Host.delete() completes but never emits

[mina-skunk]

🐞 Bug report

Command (mark with an x)

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- [x] build
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- [ ] test
- [ ] e2e
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- [ ] add
- [ ] update
- [ ] lint
- [ ] xi18n
- [x] run
- [ ] config
- [ ] help
- [ ] version
- [ ] doc

Description

The observable returned by Host.delete() completes but never emits.

🔬 Minimal Reproduction

With the following builder and path being a dir that exists

export interface MyBuilderOptions {
  path: string;
}

export class MyBuilder implements Builder<MyBuilderOptions> {

  constructor(
    private context: BuilderContext
  ) { }

  public run({ options }: BuilderConfiguration<MyBuilderOptions>): Observable<BuildEvent> {
    return this.deleteIfExist(options.path).pipe(
      map(() => {
        return { success: true } as BuildEvent;
      })
    );
  }

  private deleteIfExist(path: string): Observable<void> {
    const fullPath = resolve(this.context.workspace.root, normalize(path));
    return this.context.host.exists(fullPath).pipe(
      tap(
        res => console.log(`exists:emit:${res}`), // true
        err => console.log(`exists:error:${err}`), // not hit
        () => console.log(`exists:complete`) // hit
      ),
      switchMap(exists => {
        console.log(`if (exists) => ${exists}`); // true
        if (exists) {
          return this.context.host.delete(fullPath).pipe(
            tap(
              res => console.log(`delete:emit:${res}`), // not hit
              err => console.log(`delete:error:${err}`), // not hit
              () => console.log(`delete:complete`) // hit
            )
          );
        }
        return of(null);
      }),
      tap(
        res => console.log(`return:emit:${res}`), // not hit
        err => console.log(`return:error:${err}`), // not hit
        () => console.log(`return:complete`) // hit
      )
    );
  }

}

the output is:

exists:emit:true
if (exists) => true
delete:complete
exists:complete
return:complete
Cannot read property 'success' of undefined
at RunCommand.runSingleTarget

notice that delete:emit and return:emit never hit

but if the dir dosn't exist

export class MyBuilder implements Builder<MyBuilderOptions> {
//...
  private deleteIfExist(path: string): Observable<void> {
    const fullPath = resolve(this.context.workspace.root, normalize(path));
    return this.context.host.exists(fullPath).pipe(
      tap(
        res => console.log(`exists:emit:${res}`), // false
        err => console.log(`exists:error:${err}`), // not hit
        () => console.log(`exists:complete`) // hit
      ),
      switchMap(exists => {
        console.log(`if (exists) => ${exists}`); // false
        if (exists) {
          return this.context.host.delete(fullPath).pipe(
            tap(
              res => console.log(`delete:emit:${res}`), // not hit
              err => console.log(`delete:error:${err}`), // not hit
              () => console.log(`delete:complete`) // not hit
            )
          );
        }
        return of(null);
      }),
      tap(
        res => console.log(`return:emit:${res}`), // null
        err => console.log(`return:error:${err}`), // not hit
        () => console.log(`return:complete`) // hit
      )
    );
  }
//...
}

the output is:

exists:emit:false
if (exists) => false
return:emit:null
exists:complete
return:complete

(with no error) notice that return:emit does hit

If the code path reaches Host.delete() the observable stream "short circuits" and completes immediately, causing the map(() => { return { success: true }; }) to never happen. Shouldn't it emit void then complete if successful.

🔥 Exception or Error

Cannot read property 'success' of undefined
TypeError: Cannot read property 'success' of undefined
at RunCommand.runSingleTarget (C:\Users\User\source\repos\autofluent-cloud\autofluent-clients\cli6\node_modules@angular\cli\models\architect-command.js:184:27)
at process._tickCallback (internal/process/next_tick.js:68:7)
at Function.Module.runMain (internal/modules/cjs/loader.js:744:11)
at startup (internal/bootstrap/node.js:285:19)
at bootstrapNodeJSCore (internal/bootstrap/node.js:739:3)

🌍 Your Environment

Angular CLI: 7.3.8
Node: 10.14.1
OS: win32 x64
Angular: 7.2.7
... animations, common, compiler, compiler-cli, core, forms
... http, language-service, platform-browser
... platform-browser-dynamic, router

Package                            Version
------------------------------------------------------------
@angular-devkit/architect          0.13.8
@angular-devkit/build-angular      0.13.8
@angular-devkit/build-ng-packagr   0.13.8
@angular-devkit/build-optimizer    0.13.8
@angular-devkit/build-webpack      0.13.8
@angular-devkit/core               7.3.8
@angular-devkit/schematics         7.3.8
@angular/cdk                       7.3.3
@angular/cli                       7.3.8
@angular/flex-layout               7.0.0-beta.23
@angular/material                  7.3.3
@ngtools/json-schema               1.1.0
@ngtools/webpack                   7.3.8
@schematics/angular                7.3.8
@schematics/update                 0.13.8
ng-packagr                         4.7.1
rxjs                               6.3.3
typescript                         3.2.4
webpack                            4.29.0

Anything else relevant?
The only workaround I found to work was

from(this.context.host.delete(fullPath).toPromise())

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