fix-next(Angular): HMR for lazy loaded NgModules (#759)

* fix-next(Angular): HMR for lazy loaded NgModules

Currently, the `lazy-ngmodule-hot-loader` [adds](6a9db32) a HMR self-accept to every lazy loaded NgModule during build.

After [alignment](fe4abfb) of the HMR lifecycle of NativeScript Angular with non-Angular applications, it requires a handler to update the app after module replacement.

* refactor: minor tweaks

* Apply suggestions from code review

Co-Authored-By: vchimev <[email protected]>

Author: vchimev

Diff for: lazy-ngmodule-hot-loader.js

@@ -1,7 +1,20 @@
 const { safeGet } = require("./projectHelpers");
 
 const LAZY_RESOURCE_CONTEXT = "$$_lazy_route_resource";
-const HOT_SELF_ACCEPT = "module.hot && module.hot.accept()";
+const HOT_SELF_ACCEPT = "module.hot.accept();";
+const HOT_DISPOSE = `
+module.hot.dispose(() => {
+    // Currently the context is needed only for application style modules.
+    const moduleContext = "{}";
+    global.__hmrRefresh(moduleContext);
+});
+`;
+const HMR_HANDLER = `
+    if (module.hot) {
+        ${HOT_SELF_ACCEPT}
+        ${HOT_DISPOSE}
+    }
+`;
 
 const isLazyLoadedNgModule = resource => {
     const issuer = safeGet(resource, "issuer");
@@ -12,6 +25,6 @@ const isLazyLoadedNgModule = resource => {
 
 module.exports = function (source) {
     return isLazyLoadedNgModule(this._module) ?
-        `${source};${HOT_SELF_ACCEPT}`:
+        `${source};${HMR_HANDLER}` :
         source;
 };