Compile decorators properly when googmodule is false and transformTypesToClosure is true

demo/decorators.ts

@@ -0,0 +1,21 @@
+export function classDecorator(constructor: Function) {
+  Object.seal(constructor);
+  Object.seal(constructor.prototype);
+}
+
+export function methodDecorator(value: boolean) {
+  return function (target: any, propertyKey: string, descriptor?: PropertyDescriptor) {
+    if (descriptor) {
+      descriptor.enumerable = value;
+    }
+  };
+}
+
+export function accessorDecorator(value: boolean,) {
+  return function (target: any, propertyKey: string, descriptor?: PropertyDescriptor) {
+    if (descriptor) {
+      descriptor.configurable = value;
+    }
+  };
+}
+

demo/tsconfig.json

@@ -7,6 +7,7 @@
     "strict": true,
     "moduleResolution": "Bundler",
     "esModuleInterop": true,
+    "experimentalDecorators": true,
   },
   "exclude": [
     "test.ts"

demo/using_decorators.ts

@@ -0,0 +1,28 @@
+import { accessorDecorator, classDecorator, methodDecorator } from "./decorators";
+
+@classDecorator
+export class Person {
+    private name_: string;
+    constructor(name: string) {
+        this.name_ = name;
+    }
+
+    @accessorDecorator(true)
+    get name() {
+        return this.name_;
+    }
+
+    @methodDecorator(true)
+    greet() {
+        console.log(`Hello, my name is ${this.name}.`);
+    }
+  }
+
+  const p = new Person("Ron");
+  p.greet();
+
+
+  export class Employee {
+    constructor(private age_: number) {}
+    get age() { return this.age_; }
+  }

src/decorator_downlevel_transformer.ts

@@ -530,6 +530,19 @@ export function decoratorDownlevelTransformer(
       if (decoratedProperties.size) {
         newMembers.push(createPropDecoratorsClassProperty(diagnostics, decoratedProperties));
       }
+      /**
+       * I'm pretty sure this is where the class ends up turning from
+       * 
+       * @classDecorator
+       * class Person { ... }
+       * 
+       * into
+       * 
+       * let Person = class Person { ... }
+       * Person = __decorate([
+       *    classDecorator
+       * ], Person);
+       */
       return ts.factory.updateClassDeclaration(
           classDecl, modifiersToKeep.length ? modifiersToKeep : undefined,
           classDecl.name, classDecl.typeParameters, classDecl.heritageClauses,

tsconfig.json

@@ -18,7 +18,8 @@
     "strict": true,
     "outDir": "out",
     "paths": {"tsickle": ["./src/tsickle.ts"]},
-    "esModuleInterop": true
+    "esModuleInterop": true,
+    "experimentalDecorators": true
   },
   "include": [
     "src/*.ts",