Add generic for object-merge type (#466)

angus-c · Jul 18, 2022 · 80b15e1 · 80b15e1
1 parent 1268d78
commit 80b15e1
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Showing 2 changed files with 13 additions and 1 deletion.
diff --git a/packages/object-merge/index.d.ts b/packages/object-merge/index.d.ts
@@ -1,3 +1,6 @@
 // Definitions by: nokazn <https://github.com/nokazn>
-declare function merge(obj1: object, ...objs: object[]): object;
+declare function merge<
+  TObj1 extends object = object,
+  TObjs extends object = object
+>(obj1: TObj1, ...objs: TObjs[]): TObj1 & TObjs;
 export default merge;
diff --git a/packages/object-merge/index.tests.ts b/packages/object-merge/index.tests.ts
@@ -9,6 +9,7 @@ merge([]);
 merge(() => {});
 merge(new Map());
 merge(new Set());
+merge<{ a: number; b: number; }>({ a: 1, b: 2 });
 
 // Multiple arguments
 merge({}, {});
@@ -18,6 +19,10 @@ merge({}, () => {});
 merge({}, new Map());
 merge({}, new Set());
 merge({}, { a: 1 }, { a: 2, b: 3 });
+merge<{ a: number; b: number; }, { a: number; b: number; c: number; }>(
+  { a: 4, b: 8 },
+  { a: 6, b: 1, c: 8 }
+);
 
 // Not OK
 
@@ -36,6 +41,8 @@ merge(null);
 merge(undefined);
 // @ts-expect-error
 merge(Symbol());
+// @ts-expect-error
+merge<{ a: string; b: string; }>({ a: 1, b: 2 });
 
 // Multiple arguments
 // @ts-expect-error
@@ -52,3 +59,5 @@ merge({}, undefined);
 merge({}, Symbol());
 // @ts-expect-error
 merge({}, {}, null);
+// @ts-expect-error
+merge<{ a: string; b: string; }, { a: string; b: string; c: string; }>({ a: 4, b: 8 }, { a: 6, b: 1, c: 8 });