fix(controller): stop element from inheriting scope

src/controller.js

@@ -33,7 +33,7 @@ export class Controller {
     this.isAttached = false;
     this.view = null;
     this.isBound = false;
-    this.bindingContext = null;
+    this.scope = null;
 
     let observerLookup = behavior.observerLocator.getOrCreateObserversLookup(viewModel);
     let handlesBind = behavior.handlesBind;
@@ -71,7 +71,7 @@ export class Controller {
     this.view.overrideContext = overrideContext || createOverrideContext(this.viewModel);
     this.view._isUserControlled = true;
 
-    if(this.behavior.handlesCreated) {
+    if (this.behavior.handlesCreated) {
       this.viewModel.created(owningView || null, this.view);
     }
 
@@ -90,18 +90,17 @@ export class Controller {
     let x;
     let observer;
     let selfSubscriber;
-    let context = scope.bindingContext;
 
     if (this.isBound) {
-      if (this.bindingContext === context) {
+      if (this.scope === scope) {
         return;
       }
 
       this.unbind();
     }
 
     this.isBound = true;
-    this.bindingContext = context;
+    this.scope = scope;
 
     for (i = 0, ii = boundProperties.length; i < ii; ++i) {
       x = boundProperties[i];
@@ -120,14 +119,33 @@ export class Controller {
       observer.selfSubscriber = selfSubscriber;
     }
 
+    let overrideContext;
     if (this.view !== null) {
       if (skipSelfSubscriber) {
         this.view.viewModelScope = scope;
       }
-
-      this.view.bind(this.viewModel, createOverrideContext(this.viewModel, scope.overrideContext));
+      // do we need to create an overrideContext or is the scope's overrideContext
+      // valid for this viewModel?
+      if (this.viewModel === scope.overrideContext.bindingContext) {
+        overrideContext = scope.overrideContext;
+      // should we inherit the parent scope? (eg compose)
+      } else if (this.instruction.inheritBindingContext) {
+        overrideContext = createOverrideContext(this.viewModel, scope.overrideContext);
+      // create the overrideContext and capture the parent without making it
+      // available to AccessScope. We may need it later for template-part replacements.
+      } else {
+        overrideContext = createOverrideContext(this.viewModel);
+        overrideContext.__parentOverrideContext = scope.overrideContext;
+      }
+      this.view.bind(this.viewModel, overrideContext);
     } else if (skipSelfSubscriber) {
-      this.viewModel.bind(context, scope.overrideContext);
+      overrideContext = scope.overrideContext;
+      // replacing a template-part? Clone the overrideContext and connect the parent.
+      if (this.viewModel.viewFactory && this.viewModel.viewFactory.factoryCreateInstruction.partReplacements) {
+        overrideContext = Object.assign({}, scope.overrideContext);
+        overrideContext.parentOverrideContext = scope.overrideContext.__parentOverrideContext;
+      }
+      this.viewModel.bind(scope.bindingContext, overrideContext);
     }
   }
 

src/instructions.js

@@ -134,6 +134,7 @@ export class BehaviorInstruction {
     instruction.host = host;
     instruction.viewModel = viewModel;
     instruction.viewFactory = viewFactory;
+    instruction.inheritBindingContext = true;
     return instruction;
   }
 
@@ -154,6 +155,7 @@ export class BehaviorInstruction {
     this.attributes = null;
     this.type = null;
     this.attrName = null;
+    this.inheritBindingContext = false;
   }
 }