fix(reactivity): cleanup subsHead in DEV + remove dep from depsMap during remove sub

Author: edison1105

packages/reactivity/src/dep.ts

@@ -82,6 +82,11 @@ export class Dep {
    */
   subsHead?: Link
 
+  /**
+   * Delete itself from depsMap
+   */
+  cleanup?: () => void
+
   constructor(public computed?: ComputedRefImpl | undefined) {
     if (__DEV__) {
       this.subsHead = undefined
@@ -249,6 +254,7 @@ export function track(target: object, type: TrackOpTypes, key: unknown): void {
     let dep = depsMap.get(key)
     if (!dep) {
       depsMap.set(key, (dep = new Dep()))
+      dep.cleanup = () => depsMap.delete(key)
     }
     if (__DEV__) {
       dep.track({

packages/reactivity/src/effect.ts

@@ -414,14 +414,22 @@ function removeSub(link: Link) {
     dep.subs = prevSub
   }
 
-  if (!dep.subs && dep.computed) {
+  if (!dep.subs) {
     // last subscriber removed
     // if computed, unsubscribe it from all its deps so this computed and its
     // value can be GCed
-    dep.computed.flags &= ~EffectFlags.TRACKING
-    for (let l = dep.computed.deps; l; l = l.nextDep) {
-      removeSub(l)
+    if (dep.computed) {
+      dep.computed.flags &= ~EffectFlags.TRACKING
+      for (let l = dep.computed.deps; l; l = l.nextDep) {
+        removeSub(l)
+      }
     }
+
+    // cleanup subsHead
+    if (__DEV__ && prevSub === undefined) dep.subsHead = undefined
+
+    // remove the dep from depsMap
+    if (dep.cleanup) dep.cleanup()
   }
 }