feat: 🔥 Allow devs to pass in comparison functions

Add default comparison functions for most likely use cases. Implimented
them

✅ Closes: #220

packages/falso/src/lib/core/core.ts

@@ -13,17 +13,22 @@ type Return<T, O extends FakeOptions> = [O] extends [never]
 
 export function fake<T, Options extends FakeOptions>(
   data: T[] | (() => T),
-  options?: Options
+  options?: Options,
+  comparisonFunction: (
+    item: T,
+    items: T[]
+  ) => boolean = primitiveComparisonFunction
 ): Return<T, Options> {
   if (Array.isArray(data)) {
     return fakeFromArray(data, options) as any;
   }
 
-  return fakeFromFunction(data, options) as any;
+  return fakeFromFunction(data, comparisonFunction, options) as any;
 }
 
 export function fakeFromFunction<T, Options extends FakeOptions>(
   data: () => T,
+  comparisonFunction: (item: T, items: T[]) => boolean,
   options?: Options
 ) {
   if (!options?.length) {
@@ -44,7 +49,7 @@ export function fakeFromFunction<T, Options extends FakeOptions>(
   while (items.length < options.length && attempts < maxAttempts) {
     const item = data();
 
-    if (!items.includes(item)) {
+    if (!comparisonFunction(item, items)) {
       items.push(item);
     }
 
@@ -65,9 +70,7 @@ export function fakeFromArray<T, Options extends FakeOptions>(
   const priority = options?.priority ?? 'length';
 
   if (priority === 'length') {
-    return Array.from({ length: options.length }, (_, index) =>
-      randElement(data)
-    );
+    return Array.from({ length: options.length }, () => randElement(data));
   }
 
   const clonedData: T[] = JSON.parse(JSON.stringify(data));
@@ -84,6 +87,15 @@ export function fakeFromArray<T, Options extends FakeOptions>(
   return newArray;
 }
 
+export const primitiveComparisonFunction: <T>(item: T, items: T[]) => boolean =
+  (item, items) => items.includes(item);
+export const objectWithIdComparisonFunction: <T extends { id: string }>(
+  item: T,
+  items: T[]
+) => boolean = (item, items) => {
+  return items.some((i) => i.id === item.id);
+};
+
 export function randElement<T>(arr: T[]): T {
   return arr[Math.floor(random() * arr.length)];
 }

packages/falso/src/lib/post.ts

@@ -1,4 +1,4 @@
-import { FakeOptions, fake } from './core/core';
+import { FakeOptions, fake, objectWithIdComparisonFunction } from './core/core';
 import { randUser, User } from './user';
 import { randUuid } from './uuid';
 import { randText } from './text';
@@ -28,7 +28,7 @@ export interface Post {
 export function randPost<Options extends FakeOptions = never>(
   options?: Options
 ) {
-  return fake(() => {
+  const factory = () => {
     const post: Post = {
       id: randUuid(),
       title: randText({ charCount: 40 }),
@@ -43,5 +43,7 @@ export function randPost<Options extends FakeOptions = never>(
     };
 
     return post;
-  }, options);
+  };
+
+  return fake(factory, options, objectWithIdComparisonFunction);
 }

packages/falso/src/lib/product.ts

@@ -1,4 +1,9 @@
-import { FakeOptions, fake, getRandomInRange } from './core/core';
+import {
+  FakeOptions,
+  fake,
+  getRandomInRange,
+  objectWithIdComparisonFunction,
+} from './core/core';
 import { randUuid } from './uuid';
 import { randProductName } from './product-name';
 import { randProductDescription } from './product-description';
@@ -35,19 +40,18 @@ export interface Product {
 export function randProduct<Options extends FakeOptions = never>(
   options?: Options
 ) {
-  return fake(
-    () => ({
-      id: randUuid(),
-      title: randProductName(),
-      description: randProductDescription(),
-      price: getRandomInRange({ fraction: 2 }).toString(),
-      category: randProductCategory(),
-      image: randImg(),
-      rating: {
-        rate: getRandomInRange({ min: 0.1, max: 5.0, fraction: 1 }).toString(),
-        count: getRandomInRange({ min: 0, max: 10000 }).toString(),
-      },
-    }),
-    options
-  );
+  const factory = () => ({
+    id: randUuid(),
+    title: randProductName(),
+    description: randProductDescription(),
+    price: getRandomInRange({ fraction: 2 }).toString(),
+    category: randProductCategory(),
+    image: randImg(),
+    rating: {
+      rate: getRandomInRange({ min: 0.1, max: 5.0, fraction: 1 }).toString(),
+      count: getRandomInRange({ min: 0, max: 10000 }).toString(),
+    },
+  });
+
+  return fake(factory, options, objectWithIdComparisonFunction);
 }

packages/falso/src/lib/superhero.ts

@@ -1,4 +1,9 @@
-import { fake, FakeOptions, randElement } from './core/core';
+import {
+  fake,
+  FakeOptions,
+  objectWithIdComparisonFunction,
+  randElement,
+} from './core/core';
 import { data } from './superhero.json';
 import { randUuid } from './uuid';
 
@@ -50,5 +55,5 @@ export function randSuperhero<Options extends SuperheroOptions = never>(
     };
   };
 
-  return fake(factory, options);
+  return fake(factory, options, objectWithIdComparisonFunction);
 }

packages/falso/src/lib/user.ts

@@ -1,4 +1,4 @@
-import { fake, FakeOptions } from './core/core';
+import { fake, FakeOptions, objectWithIdComparisonFunction } from './core/core';
 import { randUuid } from './uuid';
 import { randEmail } from './email';
 import { randFirstName } from './first-name';
@@ -40,7 +40,7 @@ export interface User {
 export function randUser<Options extends FakeOptions = never>(
   options?: Options
 ) {
-  return fake(() => {
+  const factory = () => {
     const firstName = randFirstName({ withAccents: false });
     const lastName = randLastName({ withAccents: false });
 
@@ -56,5 +56,7 @@ export function randUser<Options extends FakeOptions = never>(
     };
 
     return user;
-  }, options);
+  };
+
+  return fake(factory, options, objectWithIdComparisonFunction);
 }