TypeScript require with type checking

Question

I am using TypeScript v1.4.1 and would like to require an external module (in this case "chai") and have it be type checked.

However, I am running into some sort of naming conflict with this code:

/// <reference path="../typings/node/node.d.ts" />
/// <reference path="../typings/chai/chai.d.ts" />
/// <reference path="../typings/mocha/mocha.d.ts" />

var chai = require("chai");

var expect = chai.expect;
var assert = chai.assert;

describe("TEST", () =>
{
   it("true should be true", (done)=>
   {
      expect(true).to.be.true;
      done();
   });
});

With this definition file:

declare module chai {
   ...
}
declare module "chai" {
   export = chai;
}

Compiling gives these errors:

test/test.ts(5,5): error TS2300: Duplicate identifier 'chai'.
typings/chai/chai.d.ts(6,16): error TS2300: Duplicate identifier 'chai'.

It seems my only option is rename my chai variable name in test.ts. That seems clunky AND won't type check the use of the renamed chai variable.

Any advice?

Answer 1

Use the import keyword with require instead of var

import chai = require('chai');

And compile with --module commonjs if you're not already

Or, if for some reason you don't want the test code to be an external module, adding a type annotation will preserve type checking.

var c: typeof chai = require("chai");

Answer 2

Since TypeScript 3.9 Beta was released it's possible to use require with typing

Example:

const {someValue} = require('fs')

"TypeScript now automatically detects the types of imports you're using to keep your file's style clean and consistent."

ref.https://devblogs.microsoft.com/typescript/announcing-typescript-3-9-beta/