Gradle run task only on defined property

Question

I am struggling to let a task only execute when a specific value is defined.

I'm using Gradle 3.5.

task signJar(type: SignJar, dependsOn: reobfJar) {
    onlyIf {
        project.hasProperty('mod_keystore')
    }

    keyStore = project.keyStore
    alias = project.keyStoreAlias
    storePass = project.keyStorePass
    keyPass = project.keyStoreKeyPass
    inputFile = jar.archivePath
    outputFile = jar.archivePath
}

As you can see, I already tried the onlyIf statement, but the task still runs. This results into a crash:

Could not get unknown property 'keyStore' for root project 'JustAnotherEnergy' of type org.gradle.api.Project.

The property 'mod_keystore' is no where defined, but the code get's executed.

task signJar(type: SignJar, dependsOn: reobfJar) {
    if(project.hasProperty('mod_keystore')) {
        keyStore = project.keyStore
        alias = project.keyStoreAlias
        storePass = project.keyStorePass
        keyPass = project.keyStoreKeyPass
        inputFile = jar.archivePath
        outputFile = jar.archivePath
    }
}

This works. The code does not get executed, but I'm running into other problems: If the property 'mod_keystore' is not defined, Gradle can't set a value for the for example 'keyStore' property, but the task SignJar requires this values to be set.

This means this task should only be executed when the property 'mod_keystore' is defined. If it is not defined, the task should be skipped.

Answer 1

As you can see, I already tried the onlyIf statement, but the task still runs.

No, the task does not run. You need to distinguish between the configuration phase and the execution phase. The task closure, where you are setting your task properties, is executed during the configuration phase, right after the task is created. Only task actions (defined by the task type) and closures added via doFirst or doLast are executed during the execution phase.

If you disable or skip a task via onlyIf or enabled, you only disable / skip the execution (phase) of the task, not its configuration (phase).

As a solution for your specific problem, you can rely on your first approach with the onlyIf condition, but add a fail-safe way to access your project properties:

task signJar(type: SignJar, dependsOn: reobfJar) {
    onlyIf {
        hasProperty('mod_keystore')
    }

    keyStore = findProperty('keyStore')
    alias = findProperty('keyStoreAlias')
    storePass = findProperty('keyStorePass')
    keyPass = findProperty('keyStoreKeyPass')
    inputFile = jar.archivePath
    outputFile = jar.archivePath
}