Fix optional attributes in a parent factory causing all attributes to be required in a child factory (#39)

Author: davidtkramer

package.json

@@ -1,6 +1,6 @@
 {
   "name": "typical-data",
-  "version": "0.4.1",
+  "version": "0.4.2",
   "description": "Test data factory",
   "homepage": "https://github.com/davidtkramer/typical-data",
   "main": "./dist/index.js",

src/__tests__/factory.test.ts

@@ -265,6 +265,7 @@ describe('DSL', () => {
       interface BaseContact {
         id: number;
         phone: string;
+        meta?: string;
       }
       const baseFactory = createFactory((factory) =>
         factory
@@ -275,6 +276,7 @@ describe('DSL', () => {
             id: 1,
             phone: ({ transientParams }) =>
               `(${transientParams.areaCode}) 123-4567`,
+            meta: undefined,
           })
           .trait('invalidPhone', { phone: 'asdf' })
           .trait('withCountryCode', (trait) =>

src/types.ts

@@ -9,10 +9,11 @@ export type TransientParamsForTraits<
 /**
  * Converts a union of values to an intersection of values.
  */
-export type Intersect<U> = {
-  [K in GetKeys<U>]: U extends Record<K, infer T> ? T : never;
-};
-type GetKeys<U> = U extends Record<infer K, any> ? K : never;
+export type Intersect<T> = (T extends any ? (x: T) => any : never) extends (
+  x: infer R
+) => any
+  ? R
+  : never;
 
 /**
  * Makes optional the keys on Child that also exist on Parent.