Angular2 Duplicate identifier 'PropertyKey'

Question

I am building an angular2 application using angular-cli. angular-in-memory-web-api was not installed by default.

So I searched

Answer 1

It seems like you are compiling in the node_modules folder, so, in your tsconfig.json (that I presume you have) make sure to set your exclusions for the compiler to ignore:

{
  "compileOnSave": true,
  "compilerOptions": {
    <...>
  },
  "exclude": [
    "node_modules"
  ] 
}

Answer 2

So I ran into this same issue when upgrading "target":"es5" to "target":"es6" I fixed it by upgrading my tsconfig.json:

From

{
  "compilerOptions": {
    "target": "es6",
    "module": "commonjs",
    "moduleResolution": "node",
    "sourceMap": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "removeComments": false,
    "noImplicitAny": false
  }
}

To

{
  "compilerOptions": {
    "target": "es6",
     "lib": ["dom", "es5"],
    "typeRoots": [
      "./node_modules/@types"
    ],
    "module": "commonjs",
    "moduleResolution": "node",
    "sourceMap": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "removeComments": false,
    "noImplicitAny": false
  },
  "exclude": [
    "node_modules",
    "dist"
  ],
  "compileOnSave": false
}

This blog article helped a lot.

This is caused by multiple versions of the same type definitions. In tsconfig.json we have es6 as part of the lib array but we also have core-js in node_modules/@types. The type definitions in core-js overlap with the ones already distributed with TypeScript. In order to fix this problem we have two options:

• Change es6 to es5 in compilerOptions’s lib property. This way TypeScript won’t include ES6 type definitions.
• Remove core-js from node_modules. This way TypeScript will use only its internal ES6 type definitions.