Commenting gate.ts

While reading the codebase, I was briefly confused by the gate decorator.

For a second, I thought `gate to what?`
![](https://media2.giphy.com/media/KcJO5G7N7nsxe9nRku/giphy.gif?cid=ecf05e476typvmnukv78gz55o21rcvlm025dw6w3m0djk5sw)

I'm hoping these comments will help others dive through the codebase as well 🙂

Author: sadasant

src/system/decorators/gate.ts

@@ -2,8 +2,14 @@
 import { isPromise } from '../promise';
 import { resolveProp } from './resolver';
 
+/**
+ * A decorator that gates the execution of a method or getter.
+ * It ensures that the decorated method is executed only once at a time
+ * by forcing subsequent calls to wait for the previous execution to complete.
+ */
 export function gate<T extends (...arg: any) => any>(resolver?: (...args: Parameters<T>) => string) {
 	return (target: any, key: string, descriptor: PropertyDescriptor) => {
+		// Stores the original method or getter function in fn variable
 		let fn: Function | undefined;
 		if (typeof descriptor.value === 'function') {
 			fn = descriptor.value;
@@ -12,10 +18,15 @@ export function gate<T extends (...arg: any) => any>(resolver?: (...args: Parame
 		}
 		if (fn == null) throw new Error('Not supported');
 
+		// Creates a unique gate key
 		const gateKey = `$gate$${key}`;
 
+		// Replaces the descriptor value with a new function
 		descriptor.value = function (this: any, ...args: any[]) {
+			// Resolves the gate key using the resolver function
 			const prop = resolveProp(gateKey, resolver, ...(args as Parameters<T>));
+
+			// Checks if a promise has already been created for the method
 			if (!Object.prototype.hasOwnProperty.call(this, prop)) {
 				Object.defineProperty(this, prop, {
 					configurable: false,
@@ -25,15 +36,21 @@ export function gate<T extends (...arg: any) => any>(resolver?: (...args: Parame
 				});
 			}
 
+			// If a promise exists, return it
 			let promise = this[prop];
 			if (promise === undefined) {
 				let result;
 				try {
+					// Call the original method
 					result = fn!.apply(this, args);
+
+					// If the result is not a promise, return it
 					if (result == null || !isPromise(result)) {
 						return result;
 					}
 
+					// If the result is a promise, set up .then and .catch
+					// handlers to clear the promise on completion
 					this[prop] = promise = result
 						.then((r: any) => {
 							this[prop] = undefined;
@@ -49,6 +66,7 @@ export function gate<T extends (...arg: any) => any>(resolver?: (...args: Parame
 				}
 			}
 
+			// Return the ongoing promise
 			return promise;
 		};
 	};