build.gradle

import java.util.regex.Pattern

/** Defines a custom task for updating version numbers. */
abstract class UpdateVersionTask extends DefaultTask {

    static final def VERSION_REGEX = "([0-9]+)\\.([0-9]+)\\.([0-9]+)(-SNAPSHOT)?"

    @Input
    String newVersion

    @InputFile
    File propertiesFile = project.file("${project.projectDir}/gradle.properties")

    @TaskAction
    def update() {
        if (newVersion == null) {
            throw new GradleException("Need to specify newVersion")
        }
        if (propertiesFile == null) {
            throw new GradleException("Need to specify gradlePropertiesFile")
        }
        if (!newVersion.matches(VERSION_REGEX)) {
            throw new GradleException("Invalid format for -PnewVersion. Expecting: ${VERSION_REGEX}")
        }
        def toSet = new Properties()
        propertiesFile.withInputStream { toSet.load(it) }
        toSet.version = newVersion
        propertiesFile.withOutputStream { toSet.store(it, "See LICENSE for license terms") }
    }
}

/** Updates the version to version specified with -PnewVersion=foo. */
task updateVersion(type: UpdateVersionTask) {
    newVersion = project.properties.newVersion
}

/** Updates the version to the next snapshot. */
task updateVersionToNextSnapshot(type: UpdateVersionTask) {
    def current = new Properties()
    propertiesFile.withInputStream { current.load(it) }
    def matcher = Pattern.compile(VERSION_REGEX).matcher(current.version)
    if (!matcher.find()) {
        throw new GradleException("Current version cannot be parsed: ${current.version} expected match of: ${VERSION_REGEX}")
    }
    def toSet = "${matcher.group(1)}.${matcher.group(2)}.${Integer.parseInt(matcher.group(3)) + 1}-SNAPSHOT"
    newVersion = toSet
}