fix(overmind): fix disposing of derived during hot reloading

Author: christianalfoni

packages/node_modules/overmind/src/derived.ts

@@ -16,8 +16,16 @@ export class Derived {
   private value: any
   private paths: Set<string>
   private updateCount: number = 0
+  private disposeOnMutation: () => {}
   constructor(private cb: (state: object, parent: object) => void) {
-    return this.evaluate.bind(this)
+    const boundEvaluate: any = this.evaluate.bind(this)
+
+    boundEvaluate.dispose = () => {
+      this.disposeOnMutation()
+      this.trackStateTree.dispose()
+    }
+
+    return boundEvaluate
   }
   evaluate(
     eventHub: EventEmitter<Events>,
@@ -35,23 +43,25 @@ export class Derived {
       )
 
       this.scope = () => this.cb(parent, this.trackStateTree.state)
-      proxyStateTree.onMutation((_, paths, flushId) => {
-        if (this.isDirty) {
-          return
-        }
-
-        for (let mutationPath of paths) {
-          if (this.paths.has(mutationPath)) {
-            this.isDirty = true
-            eventHub.emitAsync(EventType.DERIVED_DIRTY, {
-              derivedPath: path,
-              path: mutationPath,
-              flushId,
-            })
+      this.disposeOnMutation = proxyStateTree.onMutation(
+        (_, paths, flushId) => {
+          if (this.isDirty) {
             return
           }
+
+          for (let mutationPath of paths) {
+            if (this.paths.has(mutationPath)) {
+              this.isDirty = true
+              eventHub.emitAsync(EventType.DERIVED_DIRTY, {
+                derivedPath: path,
+                path: mutationPath,
+                flushId,
+              })
+              return
+            }
+          }
         }
-      })
+      )
     }
 
     if (

packages/node_modules/overmind/src/index.ts

@@ -194,6 +194,7 @@ export class Overmind<ThisConfig extends IConfiguration>
   private nextExecutionId: number = 0
   private mode: DefaultMode | TestMode | SSRMode
   private originalConfiguration
+  private derivedReferences: Derived[] = []
   initialized: Promise<any>
   eventHub: EventEmitter<Events>
   devtools: Devtools
@@ -792,6 +793,10 @@ export class Overmind<ThisConfig extends IConfiguration>
         aggr[key] = this.processState(value)
       } else if (typeof value === 'function') {
         aggr[key] = new Derived(value)
+
+        if (IS_DEVELOPMENT) {
+          this.derivedReferences.push(aggr[key])
+        }
       } else {
         Object.defineProperty(aggr, key, originalDescriptor as any)
       }
@@ -832,6 +837,9 @@ export class Overmind<ThisConfig extends IConfiguration>
     return this.proxyStateTree.onFlush(cb)
   }
   reconfigure(configuration: IConfiguration) {
+    this.derivedReferences.forEach((derived) => {
+      derived.dispose()
+    })
     const mergedConfiguration = {
       ...configuration,
       state: mergeState(