Appendix A
Potential Traps
A.1 Groovy Script Variables
For Gradle users it is important to understand how Groovy deals with script variables. Groovy has to type of script
variables. One with a local scope and one with a script wide scope.
String localScope1 = 'localScope1'
def localScope2 = 'localScope2'
scriptScope = 'scriptScope'
println localScope1
println localScope2
println scriptScope
closure = {
println localScope1
println localScope2
println scriptScope
}
def method() {
try {localScope1} catch(MissingPropertyException e) {println 'localScope1NotAvailable' }
try {localScope2} catch(MissingPropertyException e) {println 'localScope2NotAvailable' }
println scriptScope
}
closure.call()
method()
>groovy scope.groovy
localScope1
localScope2
scriptScope
localScope1
localScope2
scriptScope
localScope1NotAvailable
localScope2NotAvailable
scriptScope
Variables which are declared with a type modifier are visible within closures but not visible within methods. This is a heavily discussed behavior
in the Groovy community.
A.2 Configuration and Execution Phase
It is important to keep in mind that Gradle has a distinct configuration and execution phase (see chapter 13).
classesDir = new File('build/classes')
classesDir.mkdirs()
createTask('clean') {
ant.delete(dir: 'build')
}
createTask('compile', dependsOn: 'clean') {
if (!classesDir.isDirectory()) {
println 'The class directory does not exists. I can not operate'
// do something
}
// do something
}
>gradle -q -bmkdirTrap.gradle compile
The class directory does not exists. I can not operate
As the creation of the directory happens during the configuration phase, the clean task removes the directory during the
execution phase.