resolving issue with the internal registration of the lwc

packages/lwc-engine/src/framework/__tests__/wc-test.ts

@@ -0,0 +1,12 @@
+import { Element } from "../main";
+import { customElement } from "../wc";
+
+describe('wc', () => {
+
+    it('should create a new constructor from LWCElement', () => {
+        class MyComponent extends Element {}
+        const WC = customElement(MyComponent);
+        expect(typeof WC).toBe('function');
+    });
+
+});

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

@@ -1,4 +1,4 @@
-import { getComponentDef } from "./def";
+import { getComponentDef, registerComponent } from "./def";
 import { ComponentConstructor } from "./component";
 import { keys, isUndefined, ArrayPush } from "./language";
 import { invokeComponentAttributeChangedCallback } from "./invoker";
@@ -10,6 +10,7 @@ import { getPropNameFromAttrName, getAttrNameFromPropName } from "./utils";
 export function customElement(Ctor: ComponentConstructor): Function {
     const def = getComponentDef(Ctor);
     const attrs = keys(def.observedAttrs);
+    let mustBeRegistered = true;
     if (process.env.NODE_ENV !== 'production') {
         assert.isTrue(isUndefined(Ctor.forceTagName), `The experimental support for web components does not include the support for \`static forceTagName\` to "${Ctor.forceTagName}" declaration in the class definition for ${Ctor}.`);
         // adding attributes that cannot be reflected into attributes
@@ -23,7 +24,12 @@ export function customElement(Ctor: ComponentConstructor): Function {
     return class extends HTMLElement {
         constructor() {
             super();
-            createVM(this.tagName.toLocaleLowerCase(), this);
+            const tagName = this.tagName.toLocaleLowerCase();
+            if (mustBeRegistered) {
+                mustBeRegistered = false;
+                registerComponent(tagName, Ctor);
+            }
+            createVM(tagName, this);
         }
         connectedCallback() {
             const vm = getCustomElementVM(this);