fix(core): amend typing for jsonParse() options (#4423)

* 📘 Amend typing for `jsonParse()` options

* ✏️ Update rule message and description

* 🔀 Cherrypick Adi's work

* 🐛 Account for falsy fallback values

* ♻️ Use `else if`

* ⚡ Add explicit error message as type

* ⚡ Consolidate utils tests

* ♻️ Use optional chaining

* 🔥 Remove patchy type error

Co-authored-by: कारतोफ्फेलस्क्रिप्ट™ <aditya@netroy.in>

packages/workflow/src/utils.test.ts

@@ -1,34 +0,0 @@
-import { deepCopy } from './utils';
-
-describe('deepCopy', () => {
-	it('should deep copy an object', () => {
-		const object = {
-			deep: {
-				props: {
-					list: [{ a: 1 }, { b: 2 }, { c: 3 }],
-				},
-				arr: [1, 2, 3],
-			},
-			arr: [
-				{
-					prop: {
-						list: ['a', 'b', 'c'],
-					},
-				},
-			],
-			func: () => {},
-			date: new Date(),
-			undef: undefined,
-			nil: null,
-			bool: true,
-			num: 1,
-		};
-		const copy = deepCopy(object);
-		expect(copy).toEqual(object);
-		expect(copy).not.toBe(object);
-		expect(copy.arr).toEqual(object.arr);
-		expect(copy.arr).not.toBe(object.arr);
-		expect(copy.deep.props).toEqual(object.deep.props);
-		expect(copy.deep.props).not.toBe(object.deep.props);
-	});
-});

packages/workflow/src/utils.ts

@@ -30,22 +30,23 @@ export const deepCopy = <T>(source: T): T => {
 	return clone;
 };
 // eslint-enable
-type ErrorMessage = { errorMessage: string };
-type FallbackValue<T> = { fallbackValue: T };
 
-export const jsonParse = <T>(
-	jsonString: string,
-	options: ErrorMessage | FallbackValue<T> | {} = {},
-): T => {
+type MutuallyExclusive<T, U> =
+	| (T & { [k in Exclude<keyof U, keyof T>]?: never })
+	| (U & { [k in Exclude<keyof T, keyof U>]?: never });
+
+type JSONParseOptions<T> = MutuallyExclusive<{ errorMessage: string }, { fallbackValue: T }>;
+
+export const jsonParse = <T>(jsonString: string, options?: JSONParseOptions<T>): T => {
 	try {
 		return JSON.parse(jsonString) as T;
 	} catch (error) {
-		if ('fallbackValue' in options) {
+		if (options?.fallbackValue !== undefined) {
 			return options.fallbackValue;
-		}
-		if ('errorMessage' in options) {
+		} else if (options?.errorMessage) {
 			throw new Error(options.errorMessage);
 		}
+
 		throw error;
 	}
 };