declaration-output-mapped-types

README.md

declaration-output-mapped-types

Demonstrates bug with declaration output of mapped types in TypeScript 2.3.4.

Usage:

• npm install
• npm run build
• Observe invalid syntax in dist/index.d.ts, which needs but lacks quotes around the keys in the declaration of scopes:

export declare const scopes: {
    noun:verb: "noun:verb";
    verb:adjective: "verb:adjective";
    noun: "noun";
};
export declare type Scope = keyof typeof scopes;

index.ts

function strEnum<T extends string>(strings: Array<T>): {[K in T]: K} {
    return strings.reduce((res, key) => {
        res[key] = key;
        return res;
    }, Object.create(null));
}

export const scopes = strEnum([
    'noun:verb',
    'verb:adjective',
    'noun'
]);

export type Scope = keyof typeof scopes;

package.json

{
  "name": "declaration-output-mapped-types",
  "version": "1.0.0",
  "description": "Demonstrates bug with declaration output of mapped types",
  "main": "dist/index.js",
  "files": [
    "*.json",
    "*.md",
    "dist"
  ],
  "scripts": {
    "build": "tsc"
  },
  "keywords": ["typescript", "bug"],
  "author": "Garth Kidd <[email protected]>",
  "license": "ISC",
  "devDependencies": {
    "typescript": "^2.3.4"
  }
}

tsconfig.json

{
  "compilerOptions": {
    "declaration": true,
    "lib": [
      "es2015"
    ],
    "module": "commonjs",
    "moduleResolution": "node",
    "outDir": "dist",
    "sourceMap": false,
    "target": "es2015"
  },
  "include": [
    "*.ts"
  ]
}