Gradle - different task use different parameter - jenkins

Question

I have two tasks,task_1 should compress png files and task_2 should not compress png files,so i want to add an parameter to control it.
project.ext.set("compressPngs", 1);
task taskCompressPngs(type:Exec){
commandLine "myshell.sh"
args compressPngs
}
task task_1(dependsOn:'taskCompressPngs'){}
task task_2(dependsOn:'taskCompressPngs'){}
gradle.taskGraph.whenReady { taskGraph ->
if (taskGraph.hasTask(task_1))
{
compressPngs=1
}
if (taskGraph.hasTask(task_2))
{
compressPngs=0
}
}
But when i run task_1 or task_2，in task 'taskCompressPngs', 'compressPngs' passed to my script 'myshell.sh' always be 1, why? how to solve it?

Answer 1

taskCompressPngs gets configured before the configuration value is changed. Conditional configuration is rarely a good solution. A better approach is to declare two Exec tasks.

Answer 2

As others have mentioned, it's probably best to take the advice of #PeterNiederwieser and use two separate tasks, but if you really don't think you can, here are a couple other options that should work.
1) Check Gradle startParameter
Configure your reusable task based on which task is passed to gradle on the command line.
task taskCompressPngs(type: Exec) {
def compressPngs = 1
if(gradle.startParameter.taskNames.toString().toLowerCase().contains("task_2")) compressPngs = 0
commandLine "myshell.sh $compressPngs".tokenize()
}
This gives you a variable to use (gradle.startParameter.taskNames) that is available at configuration-time.
Here we change compressPngs to 0 only if task_2 is specified on the command line when running gradle.
I.E. gradlew task_1 will run myshell.sh 1, but gradlew task_2 (or even gradlew task_1 task_2) will run myshell.sh 0.
This logic could also be applied to a project property outside of the taskCompressPngs task - if, for example, you wanted to change other tasks too.
Again, this only works if "task_2" is specified in the command used to run gradle.
2) Use DefaultExecAction instead of Exec task
Instead of using a task of type Exec, you could write a custom task and check the taskGraph in it.
task taskCompressPngs << {
def compressPngs = 1
if(gradle.taskGraph.hasTask(two)) compressPngs = 2
org.gradle.process.internal.DefaultExecAction e = new org.gradle.process.internal.DefaultExecAction(getServices().get(org.gradle.api.internal.file.FileResolver.class))
e.commandLine("myshell.sh $compressPngs".tokenize())
e.execute()
}
This is just moves your existing logic from configuration-time to execution-time.
This requires the use of "internal" Gradle classes (which is bad), but it gives you a little more flexibility in how/when the shell command is run.
Note that these solutions were checked against Gradle 1.7 and Gradle 1.11.