Remove private properties/methods from publicApi interfaces

🐞 bug report

Affected Package

All @angular packages are affected

Is this a regression?

I am not sure, possibly at some point.

Description

If an angular class has any private properites/methods we cannot use it, but this will prevent us creating mock of that class for testing.

🔬 Minimal Reproduction

export declare class QueryList<T> {
    readonly dirty = true; // <-- Also an error, this should be boolean
    private _results;
    readonly changes: Observable<any>;
    readonly length: number;
    readonly first: T;
    readonly last: T;
    // ...
}

export QueryListMock<T> implements QueryList<T> {
    readonly dirty = true as true;
    private _results;
    readonly changes: Observable<any>;
    readonly length: number;
    readonly first: T;
    readonly last: T;
    // ...
}

As this is typescript relate issue I have typescript playground: here

🔥 Exception or Error

Class 'QueryListMock<T>' incorrectly implements class 'QueryList<T>'. Did you mean to extend 'QueryList<T>' and inherit its members as a subclass?
  Types have separate declarations of a private property '_results'.

🌍 Your Environment

Angular Version:

Angular CLI: 7.1.2
Node: 9.11.1
OS: win32 x64
Angular: 7.2.4
... animations, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.11.2
@angular-devkit/build-angular     0.11.2
@angular-devkit/build-optimizer   0.11.2
@angular-devkit/build-webpack     0.11.2
@angular-devkit/core              7.1.2
@angular-devkit/schematics        7.1.2
@angular/cli                      7.1.2
@ngtools/webpack                  7.1.2
@schematics/angular               7.1.2
@schematics/update                0.11.2
rxjs                              6.4.0
typescript                        3.2.4
webpack                           4.23.1

Anything else relevant? This is due to https://github.com/Microsoft/TypeScript/issues/18499, as it seems, they wont resolve that anytime soon.

[pkozlowski-opensource]

TypeScript aside we should be really exposing QueryList as an interface to users (without any private properties). Today we leak implementation details of the QueryList to our users 😦

[Akxe]

@dawidgarus that is a very good point, TS should solve this not Angular I guess. Then there is that think that QueryList has property dirty with type true, not boolean… It propably should be fixed