fix(mergeDeep): handle undefined sources correctly (#7012)

* chore(release): update monorepo packages versions (#6826) Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com> * fix(mergeDeep): handle `undefined` sources correctly * Fix * Major * .. --------- Co-authored-by: TheGuildBot <59414373+theguild-bot@users.noreply.github.com> Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: 3 people

.changeset/chilly-icons-guess.md

@@ -0,0 +1,11 @@
+---
+'@graphql-tools/utils': patch
+---
+
+Fix the bug in `mergeDeep`;
+
+The following inputs and outputs are corrected;
+
+- `mergeDeep([{a:2}, undefined])` - Any nullish values should be ignored so it should return `{a:2}`
+- `mergeDeep([])` - no sources should return `undefined`
+- `mergeDeep([undefined])` - no sources should return `undefined`

packages/utils/src/mergeDeep.ts

@@ -12,6 +12,12 @@ export function mergeDeep<S extends any[]>(
  respectArrays = false,
  respectArrayLength = false,
 ): UnboxIntersection<UnionToIntersection<BoxedTupleTypes<S>>> & any {
+ if (sources.length === 0) {
+ return;
+ }
+ if (sources.length === 1) {
+ return sources[0];
+ }
  let expectedLength: number | undefined;
  let allArrays = true;
  const areArraysInTheSameLength = sources.every(source => {
@@ -46,14 +52,17 @@ export function mergeDeep<S extends any[]>(
  let firstObjectSource: any;
  if (respectPrototype) {
  firstObjectSource = sources.find(source => isObject(source));
- if (output == null) {
- output = {};
- }
  if (firstObjectSource) {
+ if (output == null) {
+ output = {};
+ }
  Object.setPrototypeOf(output, Object.create(Object.getPrototypeOf(firstObjectSource)));
  }
  }
  for (const source of sources) {
+ if (source == null) {
+ continue;
+ }
  if (isObject(source)) {
  if (firstObjectSource) {
  const outputPrototype = Object.getPrototypeOf(output);

packages/utils/tests/mergeDeep.test.ts

@@ -72,4 +72,16 @@ describe('mergeDeep', () => {
  const b = { options: ['$A', '$B'] };
  expect(mergeDeep([a, b], undefined, true, true)).toEqual({ options: ['$A', '$B'] });
  });
+
+ it('filters nullish values', () => {
+ expect(mergeDeep([{ a: 'dsa' }, { a: 'dd', b: 1 }, undefined])).toEqual({ a: 'dd', b: 1 });
+ });
+
+ it('respects empty objects', () => {
+ expect(mergeDeep([{}])).toEqual({});
+ });
+
+ it('returns undefined when an empty sources array passed', () => {
+ expect(mergeDeep([])).toEqual(undefined);
+ });
 });