Revert "refactor(engine): locker does not longer need to leak base co…

…nstructor (#509)" (#510)

This reverts commit fa25e8a.

packages/lwc-engine/src/framework/__tests__/def.spec.ts

@@ -331,17 +331,5 @@ describe('def', () => {
             // make sure it picks the props from LightingElement
             expect(getComponentDef(B).props.title).toBeDefined();
         });
-
-        it('should allow escape hatch for Locker and other systems to provide their own base class to mimic LightningElement', () => {
-            // circular artifact for LightingElement
-            function CircularA() {
-                return CircularA; // because it returns itself, the engine knows what to do.
-            }
-            CircularA.__circular__ = true;
-
-            class B extends CircularA {}
-            // make sure it picks the props from LightingElement
-            expect(getComponentDef(B).props.title).toBeDefined();
-        });
     });
 });

packages/lwc-engine/src/framework/component.ts

@@ -6,7 +6,7 @@ import {
     vmBeingRendered,
     invokeEventListener,
 } from "./invoker";
-import { isArray, ArrayIndexOf, ArraySplice, isFunction, isUndefined } from "../shared/language";
+import { isArray, ArrayIndexOf, ArraySplice, isObject, isFunction, isUndefined } from "../shared/language";
 import { invokeServiceHook, Services } from "./services";
 import { PropsDef, WireHash } from './def';
 import { VM } from "./vm";
@@ -37,8 +37,9 @@ export function createComponent(vm: VM, Ctor: ComponentConstructor) {
     }
     // create the component instance
     invokeComponentConstructor(vm, Ctor);
-    if (isUndefined(vm.component)) {
-        throw new ReferenceError(`Invalid construction for ${vm}, you must extend LightningElement.`);
+
+    if (process.env.NODE_ENV !== 'production') {
+        assert.isTrue(isObject(vm.component), `Invalid construction for ${vm}, maybe you are missing the call to super() on classes extending Element.`);
     }
 }
 

packages/lwc-engine/src/framework/def.ts

@@ -95,17 +95,8 @@ import { patchLightningElementPrototypeWithRestrictions } from "./restrictions";
 const CtorToDefMap: WeakMap<any, ComponentDef> = new WeakMap();
 
 function getCtorProto(Ctor: any): any {
-    let proto = getPrototypeOf(Ctor);
-    // covering the cases where the ref is circular in AMD
-    if (isCircularModuleDependency(proto)) {
-        const p = resolveCircularModuleDependency(proto);
-        // escape hatch for Locker and other abstractions to provide their own base class instead
-        // of our Base class without having to leak it to user-land. If the circular function returns
-        // itself, that's the signal that we have hit the end of the proto chain, which must always
-        // be base.
-        proto = p === proto ? BaseElement : p;
-    }
-    return proto;
+    const proto = getPrototypeOf(Ctor);
+    return isCircularModuleDependency(proto) ? resolveCircularModuleDependency(proto) : proto;
 }
 
 // According to the WC spec (https://dom.spec.whatwg.org/#dom-element-attachshadow), certain elements