Gradle Goodness: Replacing Operator for Tasks
This operator confuses a lot people who are new to Gradle because without the operator, we are configuring a task instead of adding actions.
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Join For FreeGradle 3.2 deprecates the <<
operator to add actions to a task. The <<
operator maps to the leftShift
method of a task. This operator confuses a lot people who are new to Gradle because without the operator, we are configuring a task instead of adding actions. I can say from experience that the mistake is easily made. If we use the <<
in our build script with Gradle 3.2, we get a warning on the console. The warning message already mentions a solution: use the doLast
method to add actions.
In the following example build script, we define the task deprecatedSample
using the <<
operator. The other task newSample
uses the doLast
method to add an action:
// Since Gradle 3.2 the << (leftShift) operator
// is deprecated. The operator can confuse
// people, because without the operator
// we would configure the deprecatedSample task,
// instead of adding the action statement:
// println 'Sample task'.
task deprecatedSample << {
println 'Sample task'
}
// To have no confusion we should use
// the doLast method of a task to add
// the action statement:
// println 'Sample task'.
task newSample {
doLast {
println 'Sample task'
}
}
When we run the deprecatedSample
task, we see in the output the warning that the leftShift
method has been deprecated:
$ gradle deprecatedSample
The Task.leftShift(Closure) method has been deprecated and is scheduled to be removed in Gradle 5.0. Please use Task.doLast(Action) instead.
at build_dq65b0mbv52w2ikhya3h9ru8d.run(/Users/mrhaki/Projects/mrhaki.com/blog/posts/samples/gradle/leftShift/build.gradle:7)
:deprecatedSample
Sample task
BUILD SUCCESSFUL
Total time: 0.793 secs
$
We still have time to fix our build scripts, because in Gradle 5 the leftShift
method will be removed.
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