested ${tree`…`}.
• ?. path strings inside ${…}, e.g. ${'?.name'}, '$parent?.upcoming' or '?.date_utc?.parseDate?.longUtc'. They're scoped as variables rather than strings, so most themes show them in a different color from ordinary strings.

In the Markdown Preview

The preview doesn't use TextMate grammars: it colors code blocks with highlight.js, which shows a tagged template as one plain string. So this extension adds a small script to the preview (preview/gingerly-tree-preview.js). It finds the tree templates in JS/TS code blocks and in <script> tags of HTML code blocks, and re-renders them with the same rules as the grammar. Markup uses the preview's own highlight.js colors. .prop, @event, ish, ${…} and ?. paths get Dark+ / Light+ colors from preview/gingerly-tree-preview.css.

The preview isn't affected by editor.tokenColorCustomizations. To restyle it, point markdown.styles at your own CSS, targeting .gt-path-segment, .gt-path-root, .gt-path-accessor, .gt-prefix, .gt-event, .gt-prop, .gt-ish, .gt-subst, .gt-entity or .gt-escape.

GitHub's own rendering of Markdown uses its own highlighter, which no extension can change.

Customizing colors

All scopes end in .gingerly-tree, so they can be targeted in settings.json:

"editor.tokenColorCustomizations": {
    "textMateRules": [
        { "scope": "meta.path.gingerly-tree", "settings": { "foreground": "#4EC9B0" } },
        { "scope": "punctuation.accessor.optional.path.gingerly-tree", "settings": { "foreground": "#808080" } },
        { "scope": "entity.other.attribute-name.event.gingerly-tree", "settings": { "fontStyle": "italic" } },
        { "scope": "entity.other.attribute-name.property.gingerly-tree", "settings": { "fontStyle": "italic" } },
        { "scope": "entity.other.attribute-name.ish.gingerly-tree", "settings": { "fontStyle": "bold" } }
    ]
}

Not included

Diagnostics (the tag's TreeTemplateErrors), hover previews of the produced tree notation and completions need code, so they're planned for a separate extension, Gingerly Tree Analyzer, which will depend on this one for highlighting.

Development

npm install
npm test          # runs both test suites below
node test/run.mjs                    # tokenizes test/fixtures with VS Code's built-in grammars plus these, and checks scopes
node test/preview.mjs                # renders test/fixtures/preview.md as the preview does (markdown-it + highlight.js), runs the preview script in jsdom, checks the spans
node test/run.mjs --dump sample.md   # prints every token of a fixture

The tests load the built-in grammars from the local VS Code install. If it isn't found, set VSCODE_EXTENSIONS_DIR to <VS Code>/resources/app/extensions.

To try the extension, open this folder in VS Code and press F5 (Run Extension), or install a packaged .vsix (see StepsToPublish.md).