[gradle-user] Understanding the Life Cycle and <<

[Neil Chaudhuri]

So I pretty much ripped this off verbatim from the Gradle Cookbook:

task aggregateJavadoc(dependsOn: clean, type: Javadoc)   {
  source subprojects.collect { project ->
    project.sourceSets.main.allJava
  }
  destinationDir = file("${buildDir.absolutePath}/javadoc")
  classpath = files(subprojects.collect { project ->
    project.sourceSets.main.compileClasspath
  })
}

When I run this, everything works as expected.

But when I add << and run the following I get an error:

task aggregateJavadoc(dependsOn: clean, type: Javadoc)  <<  {
  source subprojects.collect { project ->
    project.sourceSets.main.allJava
  }
  destinationDir = file("${buildDir.absolutePath}/javadoc")
  classpath = files(subprojects.collect { project ->
    project.sourceSets.main.compileClasspath
  })
}

The error is

Execution failed for task ':aggregateJavadoc'.
Cause: Error validating task ':aggregateJavadoc': No value has been specified 
for property 'destinationDir'.

Again, the task is precisely written as the other but with the << added only.

I've read the docs pretty carefully on the lifecycle, and I am not able to 
figure out what the difference is between these two executions. I can see how 
something can fail in the configuration phase because not everything has been 
configured, but I have trouble understanding how anything can fail in the 
execution phase once everything is in place.

Any insight into the difference between these two tasks is appreciated.

Thanks.