Get: Fix handling of readonly array (#799)

sindresorhus · Jan 21, 2024 · 4a38651 · 4a38651
1 parent 6f1db93
commit 4a38651
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Showing 2 changed files with 10 additions and 2 deletions.
diff --git a/source/get.d.ts b/source/get.d.ts
@@ -17,7 +17,7 @@ type GetOptions = {
 Like the `Get` type but receives an array of strings as a path parameter.
 */
 type GetWithPath<BaseType, Keys extends readonly string[], Options extends GetOptions = {}> =
-	Keys extends []
+	Keys extends readonly []
 		? BaseType
 		: Keys extends readonly [infer Head, ...infer Tail]
 			? GetWithPath<
@@ -125,7 +125,7 @@ type PropertyOf<BaseType, Key extends string, Options extends GetOptions = {}> =
 		? undefined
 		: Key extends keyof BaseType
 			? StrictPropertyOf<BaseType, Key, Options>
-			: BaseType extends [] | [unknown, ...unknown[]]
+			: BaseType extends readonly [] | readonly [unknown, ...unknown[]]
 				? unknown // It's a tuple, but `Key` did not extend `keyof BaseType`. So the index is out of bounds.
 				: BaseType extends {
 					[n: number]: infer Item;

diff --git a/test-d/get.ts b/test-d/get.ts
@@ -132,3 +132,11 @@ expectTypeOf<Get<WithDictionary, 'foo.whatever'>>().toEqualTypeOf<{bar: number}
 expectTypeOf<Get<WithDictionary, 'foo.whatever.bar'>>().toEqualTypeOf<number | undefined>();
 expectTypeOf<Get<WithDictionary, 'baz.whatever.qux[3].x'>>().toEqualTypeOf<boolean | undefined>();
 expectTypeOf<Get<WithDictionary, ['baz', 'whatever', 'qux', '3', 'x']>>().toEqualTypeOf<boolean | undefined>();
+
+// Test array index out of bounds
+expectTypeOf<Get<{a: []}, 'a[0]'>>().toEqualTypeOf<unknown>();
+expectTypeOf<Get<{a: readonly []}, 'a[0]'>>().toEqualTypeOf<unknown>();
+
+// Test empty path array
+expectTypeOf<WithDictionary>().toEqualTypeOf<Get<WithDictionary, []>>();
+expectTypeOf<WithDictionary>().toEqualTypeOf<Get<WithDictionary, readonly []>>();