Conditional logic in gradle build to only execute certain code when a specific task is running

Question

So, I am using a plugin in my gradle build (the plugin is org.flywaydb.flyway but that is not really relevant). I want to validate the caller has passed in a runtime parameter when tasks from this plugin are executing but not when other tasks are executing.

I pass options to the flyway plugin based on a supplied parameter. I want an error to be returned when a flywayTask is being executed and no parameter is supplied. When a non-flyway task is being run, I do not want to validate if the parameter is supplied.

gradle -PmyParam=myValue flywayMigration

=> should run code and there should be no error

gradle flywayMigration

=> should run code and should produce error (as no parameter supplied)

gradle jar

=> should not run code and no error should be produced

I have been reading about gradle configuration and execution which is fine but I still can't find a way to only run the code when the flyway plugin is bveing executed OR specific flyway tasks are being executed.

This is my current code:

if(gradle.taskGraph.hasTask("flywayMigrate")) {
    flyway {

        def dbCode, dbUser, dbPassword, dbUrl

        if (!project.hasProperty("db_env")) {
            throw new GradleException("Expected db_env property to be supplied for migration task. Can be passed" +
                    " at command line e.g. [gradle -Pdb_env=ex1 flywayMigrate]")

        } else {
            // do stuff

        }

        user = balh
        password = blah
        url = blah
        driver = 'oracle.jdbc.OracleDriver'
        cleanDisabled = true
        baselineOnMigrate = true
        baselineVersion = '1.0.0'

    }
}

To be clear, I only want this code:

if (!project.hasProperty("db_env")

to run for flyway tasks.

The code above throws this error:

Task information is not available, as this task execution graph has not been populated.

I've tried a few things here, any advice would be appreciated.

Answer 1

It's not really clear to me, what exactly do you want to do in case if this property is provided, but I think, you can do it without accesing task graph, just try to use doFirst Closure of the flywayMigrate task. Just something like this:

flywayMigrate.doFirst {
    if(!project.hasProperty("db_env")) {
        throw ...
    } else {
        //Do something
    }
}

And leave your plugin configuration free of any additional logic.

As for exception, have you tried to wait until graph is ready? It's usualy done as follows:

gradle.taskGraph.whenReady {taskGraph ->
    if(gradle.taskGraph.hasTask("flywayMigrate")) {
        ...
    }
}

Update: to answer the question from the comments

if I can attach doFirst to multiple tasks?

Yes, you can use somthing like:

//declare task names
def names = ["taskA", "taskB", "taskC"]
tasks.findAll {it ->
    //filter tasks with names       
    if (it.name in names)
        return it
}.each { it -> 
    //add some extra logic to it's doFirst closure
    it.doFirst {
        println 'hello'
    }
}

Just check, that all the tasks are exists before this configuration.