Handle readonly arrays for isNonEmptyArray guard. (#41)

Thinkmill · Mar 22, 2023 · 3b73321 · 3b73321 · vercel · Mar 22, 2023
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diff --git a/.changeset/olive-dryers-destroy.md b/.changeset/olive-dryers-destroy.md
@@ -0,0 +1,5 @@
+---
+'emery': patch
+---
+
+Handle readonly arrays for `isNonEmptyArray` guard.
diff --git a/src/guards.test.ts b/src/guards.test.ts
@@ -65,7 +65,9 @@ describe('guards', () => {
   describe('array', () => {
     it('isNonEmptyArray should validate assumed values', () => {
       expect(isNonEmptyArray([1, 2])).toBe(true);
+      expect(isNonEmptyArray([1, 2] as const)).toBe(true);
       expect(isNonEmptyArray([])).toBe(false);
+      expect(isNonEmptyArray([] as const)).toBe(false);
     });
   });
 

diff --git a/src/guards.ts b/src/guards.ts
@@ -33,7 +33,7 @@ export function isUndefined(value: unknown): value is undefined {
 // ------------------------------
 
 /** Checks whether or not an array is empty. */
-export function isNonEmptyArray<T>(value: T[]): value is [T, ...T[]] {
+export function isNonEmptyArray<T>(value: readonly T[]): value is [T, ...T[]] {
   return value.length > 0;
 }