types: TextRequest class type is incorrect due to skipLibChecks: true

[ondreian]

The type definition here:

dash.js/index.d.ts

Lines 4107 to 4114 in 4b0b16d

	export class TextRequest extends FragmentRequest {
	constructor(url: string, type: string);
	url: string | null;
	type: 'InitializationSegment' | 'MediaSegment' | null;
	mediaType: MediaType;
	responseType: string;
	}

generates a type error when skipLibChecks: false is added to a containing project, because this type is incorrect.

Environment

• typescript: ^5.1.3
• Dash.js version: v4.7.0

Steps to reproduce

1. checkout isolated reproduce case here
2. cd dash-type-4.7.0
3. run yarn fail convenience script to reproduce the case with tsc

Console output

yarn build
yarn run v1.22.17
$ tsc && rimraf dist && webpack --config build/webpack.prod.js
index.d.ts:4110:9 - error TS2416: Property 'url' in type 'TextRequest' is not assignable to the same property in base type 'FragmentRequest'.
  Type 'string | null' is not assignable to type 'string'.
    Type 'null' is not assignable to type 'string'.

4110         url: string | null;
             ~~~


Found 1 error in index.d.ts:4110

This is because in Typescript, you cannot change the type of an already declared property like this. By default tsc init configures a project as "skipLibCheck": true

Which means that this silently fails as the types are never checked in the dash.js index.d.ts file during compile time.