In typescript 2.0, how to have a single declaration file for modules not available in the @types npm namespace (DefinitelyTyped repo)?

Question

In a typescript project I need to use the bytewise npm module. This package does not have a type definition in the DefinitelyTyped npm namespace, so I can't use the method described in typescript documentation:

npm install --save-dev @types/bytewise

Since there's no type declaration for this module, it is not possible to use it, as tsc complains with: error TS2307: Cannot find module 'bytewise'.

To fix the issue, I have written a declaration file for bytewise and added it to node_modules/@types/bytewise/index.d.ts, which worked perfectly.

However, this is a tedious common pattern: I use a small npm library for which there are no @types declaration, create a directory under node_modules/@types, add an index.d.ts containing the declarations for the library, then git force/add that file(since node_modules is ignored by default).

Clearly I don't plan to maintain those declarations forever under my private node_modules directory, eventually I'd like to contribute them back to DefinitelyTyped so they can be installed more easily later, but rather than creating a separate directory/file for each library I'm using, I'd rather have a single vendor.d.ts file in the root of my project with all declarations not available on npm. Something like this(this is what I have in my project ATM):

import bl = require("bl");
import {Stream} from "stream";

declare module "bytewise" {
  export function encode(val: any): bl;
  export function decode(val: bl): any;
  export const buffer: boolean;
  export const type: string;
}

declare module "JSONStream" {
  export function parse(patternOrPath?: string): Stream;
  export function stringify(open?: string, sep?: string, close?: string);
}

The question is: How do I make these declarations available to all files in my project? I have tried modifying tsconfig.json to include it before the entry point:

{
  "compilerOptions": {
    "target": "es6",
    "module": "commonjs",
    "noImplicitAny": false,
    "removeComments": true,
    "preserveConstEnums": true,
    "outDir": "out",
    "sourceMap": true
  },
  "files": [
    "vendor.d.ts",
    "index.ts"    
  ]
}

but still get error TS2307: Cannot find module 'bytewise'. in the files where I have import * as bytewise from "bytewise";. I also tried adding a /// <reference path="..." /> comment pointing to vendor.d.ts but got the same error. Do I really need to have a separate declaration file for each npm module or am I missing something?

Ed Staub Ed Staub · Accepted Answer · 2017-08-15T16:08:26

Just include vendor.d.ts in your project, with no special configuration, but with one key change: move the two imports at the top to just after the line

declare module "bytewise" {

Any exports or imports outside of declarations will make this fail, with cryptic messages like:

Error:(3, 16) TS2665:Invalid module name in augmentation. Module 'bytewise' resolves to an untyped module at 'my-project/node_modules/bytewise/bytewise.js'.

In typescript 2.0, how to have a single declaration file for modules not available in the @types npm namespace (DefinitelyTyped repo)?

1 Answers