Store: ofActionErrored

[torbonaut]

When observing errored Actions it would be useful to catch the error that made the action fail. Can the error be provided?

Versions

* ngxs: 3.0.1
* @angular/core: 6.0.3

Desired behavior

Error available within ofActionErrored

[IlCallo]

This would be a really good idea.
Use case: login which can fail for multiple reason, so there could be multiple throw statement inside a single action, each with a different message.
When listening to the Action stream it's necessary to understand _which_ error are we dealing with.

Ex.

    this.actions.pipe(
      ofActionErrored(Login)
    ).subscribe((action, error) => console.log(error));

[IlCallo]

I checked the code, it seems to me that this is actually just a matter of exposing the full ActionContext instead of mapping it to just the action, changing this

https://github.com/ngxs/store/blob/56660422c543f61aa7c0f3ee55e37f6bff8fc3b8/packages/store/src/operators/of-action.ts#L57

removing altogether mapAction.

Or, if you _really_ want to hide the status label, it's just a matter of changing the mapping there

https://github.com/ngxs/store/blob/56660422c543f61aa7c0f3ee55e37f6bff8fc3b8/packages/store/src/operators/of-action.ts#L69-L71

maybe like

function mapAction() {
  return map(({action, error}: ActionContext) => { action, error );
}

@markwhitfeld shall I make a PR?

[garthmason]

This would be very useful - any chance it'll make it in the next release?

[markwhitfeld]

@splincode Any chance you could have a look at how we could do this without introducing a breaking change?

[splincode]

@markwhitfeld I will try to see soon

[markwhitfeld]

This will be achievable using the ofActionCompleted pipe when v3.4 is released.
Use the @dev version now to try it out.
See this comment for the signature of what is returned by this pipe: https://github.com/ngxs/store/issues/710#issuecomment-447647487
This will be in the docs once PR #726 is merged

[IlCallo]

🎉🎉

Even though, the simplicity of returning the error via ofActionErrored would be the best.

If you consider this to be a breaking change, can we hope to see it in version 4.0 maybe?

[jtrancas]

I'm using the dev version (future 3.4) and I'm using a custom operator to mimic the ofActionErroed:

export const ofActionErroredWithError = (action: object) =>
  (source: Observable<ActionContext<typeof action>>) =>
    source.pipe(
      ofActionCompleted(action),
      filter((completion: ActionCompletion) => !!completion.result.error),
      map(completion => ({ action: completion.action, error: completion.result.error}))
    );

Unfortunately ofAction() does not expose the ActionContext instance, otherwise, it could be a solution for versions pre 3.4.