@github/template-parts/lib/template-instance.js

An implementation of the TemplateInstance proposal (https://github.com/w3c/webcomponents/blob/159b1600bab02fe9cd794825440a98537d53b389/proposals/Template-Instantiation.md)

import { parse } from './template-string-parser.js';
import { AttributeValueSetter, AttributeTemplatePart } from './attribute-template-part.js';
import { InnerTemplatePart } from './inner-template-part.js';
import { NodeTemplatePart } from './node-template-part.js';
import { propertyIdentity } from './processors.js';
function* collectParts(el) {
    const walker = el.ownerDocument.createTreeWalker(el, NodeFilter.SHOW_TEXT | NodeFilter.SHOW_ELEMENT, null);
    let node;
    while ((node = walker.nextNode())) {
        if (node instanceof HTMLTemplateElement) {
            if (node.hasAttribute('directive')) {
                yield new InnerTemplatePart(node);
            }
            else {
                for (const part of collectParts(node.content)) {
                    yield part;
                }
            }
        }
        else if (node instanceof Element && node.hasAttributes()) {
            for (let i = 0; i < node.attributes.length; i += 1) {
                const attr = node.attributes.item(i);
                if (attr && attr.value.includes('{{')) {
                    const valueSetter = new AttributeValueSetter(node, attr);
                    for (const token of parse(attr.value)) {
                        if (token.type === 'string') {
                            valueSetter.append(token.value);
                        }
                        else {
                            const part = new AttributeTemplatePart(valueSetter, token.value);
                            valueSetter.append(part);
                            yield part;
                        }
                    }
                }
            }
        }
        else if (node instanceof Text && node.textContent && node.textContent.includes('{{')) {
            const parsed = parse(node.textContent);
            // A for..of loop would be nicer here, unfortunately Safari had a runtime error on this loop.
            // https://github.com/github/template-parts/pull/55
            for (let i = 0; i < parsed.length; i += 1) {
                const token = parsed[i];
                if (token.end < node.textContent.length)
                    node.splitText(token.end);
                if (token.type === 'part')
                    yield new NodeTemplatePart(node, token.value);
                break;
            }
        }
    }
}
const processors = new WeakMap();
const parts = new WeakMap();
export class TemplateInstance extends (globalThis.DocumentFragment || EventTarget) {
    constructor(template, params, processor = propertyIdentity) {
        var _a, _b;
        super();
        // This is to fix an inconsistency in Safari which prevents us from
        // correctly sub-classing DocumentFragment.
        // https://bugs.webkit.org/show_bug.cgi?id=195556
        if (Object.getPrototypeOf(this) !== TemplateInstance.prototype) {
            Object.setPrototypeOf(this, TemplateInstance.prototype);
        }
        this.appendChild(template.content.cloneNode(true));
        parts.set(this, Array.from(collectParts(this)));
        processors.set(this, processor);
        (_b = (_a = processors.get(this)).createCallback) === null || _b === void 0 ? void 0 : _b.call(_a, this, parts.get(this), params);
        processors.get(this).processCallback(this, parts.get(this), params);
    }
    update(params) {
        processors.get(this).processCallback(this, parts.get(this), params);
    }
}
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