Using a gradle task generate a properties file to be included in a jar before the jar task is executed - gradle

Question

Before is a snippet of my build.gradle, it lists a series of tasks which should ideally be run in the following order:
createPropertiesFile
jar
obfuscate
deleteNonObfuscatedJar
deletePropertiesFile
I need createPropertiesFile to run before jar, as users are building the .jar using ./gradlew jar.
The problem I'm seeing at the moment is this error:
> Could not find method doFirst() for arguments [task ':createAuthenticationPropertiesFile']
on task ':jar' of type org.gradle.api.tasks.bundling.Jar.
I've also tried jar.dependsOn(project.tasks.createAuthenticationPropertiesFile) but I've seen that custom.properties is not included in the generated .jar when using jar.dependsOn
build.gradle:
nonObfuscatedJar = 'appNotObfuscated.jar'
task createPropertiesFile << {
def props = project.file('src/main/resources/custom.properties')
props << 'prop1=value1'
}
jar {
duplicatesStrategy = DuplicatesStrategy.EXCLUDE
archiveName = "$nonObfuscatedJar"
from sourceSets.main.output.classesDir
from configurations.compileOnly.asFileTree.files.collect { zipTree(it) }
include '**/*.class'
include '**/custom.properties'
manifest {
attributes 'Main-Class': 'com.bobbyrne01.App'
}
exclude 'META-INF/*.RSA', 'META-INF/*.SF','META-INF/*.DSA'
}
task obfuscate(type: proguard.gradle.ProGuardTask) {
configuration 'proguard.txt'
injars "$libsDir/$nonObfuscatedJar"
outjars "$libsDir/app.jar"
libraryjars "${System.getProperty('java.home')}/lib/rt.jar"
}
task deleteNonObfuscatedJar (type: Delete) {
delete "$libsDir/$nonObfuscatedJar"
}
task deletePropertiesFile (type: Delete) {
delete project.file('src/main/resources/custom.properties')
}
jar.doFirst(project.tasks.createPropertiesFile)
jar.finalizedBy(project.tasks.obfuscate)
jar.finalizedBy(project.tasks.deleteNonObfuscatedJar)
jar.finalizedBy(project.tasks.deletePropertiesFile)

Answer 1

As a workaround, move the properties file creation to the start of the jar task:
jar {
// Create properties file
def props = project.file('src/main/resources/custom.properties')
props << 'prop1=value1'
// Build jar
duplicatesStrategy = DuplicatesStrategy.EXCLUDE
archiveName = "$nonObfuscatedJar"
from sourceSets.main.output.classesDir
from configurations.compileOnly.asFileTree.files.collect { zipTree(it) }
include '**/*.class'
include '**/custom.properties'
manifest {
attributes 'Main-Class': 'com.bobbyrne01.App'
}
exclude 'META-INF/*.RSA', 'META-INF/*.SF','META-INF/*.DSA'
}