fix(theme-common): add a missing generic constraint (#7648)

packages/docusaurus-theme-common/src/utils/__tests__/reactUtils.test.ts

@@ -27,9 +27,12 @@ describe('useShallowMemoObject', () => {
     const someArray = ['hello', 'world'];
 
     const obj1 = {a: 1, b: '2', someObj, someArray};
-    const {result, rerender} = renderHook((val) => useShallowMemoObject(val), {
+    const {result, rerender} = renderHook<object, object>(
+      (val) => useShallowMemoObject(val),
+      {
         initialProps: obj1,
-    });
+      },
+    );
     expect(result.current).toBe(obj1);
 
     const obj2 = {a: 1, b: '2', someObj, someArray};
@@ -40,17 +43,31 @@ describe('useShallowMemoObject', () => {
     rerender(obj3);
     expect(result.current).toBe(obj1);
 
-    // Current implementation is basic and sensitive to order
     const obj4 = {b: '2', a: 1, someObj, someArray};
     rerender(obj4);
-    expect(result.current).toBe(obj4);
+    expect(result.current).toBe(obj1);
 
     const obj5 = {b: '2', a: 1, someObj, someArray};
     rerender(obj5);
-    expect(result.current).toBe(obj4);
+    expect(result.current).toBe(obj1);
 
-    const obj6 = {b: '2', a: 1, someObj: {...someObj}, someArray};
+    const obj6 = {b: 1, a: '2', someObj, someArray};
     rerender(obj6);
     expect(result.current).toBe(obj6);
+    expect(result.current).not.toBe(obj5);
+
+    const obj7 = {b: 1, a: '2', someObj: {...someObj}, someArray};
+    rerender(obj7);
+    expect(result.current).toBe(obj7);
+    expect(result.current).not.toBe(obj6);
+
+    const obj8 = {...obj7};
+    rerender(obj8);
+    expect(result.current).toBe(obj7);
+
+    const obj9 = {...obj7, another: true};
+    rerender(obj9);
+    expect(result.current).toBe(obj9);
+    expect(result.current).not.toBe(obj7);
   });
 });

packages/docusaurus-theme-common/src/utils/reactUtils.tsx

@@ -76,21 +76,17 @@ export class ReactContextError extends Error {
 }
 
 /**
- * Shallow-memoize an object
+ * Shallow-memoize an object. This means the returned object will be the same as
- *
+ * the previous render if the property keys and values did not change. This
- * This means the returned object will be the same as the previous render
+ * works for simple cases: when property values are primitives or stable
- * if the attribute names and identities did not change.
+ * objects.
- *
- * This works for simple cases: when attributes are primitives or stable objects
  *
  * @param obj
  */
-export function useShallowMemoObject<O>(obj: O): O {
+export function useShallowMemoObject<O extends object>(obj: O): O {
-  return useMemo(
+  const deps = Object.entries(obj);
-    () => obj,
+  // Sort by keys to make it order-insensitive
-    // Is this safe?
+  deps.sort((a, b) => a[0].localeCompare(b[0]));
-    // TODO make this implementation not order-dependent?
   // eslint-disable-next-line react-hooks/exhaustive-deps
-    [...Object.keys(obj), ...Object.values(obj)],
+  return useMemo(() => obj, deps.flat());
-  );
 }