@exadel/esl/modules/esl-utils/decorators/decorate.js

Exadel Smart Library (ESL) is the lightweight custom elements library that provide a set of super-flexible components

import { getPropertyDescriptor } from '../misc/object/utils';
/**
 * `@decorate` decorator: adapts a higher-order function `(fn) => wrappedFn` into a lazy method decorator.
 * - Applies only to class (prototype or static) methods (value descriptors)
 * - First instance access: binds original to `this`, passes it to `decorator(...args)`, caches wrapped fn on the instance
 * - Prototype (or super) access returns the original unwrapped function
 * - Reassignment replaces accessor with a normal writable value (no further wrapping)
 * - Copy of original own enumerable properties is assigned to the wrapped function
 *
 * @param decorator - higher‑order function receiving the bound original method
 * @param args - extra arguments forwarded to `decorator` after the original function
 * @throws TypeError when applied to a non-method (accessor / field)
 */
export function decorate(decorator, ...args) {
    return function (target, propertyKey, descriptor) {
        if (!descriptor || typeof descriptor.value !== 'function') {
            throw new TypeError('Only class methods can be decorated');
        }
        const originalFn = descriptor.value;
        return descriptor = {
            enumerable: descriptor.enumerable,
            configurable: true,
            get: function getBound() {
                // Skip own properties
                const proto = Object.getPrototypeOf(this);
                // Find the closest descriptor for property
                const desc = getPropertyDescriptor(proto, propertyKey);
                // Return original function in case of prototype or super call
                if (!desc || desc.get !== getBound)
                    return originalFn;
                // Create a new decorated instance of function (original first bound to instance)
                const decoratedFn = decorator(originalFn.bind(this), ...args);
                // Copy original function own keys
                Object.assign(decoratedFn, originalFn);
                // Defines own property with the decorated instance
                return this[propertyKey] = decoratedFn;
            },
            set(value) {
                Object.defineProperty(this, propertyKey, {
                    value,
                    writable: true,
                    configurable: true,
                    enumerable: descriptor.enumerable
                });
            }
        };
    };
}