fix: handle null and undefined in @fluentui/utilities shallowCompare (m…

…icrosoft#25623)

change/@fluentui-utilities-6d708b55-ae70-43d3-bae5-d23b00ab9b73.json

@@ -0,0 +1,7 @@
+{
+ "type": "patch",
+ "comment": "fix: handle null and undefined in shallowCompare, add tests",
+ "packageName": "@fluentui/utilities",
+ "email": "sarah.higley@microsoft.com",
+ "dependentChangeType": "patch"
+}

packages/utilities/src/object.test.ts

@@ -1,4 +1,73 @@
-import { assign, filteredAssign, mapEnumByName, values, omit } from './object';
+import { assign, filteredAssign, mapEnumByName, values, omit, shallowCompare } from './object';
+
+describe('shallowCompare', () => {
+ it('returns true for matching objects', () => {
+ const a = {
+ a: 1,
+ b: 'string',
+ c: {
+ d: 2,
+ },
+ };
+
+ const b = { ...a };
+
+ expect(shallowCompare(a, b)).toBeTruthy();
+ });
+
+ it('returns false when one object is a superset of the other', () => {
+ // eslint-disable-next-line @typescript-eslint/no-explicit-any
+ const a: { [key: string]: any } = {
+ a: 1,
+ b: 'string',
+ c: {
+ d: 2,
+ },
+ };
+
+ const b = { ...a, e: 'extra' };
+
+ expect(shallowCompare(a, b)).toBeFalsy();
+
+ a.e = 'extra';
+ a.f = 3;
+
+ expect(shallowCompare(a, b)).toBeFalsy();
+ });
+
+ it('returns false when nested objects are not strictly equal', () => {
+ // eslint-disable-next-line @typescript-eslint/no-explicit-any
+ const a: { [key: string]: any } = {
+ a: 1,
+ b: 'string',
+ c: {
+ d: 2,
+ },
+ };
+
+ const b = { ...a, c: { ...a.c } };
+
+ expect(shallowCompare(a, b)).toBeFalsy();
+ });
+
+ it('returns true for two empty objects', () => {
+ expect(shallowCompare({}, {})).toBeTruthy();
+ });
+
+ it('returns true for two falsy values', () => {
+ expect(shallowCompare(null, null)).toBeTruthy();
+ expect(shallowCompare(undefined, undefined)).toBeTruthy();
+ expect(shallowCompare(null, undefined)).toBeTruthy();
+ expect(shallowCompare(0, '')).toBeTruthy();
+ expect(shallowCompare(null, '')).toBeTruthy();
+ expect(shallowCompare(0, undefined)).toBeTruthy();
+ });
+
+ it('returns false when comparing null or undefined against an object', () => {
+ expect(shallowCompare(null, { a: 1 })).toBeFalsy();
+ expect(shallowCompare(undefined, { a: 1 })).toBeFalsy();
+ });
+});
 
 describe('assign', () => {
  it('can copy an object', () => {

packages/utilities/src/object.ts

@@ -5,6 +5,11 @@
  */
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 export function shallowCompare<TA extends any, TB extends any>(a: TA, b: TB): boolean {
+ if (!a || !b) {
+ // only return true if both a and b are falsy
+ return !a && !b;
+ }
+
  for (let propName in a) {
  if ((a as Object).hasOwnProperty(propName)) {
  if (!(b as Object).hasOwnProperty(propName) || (b as { [key: string]: unknown })[propName] !== a[propName]) {