mobx 6.7.0 leaks @types/node global typings

[kris7t]

Intended outcome: When using mobx in a TypeScript in a frontend-only project, it should be possible to use the DOM typings for globals such as setTimeout (which should return a number).

Actual outcome: The globals get their typings from @types/node, because mobx/dist/api/when.d.ts contains a spurious

/// <reference types="node" />

since 223e368. Unfortunately, global typings referenced by imported files are automatically propagated to importing packages: microsoft/TypeScript#22331 (comment)

In particular, setTimeout now return NodeJS.Timeout even if "node" is omitted from compilerOptions.types in tsconfig.json. Globals not present in DOM, such as process, are also visible, which is particularly dangerous for type safety.

How to reproduce the issue:

Create a TypeScript project with a tsconfig.json containing

{
    "compilerOptions": {
        "libs": []
    }
}

Observe that if mobx 6.6.2 is imported in the project, globals like setTimeout have their types as specified in DOM (e.g., setTimeout returns number): https://codesandbox.io/s/currying-worker-yj8gt6?file=/index.tsx

If mobx 6.7.0 is imported, the globals have their types as in @types/node, because mobx references the node global typings: https://codesandbox.io/s/sleepy-bird-dh354u?file=/index.tsx

Versions

• typescript 4.9.3
• mobx 6.7.0

[urugator]

Thank you for the report.
PR #3583.
Let me know if there is a better solution.