Babel decorator runtime helper errors for class with overloaded method

Please paste the output of ember -v here

ember-cli: 3.7.1 node: 10.11.0 os: darwin x64

Please paste the output of tsc -v here

Version 3.3.3333

Please paste your tconfig.json and tslint.json or eslint.json (if applicable) below

My tsconfig.json

{
“compilerOptions”: {
“target”: “es2017”,
“allowJs”: true,
“moduleResolution”: “node”,
“allowSyntheticDefaultImports”: true,
“noImplicitAny”: true,
“noImplicitThis”: true,
“alwaysStrict”: true,
“strictNullChecks”: true,
“strictPropertyInitialization”: true,
“noFallthroughCasesInSwitch”: true,
“noUnusedLocals”: true,
“noUnusedParameters”: true,
“noImplicitReturns”: true,
“noEmitOnError”: false,
“noEmit”: true,
“inlineSourceMap”: true,
“inlineSources”: true,
“baseUrl”: “.”,
“module”: “es6”,
“experimentalDecorators”: true,
“paths”: {
“ember-typescript-overloads-decorators-bug/tests/": [
"tests/”
],
“ember-typescript-overloads-decorators-bug/": [
"app/”
],
“": [
"types/”
]
}
},
“include”: [
“app//*",
"tests//",
"types/**/”
]
}

What are instructions we can follow to reproduce the issue?

git clone https://github.com/simonihmig/ember-typescript-overloads-decorators-bug

Reproduction Case

See the above reproduction repo.

Now about that bug. What did you expect to see?

Hit http://localhost:4200/ and see the default welcome page.

What happened instead?

Runtime error: Uncaught TypeError: Duplicated element (foo)

This happens when a TS class has at least one decorator and one overloaded method. Seems to be an issue with how the decorators and TS Babel plugins interact AFAICT.

The transpiled output of https://github.com/simonihmig/ember-typescript-overloads-decorators-bug/blob/master/app/controllers/application.ts looks like this:

let ApplicationController = (0, _decorate2.default)(null, function (_initialize, _EmberController) {
    class ApplicationController extends _EmberController {
      constructor(...args) {
        super(...args);

        _initialize(this);
      }

    }

    return {
      F: ApplicationController,
      d: [{
        kind: "field",
        decorators: [_service.inject],
        key: "router",
        value: void 0
      }, {
        kind: "field",
        key: "foo",
        value: void 0
      }, {
        kind: "field",
        key: "foo",
        value: void 0
      }, {
        kind: "method",
        key: "foo",
        value: function foo() {// dummy
        }
      }]
    };
  }, Ember.Controller);

So the overloaded foo method, which should affect only the typing, not the runtime code, causes multiple foo fields to be defined for the decorator runtime (@babel/runtime/helpers/esm/decorate), which then errors because of this.

[lifeart]

Maybe related to https://github.com/ember-cli/ember-ajax/issues/428

[pzuraq]

See the latest revision of https://github.com/emberjs/rfcs/pull/440 for more details