TypeScript requires `dom` library even for `node` only projects.

Environment

Name	Version
msw	0.21.2
node	12.16.3
OS	macOS catalina 10.15.7 (19H2)

Problem

The msw TypeScript compilation requires dom library even for node only projects.

tsconfig.json

  {
    "compilerOptions": {
      "module": "commonjs",
      "target": "es6",
      "outDir": "out",
-     "lib": ["es6", "dom"],
+     "lib": ["es6"],
      "sourceMap": true,
      "strict": true,
    },
    "include": ["src/**/*"]
  }

Current behavior

When the dom library is missing, TS can’t resolve types like Request, URL, and ServiceWorker.

node_modules/msw/lib/types/utils/handlers/requestHandler.d.ts:9:82 - error TS2304: Cannot find name 'RequestInit'.

9     fetch: (input: string | MockedRequest<DefaultRequestBodyType>, requestInit?: RequestInit) => any;
                                                                                   ~~~~~~~~~~~

node_modules/msw/lib/types/utils/handlers/requestHandler.d.ts:13:10 - error TS2304: Cannot find name 'URL'.

13     url: URL;
            ~~~

node_modules/msw/lib/types/utils/handlers/requestHandler.d.ts:14:13 - error TS2304: Cannot find name 'Request'.

14     method: Request['method'];
               ~~~~~~~

Expected behavior

TypeScript should compile msw without dom library when used only for a node project.

Screenshots

Example project: https://gitlab.com/viktomas/showcase-msw-bug

[kettanaito]

@timdeschryver, I’ve tried that but that quickly leads to re-annotating half of the DOM. There are a ton of things missing ( fetch, XMLHttpRequest) or existing in a incompatible form (Event) between the DOM and NodeJS.

I’m thinking if we can output an entirely separate build for NodeJS that would derive from the same source, guaranteeing its integrity, but would have its own bundling and types. That way we could annotate the same utilities differently for NodeJS. That still doesn’t solve the issue that those utilities quite heavily rely on certain DOM types.

And I’ve completely forgot about the entry points. Even if we configure it the way described above the users won’t still see the difference, as they import utilities from msw and not msw/node. At this point I’m completely lost.

[kettanaito]

The dom lib is a dependency of msw. You should either add it to your project ("lib": ["dom"] in tsconfig.json) or use skipLibCheck altogether (not recommended). The library cannot assume in which environment it’s going to be used—that is runtime information. Thus, the library depends on the maximum possible scope of types, which includes dom.

I’m open to suggestions on how to annotate this better but I think there are no options currently available in TypeScript to have this support.