以设置为条件重新定义 sbt 任务 [英] Redefine an sbt task conditional on a setting
问题描述
我想重新定义一个以设置值为条件的 sbt 任务.在默认情况下,它应该执行原始任务,在其他情况下,我想运行一个自定义任务.
I would like to redefine an sbt task conditional on the value of a setting. In the default case, it should execute the original task, in the other case, I want to run a custom task.
给定任务和设置:
val someSetting = Def.settingKey[Boolean]("some setting")
val fooTask = Def.taskKey[String]("foo task")
someSetting := true
fooTask := {
println("** foo effect **")
"foo value"
}
尝试重新定义 fooTask:
Trying to redefine fooTask:
fooTask := {
if( someSetting.value ) fooTask
else Def.task("whatever")
}.value
给出编译错误:
build.sbt:39: error: Illegal dynamic dependency
if( someSetting.value ) fooTask
^
使用 Def.task
任务编译...
Using Def.task
the task compiles ...
fooTask := Def.task {
if( someSetting.value ) fooTask.value
else Def.task("whatever").value
}.value
...但是即使 someSetting
为 false 也会被执行!
... but gets executed even if someSetting
is false!
> set someSetting := false
[info] Defining *:someSetting
[info] The new value will be used by *:fooTask
[info] Reapplying settings...
> fooTask
** foo effect **
[success] Total time: 1 s, completed Mar 20, 2017 11:40:13 PM
尝试使用 Def.taskDyn
代替...
Trying to use Def.taskDyn
instead ...
fooTask := Def.taskDyn {
if( someSetting.value ) fooTask
else Def.task("whatever")
}.value
... 导致在运行时引用未定义的设置":
... results in "References to undefined settings at runtime":
> set someSetting := true
[info] Defining *:someSetting
[info] The new value will be used by *:fooTask
[info] Reapplying settings...
[info] Set current project to sbt-task-games (in build file:/Users/jast/playspace/untitled8/)
> fooTask
[trace] Stack trace suppressed: run last *:fooTask for the full output.
[error] (*:fooTask) sbt.Init$RuntimeUndefined: References to undefined settings at runtime.
[error] setting(ScopedKey(Scope(Select(ProjectRef(file:/Users/jast/playspace/untitled8/,untitled8)),Global,Global,Global),fooTask)) at RangePosition(/Users/jast/playspace/untitled8/build.sbt,LineRange(43,47)) referenced from ScopedKey(Scope(Select(ProjectRef(file:/Users/jast/playspace/untitled8/,untitled8)),Global,Global,Global),fooTask)
[error] Total time: 0 s, completed Mar 20, 2017 11:49:59 PM
推荐答案
在返回执行它的任务之前,您需要保存"对实际任务的引用.这就是 taskValue
的用途:
You need to "save" a reference to the actual task before returning a task that executes it. This is what taskValue
is for:
fooTask := Def.taskDyn {
val default = fooTask.taskValue
if (someSetting.value) Def.task(default.value)
else Def.task("whatever")
}.value
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