@surface/custom-element/internal/metadata/metadata.js

Provides support of directives and data binding on custom elements.

export const METADATA = Symbol("custom-element:metadata");
export default class Metadata {
    constructor() {
        this.isPropagatingCallback = false;
        this.reflectingAttribute = new Set();
    }
    static from(target) {
        if (!Reflect.has(target, METADATA)) {
            Reflect.defineProperty(target, METADATA, { configurable: false, enumerable: false, value: new Metadata() });
        }
        return Reflect.get(target, METADATA);
    }
}