Gradle: how to run a task for specified input files? - gradle

Question

I have a Gradle build file which uses ProtoBuffer plugin and runs some tasks. At some point some tasks are run for some files, which are inputs to tasks.
I want to modify the set of files which is the input to those tasks. Say, I want the tasks to be run with files which are listed, one per line, in a particular file. How can I do that?
EDIT: Here is a part of rather big build.gradle which provides some context.
configure(protobufProjects) {
apply plugin: 'java'
ext {
protobufVersion = '3.9.1'
}
dependencies {
...
}
protobuf {
generatedFilesBaseDir = "$projectDir/gen"
protoc {
if (project.hasProperty('protocPath')) {
path = "$protocPath"
}
else {
artifact = "com.google.protobuf:protoc:$protobufVersion"
}
}
plugins {
...
}
generateProtoTasks {
all().each { task ->
...
}
}
sourceSets {
main {
java {
srcDirs 'gen/main/java'
}
}
}
}
clean {
delete protobuf.generatedFilesBaseDir
}
compileJava {
File generatedSourceDir = project.file("gen")
project.mkdir(generatedSourceDir)
options.annotationProcessorGeneratedSourcesDirectory = generatedSourceDir
}
}
The question is, how to modify the input file set for existing task (which already does something with them), not how to create a new task.
EDIT 2: According to How do I modify a list of files in a Gradle copy task? , it's a bad idea in general, as Gradle makes assumptions about inputs and outputs dependencies, which can be broken by this approach.

Answer 1

If you would have added the gradle file and more specific that would have been very helpful. I will try to give an example from what I have understood:
fun listFiles(fileName: String): List<String> {
val file = file(fileName).absoluteFile
val listOfFiles = mutableListOf<String>()
file.readLines().forEach {
listOfFiles.add(it)
}
return listOfFiles
}
tasks.register("readFiles") {
val inputFile: String by project
val listOfFiles = listFiles(inputFile)
listOfFiles.forEach {
val file = file(it).absoluteFile
file.readLines().forEach { println(it) }
}
}
Then run the gradle like this: gradle -PinputFile=<path_to_the_file_that_contains_list_of_files> readFiles