WebStorm, An async function or method in ES5/ES3 requires the 'Promise' constructor

12
votes

I try to write tests in typescript (ES6) using WebStorm IDE. E.g.: 

// Imports...

describe('Message', () => {
    const server = express();
    server.use(bodyParser.json());

    const messageService = { findAll: () => ['test'] };

    beforeAll(async () => {
        const module = await Test.createTestingModule({
            modules: [MessageModule],
        })...
    });

    // Tests...
});

However WebStorm IDE shows following error at async () =>

TS2705: An async function or method in ES5/ES3 requires the Promise constructor. Make sure you have a declaration for the Promise constructor or include ES2015 in your --lib option.

My tsconfig.json:

{
  "compilerOptions": {
    "module": "commonjs",
    "declaration": false,
    "noImplicitAny": false,
    "removeComments": true,
    "noLib": false,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "target": "es6",
    "sourceMap": true,
    "allowJs": true,
    "outDir": "./dist"
  },
  "include": [
    "src/**/*"
  ],
  "exclude": [
    "node_modules",
    "**/*.spec.ts"
  ]
}

I read ts An async function or method in ES5/ES3 requires the 'Promise' constructor and tried adding 

"lib": [ "es2015" ]

however it does not have any effect. Any ideas what's wrong?

4
typescriptasync-awaitwebstorm
I added this and still this is giving me errors in normal source files. What can be wrong? This is giving me this error in dynamic imports - Ajay Gaur
Also, I'm using awesome-typescript-loader as typescript loader - Ajay Gaur

4 Answers

19
votes

Adding

"lib": [ "es2015" ]

to tsconfig.json should fix the issue. However it seems that your spec files are not included in your tsconfig.json (check "include":[] and "exclude":[] values). So the Typescript service must be using a different tsconfig.json for your files (may be a default one, if no tsconfig.json files that include your specs can be found) To fix the issue, make sure to specify the lib property in config that is used for your spec files processing

19
votes

Solution without editing the project sources

I had this problem with IntelliJ and resolved by changing my IDE settings:

Settings -> Language & Frameworks -> TypeScript

then in the "Options" field add:

--lib es2015

enter image description here

0
votes
{
  "compilerOptions": {
    "module": "commonjs",
    "declaration": true,
    "noImplicitAny": false,
    "removeComments": true,
    "noLib": false,
    "allowSyntheticDefaultImports": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "target": "es6",
    "sourceMap": true,
    "outDir": "./dist",
    "baseUrl": "./src",
    "lib": ["es2015"]
  },
  "include": [
    "src/**/*",
    "**/*.spec.ts"
  ],
  "exclude": [
    "node_modules"
  ]
}

adding "lib":["es2015"] to "compilerOptions" as per @lena's answer and Removing **/*.spec.ts from "exclude":[] and adding it to "include":[] solved it for me.

-1
votes

Add "lib": [ "es2015" ] in tsconfig.json under compilerOptions as

{
    "compilerOptions": {
      "lib": [ "es2015" ]
  }
}