Avoid excessive re-render when setting same reference/value in snapshot (#32918)

* perf: avoid excessive re-render when setting same value in snapshot

* test: update tests

apps/web/test/viewmodels/message-body/EventContentBodyViewModel-test.tsx

@@ -280,7 +280,7 @@ describe("EventContentBodyViewModel", () => {
         expect(vm.getSnapshot().body).toBe("Updated");
     });
 
-    it("emits updates when setters are called with unchanged values", () => {
+    it("doesn't emit updates when setters are called with unchanged values", () => {
         const replacer = jest.fn();
         mockedCombineRenderers.mockReturnValue(() => replacer);
         mockedBodyToNode.mockReturnValue({
@@ -298,7 +298,7 @@ describe("EventContentBodyViewModel", () => {
         vm.setEventContent(undefined, defaultContent);
         vm.setAs("span");
 
-        expect(subscriber).toHaveBeenCalledTimes(2);
+        expect(subscriber).toHaveBeenCalledTimes(0);
         expect(vm.getSnapshot()).toEqual(previousSnapshot);
     });
 

apps/web/test/viewmodels/message-body/ReactionsRowButtonViewModel-test.tsx

@@ -80,7 +80,7 @@ describe("ReactionsRowButtonViewModel", () => {
         expect(listener).toHaveBeenCalledTimes(1);
         expect(tooltipSetPropsSpy).not.toHaveBeenCalled();
 
-        vm.setCount(5);
+        vm.setCount(6);
 
         expect(listener).toHaveBeenCalledTimes(2);
     });

apps/web/test/viewmodels/message-body/ReactionsRowViewModel-test.tsx

@@ -86,7 +86,7 @@ describe("ReactionsRowViewModel", () => {
         expect(onAddReactionContextMenu).toHaveBeenCalledWith(clickEvent);
     });
 
-    it("emits only for setters that always merge when values are unchanged", () => {
+    it("doesn't emit only setters that always merge when values are unchanged", () => {
         const vm = createVm();
         const previousSnapshot = vm.getSnapshot();
         const listener = jest.fn();
@@ -99,7 +99,7 @@ describe("ReactionsRowViewModel", () => {
 
         // `setReactionGroupCount` is optimized and skips emit for unchanged derived values.
         // The other setters always merge and therefore emit.
-        expect(listener).toHaveBeenCalledTimes(3);
+        expect(listener).toHaveBeenCalledTimes(0);
         expect(vm.getSnapshot()).toEqual(previousSnapshot);
     });
 });