fix(proxy-state-tree): evaluate functions when setting them

Author: christianalfoni

packages/node_modules/overmind/src/derived.test.ts

@@ -136,6 +136,7 @@ describe('Derived', () => {
     app.actions.addDerived()
     expect(app.state.upperFoo).toBe('BAR')
     app.actions.changeFoo()
+    
     expect(app.state.upperFoo).toBe('BAR2')
   })
 

packages/node_modules/overmind/src/derived.ts

@@ -13,7 +13,6 @@ export const IS_DERIVED = Symbol('IS_DERIVED')
 
 export class Derived {
   private isDirty: boolean = true
-  private trackStateTree: ITrackStateTree<any>
   private previousProxifier: any
   private value: any
   private paths: Set<string>
@@ -46,7 +45,6 @@ export class Derived {
     if (!this.disposeOnMutation) {
       this.disposeOnMutation = proxyStateTree.onMutation(
         (_, paths, flushId) => {
-          // It has been removed from the tree
           if (typeof path.reduce((aggr, key) => aggr && aggr[key], proxyStateTree.sourceState) !== 'function') {
             this.disposeOnMutation()
             return

packages/node_modules/proxy-state-tree/src/Proxyfier.ts

@@ -341,32 +341,33 @@ export class Proxifier {
         const mutationTree = proxifier.getMutationTree()
         const existingValue = target[prop]
 
+        // Adding functions is not considered mutations
         if (typeof value === 'function' && proxifier.tree.master.options.onFunction) {
           const result = proxifier.tree.master.options.onFunction(
-            proxifier.tree,
+            proxifier.getTrackingTree() || proxifier.tree,
             nestedPath,
             value
           )
 
           value = result.func
-        }
-
-        mutationTree.addMutation(
-          {
-            method: 'set',
-            path: nestedPath,
-            args: [value],
-            hasChangedValue: value !== target[prop],
-            revert: () => {
-              if (existingValue === undefined) {
-                delete proxy[prop]
-              } else {
-                proxy[prop] = existingValue
-              }
+        } else {
+          mutationTree.addMutation(
+            {
+              method: 'set',
+              path: nestedPath,
+              args: [value],
+              hasChangedValue: value !== target[prop],
+              revert: () => {
+                if (existingValue === undefined) {
+                  delete proxy[prop]
+                } else {
+                  proxy[prop] = existingValue
+                }
+              },
             },
-          },
-          objectChangePath
-        )
+            objectChangePath
+          )
+        }
 
         return Reflect.set(target, prop, value)
       },