Rxjs: RxJS 6 requires "dom" lib when using TypeScript

[dwieeb]

RxJS version: 6.0.0-beta.4

Code to reproduce:

index.ts

import { Observable } from 'rxjs';

tsconfig.json

{
  "compilerOptions": {
    "target": "es6",
    "module": "commonjs",
    "moduleResolution": "node",
    "strict": true,
    "lib": [
      "es2015"
    ]
  },
  "files": [
    "index.ts"
  ]
}

Expected behavior: Successful compilation.

Actual behavior: Without "dom" in "lib", the following compilation error occurs:

❯ npx tsc --project tsconfig.json
node_modules/rxjs/internal/observable/fromEvent.d.ts(10,39): error TS2304: Cannot find name 'EventTarget'.
node_modules/rxjs/internal/observable/fromEvent.d.ts(10,103): error TS2304: Cannot find name 'NodeList'.
node_modules/rxjs/internal/observable/fromEvent.d.ts(10,114): error TS2304: Cannot find name 'HTMLCollection'.

[cartant]

This is down to having all of the factory functions - including fromEvent - now exported from within "rxjs/index.d.ts".

The distribution now relies upon a bundler to 'tree-shake' any unused exports. However, TypeScript will still see all of the exports - whether used or not. That means that when using RxJS v6 in a Node application, it's still necessary to include TypeScript's dom library.

This has the unfortunate effect of introducing a whole bunch of type and global declarations that are not appropriate for a Node target.

In v5, the dom TypeScipt lib would only have been required if fromEvent was used - because fromEvent supports Node and DOM event sources.

Maybe there's not too much that can be done about this - short of removing the dependency on the EventTarget, NodeList and HTMLCollection type declarations?

[dwieeb]

You could ship two sets of .d.ts files: browser and Node. This would offer a workaround for Node users using TypeScript's paths compiler option:

{
  "compilerOptions": {
    "baseUrl": ".",
    "target": "es6",
    "module": "commonjs",
    "moduleResolution": "node",
    "strict": true,
    "paths": {
      "rxjs": ["node_modules/rxjs/node/index.d.ts"]
    },
    "lib": [
      "es2015"
    ]
  },
  "files": [
    "index.ts"
  ]
}

[jasonaden]

You can also add the option skipLibCheck. Without this, you're re-typechecking d.ts files that were compiled during the rxjs build process. You don't need to re-typecheck these since they were type checked when produced.

This could be even more obvious if, for instance, a library you depend on had looser compilation flags than your project. Say the library had noImplicitAny: false and you set it to true. You wouldn't want a bunch of compilation errors since there's really nothing you can do about it.

Therefore you should typically be using skipLibCheck to ignore this type of warning.

[lock[bot]]

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