Implement ZIO#debug and related methods #4818
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I think these should probably use the live console so you don't have to change your method signatures when you use them for debugging purposes. |
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Other question is whether we want it to be configurable regarding whether it prints and want to use a macro so we can eliminate the code if it isn't enabled. |
Oh yeah. That's a great idea. 😄 I'll do this.
I've seen some examples of this with Scala 3, but I'm not quite sure how to achieve it within the context of a library. Not sure where we'd put the |
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| * Taps the effect, printing the result of calling `.toString` on the value | ||
| */ | ||
| final def debug: ZIO[R, E, A] = | ||
| self.tapBoth( |
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I would how we should handle a defect here? It seems like it could be useful for debugging but the full cause can be extremely long. Maybe we could just show the first cause in that case?
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Something like?
/**
* Taps the effect, printing the result of calling `.toString` on the value
* or the error.
*/
final def debug: ZIO[R, E, A] =
self
.tapCause(cause =>
cause.find {
case Cause.Interrupt(fiberId) => s"<INTERRUPT> by $fiberId"
case Cause.Die(throwable) => s"<DIE> $throwable"
case Cause.Fail(error) => s"<FAIL> $error"
}.fold(UIO.unit) { message =>
UIO(println(message))
}
)
.tap(value => UIO(println(value)))
/**
* Taps the effect, printing the result of calling `.toString` on the value.
* Prefixes the output with the given message.
*/
final def debug(prefix: => String): ZIO[R, E, A] =
self
.tapCause(cause =>
cause.find {
case Cause.Interrupt(fiberId) => s"$prefix: <INTERRUPT> by $fiberId"
case Cause.Die(throwable) => s"$prefix: <DIE> $throwable"
case Cause.Fail(error) => s"$prefix: <FAIL> $error"
}.fold(UIO.unit) { message =>
UIO(println(message))
}
)
.tap(value => UIO(println(s"$prefix: $value")))There was a problem hiding this comment.
Also, I wouldn't mind not keeping it as it is, and letting the runtime render dies.
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Yes, I'm not sure either. We can always optimize that later. |
A useful method for debugging/teaching/learning.
putStrLnis a bit difficult to use in an ad hoc manner as it requires a string, so you have to write.tap(arg => console.putStrLn(a.toString)), which is a bit of a mouthful when you just want to peek at the current value.I've implemented
debuganddebug(prefix: String)and related methods for easily printing out the value. All it does istapandputStrLnafter callingtoString, also optionally prefixing the output with the specified message.This will output: