Macro implementation when using triggers is not working

[huntc]

This works:

discoveredDist <<= (dist in ReactiveRuntime)
  .storeAs(discoveredDist in Global)
  .triggeredBy(dist in ReactiveRuntime)

however this doesn't:

discoveredDist := (dist in ReactiveRuntime)
  .storeAs(discoveredDist in Global)
  .triggeredBy(dist in ReactiveRuntime)
  .value

[liff]

Minimal repro:

// build.sbt
val hello = taskKey[Unit]("hello")
val world = taskKey[Unit]("world")

hello := println("hello")
world := println("world")

world := (world triggeredBy hello).value // prints "hello", should print "hello\nworld"

// world <<= world triggeredBy hello // works

Run with sbt hello.

[cunei]

It seems this issue is only incidentally related to the macro expansion. The code that is generated when this expression is expanded:

world := (world triggeredBy hello).value

in the end happens to be similar to:

world <<= ((world triggeredBy hello) map ( a => a ))

In the latter expression, the triggeredBy for some reason gets ignored; that happens on 0.12.x as well. I'm doing some debugging now.

[eed3si9n]

old logic

If we consider a task to consists of two parts, value function and an attribute list, the existing behavior is defensible. <<= binds both the parts to the LHS task key whereas := creates a brand new task using the given value and a blank attribute list.

In that logic,

world := (world triggeredBy hello).value

is not much different from

world := {
  val x = (world triggeredBy hello).value
  123
}

or

world := 123

Functor law

The part that starts to break down is map.
The first functor law states that mapping with identity should not modify the original functor.
See also http://eed3si9n.com/herding-cats/Functor.html
It might not be strictly enforced, but the law matches the intuitive feel people on the standard collections too.

new ideas?

Even though it's forgetful, focusing only on the value using := is very valuable in flattening the learning curve of sbt.

One workaround might be to track triggers as a separate key:

onComplete in hello += world

This would move the trigger as if they are values, and at the end of the loading we can put them to the appropriate task attributes.

[gabro]

Is there a workaround to this issue that will achieve the same behavior without triggering a deprecation warning in sbt?

[cunei]

@dwijnand 👍

[jcranky]

This fix is not available on 0.13.x yet, right?

[dwijnand]

It's available in 0.13.14-RC1.

[jcranky]

thanks, worked fine with that version :)

[fdietze]

Hi, this does not seem to be fixed for me:

refreshBrowsers <<= refreshBrowsers.triggeredBy(WebKeys.assets in Assets)

works, while

refreshBrowsers := refreshBrowsers.triggeredBy(WebKeys.assets in Assets)

does not.

sbt.version=0.13.15

Project source: https://github.com/woost/wust2/blob/dff8fdcdd13d39dfaf51e61b9ec251b99d1e619c/build.sbt#L232

Do you need more information?

[jvican]

Did you miss '.value' intentionally in the code snippet that uses :=?

[fdietze]

Good catch! That was not intentional, it works with .value. Thank you!

It's strange though that I didn't get a compile error...

[eed3si9n]

It's because the expected Unit discards value, so it didn't catch the lack of .value invocation.

[mborra]

Hi to all, I have tried with :

compile in MultiJvm := ( compile in MultiJvm ).triggeredBy( compile in Test ).value

instead of:

compile in MultiJvm <<= ( compile in MultiJvm ) triggeredBy ( compile in Test )

But doesn't works

[jvican]

Which sbt version?

[mborra]

Sorry, 0.13.13

[jvican]

This thread says that the fix for triggeredBy is only available in 0.13.14. You need to update.

[mborra]

Sorry, you're right.

[cheevo]

// Here is a snippet that might help those that
// have had the same problem and need some example code showing a
// brief solution that works

sbt sbtVersion
[info] 1.0.2

Within build.sbt

lazy val copyDocAssetsTask = taskKey[Unit]("Copy doc assets")
target in Compile in doc := baseDirectory.value /"public/wiki"
copyDocAssetsTask := {
println("Copying doc Images")
val sourceDir = baseDirectory.value / "extra-resources"
val targetDir = (target in (Compile, doc)).value
val targ = targetDir / "/extra-resources"
println("From "+ sourceDir)
println("To "+ targ)
IO.copyDirectory(sourceDir, targ)
}
copyDocAssetsTask := (copyDocAssetsTask triggeredBy (doc in Compile)).value

call doc

sbt compile doc
[info] Main Scala API documentation successful.
Copying doc Images
From /root/fogcomput/code/Appliance/fogcomputlabs/extra-resources
To /root/fogcomput/code/Appliance/fogcomputlabs/public/wiki/extra-resources

Thanks to all on thread for doing the hard work.