fix: return type when using empty records

fix #465
RebeccaStevens · May 20, 2024 · 6b4ff3f · 6b4ff3f
1 parent f4991d8
commit 6b4ff3f
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Showing 2 changed files with 26 additions and 11 deletions.
diff --git a/src/types/defaults.ts b/src/types/defaults.ts
@@ -68,17 +68,20 @@ type RecordPropertyMeta<
 
 type RecordsToRecordMeta<
   Ts extends ReadonlyArray<Record<PropertyKey, unknown>>,
-> = {
+> = FilterOutNever<{
   [I in keyof Ts]: RecordToRecordMeta<Ts[I]>;
-};
+}>;
 
-type RecordToRecordMeta<T extends Record<PropertyKey, unknown>> = {
-  [K in keyof T]-?: {
-    key: K;
-    value: Required<T>[K];
-    optional: KeyIsOptional<K, T>;
-  };
-};
+type RecordToRecordMeta<T extends Record<PropertyKey, unknown>> =
+  object extends T
+    ? never
+    : {
+        [K in keyof T]-?: {
+          key: K;
+          value: Required<T>[K];
+          optional: KeyIsOptional<K, T>;
+        };
+      };
 
 /**
  * Deep merge records.
@@ -98,10 +101,13 @@ export type DeepMergeRecordsDefaultHKT<
  * Deep merge record props.
  */
 type DeepMergeRecordMetaDefaultHKTProps<
-  RecordMetas extends ReadonlyArray<RecordMeta>,
+  RecordMetas,
   MF extends DeepMergeMergeFunctionsURIs,
   M,
-> = CreateRecordFromMeta<MergeRecordMeta<RecordMetas>, MF, M>;
+> =
+  RecordMetas extends ReadonlyArray<RecordMeta>
+    ? CreateRecordFromMeta<MergeRecordMeta<RecordMetas>, MF, M>
+    : never;
 
 type MergeRecordMeta<RecordMetas extends ReadonlyArray<RecordMeta>> =
   GroupValuesByKey<

diff --git a/tests/deepmerge.test-d.ts b/tests/deepmerge.test-d.ts
@@ -244,3 +244,12 @@ const q: Record<string, string> = { a: "a" };
 
 const test19 = deepmerge(q, q);
 expectType<Record<string, string>>(test19);
+
+const test20 = deepmerge({}, a);
+expectType<{
+  foo: string;
+  baz: {
+    quux: string[];
+  };
+  garply: number;
+}>(test20);