perf(commands): skip no-op dispatch emissions

commands/dispatcher.test.ts

@@ -1,10 +1,17 @@
 import { describe, expect, test } from "bun:test";
+import type { Command } from "./command";
 import { createInitialAppState } from "@editor/initial-state";
 import { createAppStore } from "@editor/store";
 import { commandIds } from "./ids";
 import { createCommandRegistry } from "./registry";
 import { viewportPanCommand } from "./viewport";
 
+const noOpCommand: Command<unknown> = {
+  id: "test.noop",
+  name: "No-op",
+  execute: ({ state }) => state,
+};
+
 describe("command dispatcher", () => {
   test("throws for unknown commands", () => {
     const store = createAppStore(createInitialAppState("Test"), createCommandRegistry([]));
@@ -16,4 +23,23 @@ describe("command dispatcher", () => {
     store.dispatch(commandIds.viewportPan, { delta: { x: 3, y: 7 } });
     expect(store.getState().editor.viewport.center).toEqual({ x: 3, y: 7 });
   });
+
+  test("repeated no-op commands do not emit or record history", () => {
+    const initialState = createInitialAppState("Test");
+    const store = createAppStore(initialState, createCommandRegistry([noOpCommand]));
+    let notificationCount = 0;
+    store.subscribe(() => {
+      notificationCount += 1;
+    });
+
+    const firstResult = store.dispatch("test.noop" as never, undefined as never);
+    const secondResult = store.dispatch("test.noop" as never, undefined as never);
+
+    expect(firstResult).toBe(initialState);
+    expect(secondResult).toBe(initialState);
+    expect(store.getState()).toBe(initialState);
+    expect(store.getState().history.past).toHaveLength(0);
+    expect(store.getState().history.future).toHaveLength(0);
+    expect(notificationCount).toBe(0);
+  });
 });

commands/dispatcher.ts

@@ -25,6 +25,9 @@ export function createCommandDispatcher(options: {
       const currentState = options.getState();
       const context: CommandContext = { state: currentState };
       const executedState = command.execute(context, payload);
+      if (executedState === currentState) {
+        return currentState;
+      }
       const nextState = shouldRecordHistory(commandId, currentState, executedState) ? recordHistory(currentState, executedState) : executedState;
       options.setState(nextState);
       return nextState;