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

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.