"external types" for d.ts files dependent on others #1402
Description
d.ts files on DefinitelyTyped frequently depend on other declaration files.
interface JSZipObject {
name: string;
dir: boolean;
date: Date;
comment: string;
options: JSZipObjectOptions;
asText(): string;
asBinary(): string;
asArrayBuffer(): ArrayBuffer;
asUint8Array(): Uint8Array;
//asNodeBuffer(): Buffer; <-- Disabled to prevent node.d.ts dependency
}Bigger d.ts files depend on multiple big d.ts files, which again depend on others. (Example: atom.d.ts, ...) Collecting all those required files may not only be painful but also be unnecessary, especially for those who just want to use a specific part of a d.ts file that is not dependent on anything.
A method to specify external types can help here, allowing users to exclude unwanted declaration files.
// jszip.d.ts
/// <reference path="../node/node.d.ts" />
external interface Buffer: "../node/node.d.ts";
// use.d.ts
/// <referernce path="jszip.d.ts" />
var zip: JSZipObject;
var text = zip.asText(); // works fine without node.d.ts
var buffer = zip.asNodeBuffer(); // typeof any when there is no node.d.ts;
// No error but a warning: "interface Buffer should be defined by "node.d.ts"interface Buffer { } may just work here, but not for classes as they are not open-ended.
// bar.d.ts
/// <reference path="foo.d.ts" />;
external class Foo: "foo.d.ts"; // This should not block Foo definition by foo.d.ts
interface Bar {
foo: Foo;
}