Add tapErrorZIO and tapErrorCauseZIO to Route and Routes

[tjarvstrand]

Useful for things like error logging or reporting to external services such as Sentry.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 10 lines in your changes are missing coverage. Please review.

Project coverage is 64.34%. Comparing base (709b459) to head (006b320).

Files	Patch %	Lines
...io-http/shared/src/main/scala/zio/http/Route.scala	0.00%	8 Missing ⚠️
...o-http/shared/src/main/scala/zio/http/Routes.scala	0.00%	2 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2755      +/-   ##
==========================================
- Coverage   64.42%   64.34%   -0.08%     
==========================================
  Files         148      148              
  Lines        8668     8678      +10     
  Branches     1589     1545      -44     
==========================================
  Hits         5584     5584              
- Misses       3084     3094      +10     

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[987Nabil]

iirc, ensures handled that the typed error is handled. But a cause (defect) might still happen. So I think there should be a tap on the handler here.

[tjarvstrand]

That doesn't seem to work as the Handled.handler's failure type is Response whereas f's failure type is Err which is not necessarily a Response.

[jdegoes]

You can catch the Cause[Err], and if it contains an Err, then you rethrow it. But if it's really a Cause[Nothing], i.e. pure defect, without an Err inside it, then you can allow that to be caught by f, since f can handle those (Cause[Nothing] is a subtype of Cause[Err]).

[jdegoes]

@tjarvstrand This does need to be fixed, and then will be good to merge!

[tjarvstrand]

Sorry, busy week! :/

I've been struggling a bit with the error case of f which, unless I'm mistaken, must be a Response. Does something like this make sense?

/**
   * Effectfully peeks at the unhandled failure cause of this Route.
   */
  final def tapErrorCauseZIO[Err1 >: Err](
    f: Cause[Err] => ZIO[Any, Err1, Any],
  )(implicit trace: Trace): Route[Env, Err1] =
    self match {
      case Provided(route, env)                        => Provided(route.tapErrorCauseZIO(f), env)
      case Augmented(route, aspect)                    => Augmented(route.tapErrorCauseZIO(f), aspect)
      case Handled(routePattern, handler, location)    =>
        Handled(
          routePattern,
          handler.tapErrorCauseZIO {
            case cause0: Cause[Err] => f(cause0).catchAllCause(cause => ZIO.fail(Response.fromCause(cause)))
            case _                  => ZIO.unit
          },
          location,
        )
      case Unhandled(rpm, handler, zippable, location) =>
        Unhandled(rpm, handler.tapErrorCauseZIO(f), zippable, location)
    }

[jdegoes]

When you get cause0, do errorOrCause, and if it's an error, you have to refail that, but if it's a Cause[Nothing], you can feed it to f.

[tjarvstrand]

Maybe I'm slow, but shouldn't handler.tapErrorCauseZIO leave the error channel of the original effect intact so that I don't have to refail it?

Not trying to be difficult. I just want to make sure I understand what's going on.

[jdegoes]

Ah yes, of course! Forgot the point of this function, which is tapping not recovering. 🤦‍♂️

[tjarvstrand]

👍

Tried to move too fast and now the build is failing. I'll have another look at this as soon as I can.

[tjarvstrand]

I'm afraid I think I'm in need of some assistance.

There are warnings in Scala 3 (which I have actually not used yet):

[warn] -- Unchecked Warning: /Users/tjarvstrand/src/zio-http/zio-http/shared/src/main/scala/zio/http/Route.scala:134:17
[warn] 134 |            case err: Fail[Err] => f(err.value).catchAllCause(cause => ZIO.fail(Response.fromCause(cause)))
[warn]     |                 ^
[warn]     |the type test for zio.Cause.Fail[Err] cannot be checked at runtime because its type arguments can't be determined from zio.Cause[zio.http.Response]

I'm assuming this is related to type erasure somehow, but I'm not sure why there's no warning in Scala 2. Any tips on how to proceed?