Fix unwatch multiple signals

src/wrapper.ts

@@ -227,28 +227,25 @@ export namespace Signal {
         const node = this[NODE];
         assertConsumerNode(node);
 
-        let indicesToShift = [];
-        for (let i = 0; i < node.producerNode.length; i++) {
+        for (let i = node.producerNode.length - 1; i >= 0; i--) {
           if (signals.includes(node.producerNode[i].wrapper)) {
             producerRemoveLiveConsumerAtIndex(node.producerNode[i], node.producerIndexOfThis[i]);
-            indicesToShift.push(i);
-          }
-        }
-        for (const idx of indicesToShift) {
-          // Logic copied from producerRemoveLiveConsumerAtIndex, but reversed
-          const lastIdx = node.producerNode!.length - 1;
-          node.producerNode![idx] = node.producerNode![lastIdx];
-          node.producerIndexOfThis[idx] = node.producerIndexOfThis[lastIdx];
-
-          node.producerNode.length--;
-          node.producerIndexOfThis.length--;
-          node.nextProducerIndex--;
-
-          if (idx < node.producerNode.length) {
-            const idxConsumer = node.producerIndexOfThis[idx];
-            const producer = node.producerNode[idx];
-            assertProducerNode(producer);
-            producer.liveConsumerIndexOfThis[idxConsumer] = idx;
+
+            // Logic copied from producerRemoveLiveConsumerAtIndex, but reversed
+            const lastIdx = node.producerNode!.length - 1;
+            node.producerNode![i] = node.producerNode![lastIdx];
+            node.producerIndexOfThis[i] = node.producerIndexOfThis[lastIdx];
+
+            node.producerNode.length--;
+            node.producerIndexOfThis.length--;
+            node.nextProducerIndex--;
+
+            if (i < node.producerNode.length) {
+              const idxConsumer = node.producerIndexOfThis[i];
+              const producer = node.producerNode[i];
+              assertProducerNode(producer);
+              producer.liveConsumerIndexOfThis[idxConsumer] = i;
+            }
           }
         }
       }

tests/Signal/subtle/watch-unwatch.test.ts

@@ -1,4 +1,4 @@
-import {describe, expect, it} from 'vitest';
+import {describe, expect, it, vi} from 'vitest';
 import {Signal} from '../../../src/wrapper.js';
 
 describe('watch and unwatch', () => {
@@ -160,4 +160,34 @@ describe('watch and unwatch', () => {
     expect(w.getPending()).toStrictEqual([]);
     expect(d).toBe(4);
   });
+  it('can unwatch multiple signals', async () => {
+    const signals = [...Array(7)].map((_, i) => new Signal.State(i));
+    const notify = vi.fn();
+    const watcher = new Signal.subtle.Watcher(notify);
+    const expectSources = (expected: typeof signals) => {
+      const sources = Signal.subtle.introspectSources(watcher) as typeof signals;
+      sources.sort((a, b) => signals.indexOf(a) - signals.indexOf(b));
+      expected.sort((a, b) => signals.indexOf(a) - signals.indexOf(b));
+      return expect(sources).toEqual(expected);
+    };
+
+    watcher.watch(...signals);
+    expectSources(signals);
+
+    const unwatched = [0, 3, 4, 6].map((i) => signals[i]);
+    const watched = signals.filter((s) => !unwatched.includes(s));
+
+    watcher.unwatch(...unwatched);
+    expectSources(watched);
+
+    let expectedNotifyCalls = 0;
+    for (const signal of signals) {
+      signal.set(signal.get() + 1);
+      if (watched.includes(signal)) ++expectedNotifyCalls;
+
+      expect(notify).toHaveBeenCalledTimes(expectedNotifyCalls);
+
+      watcher.watch();
+    }
+  });
 });