Gradle task that runs ktlint only over changed files

ktlint.gradle

configurations { ktlint }
dependencies { ktlint "com.pinterest:ktlint:$ktlintVersion" }

task ktlintCi(type: JavaExec, group: "verification") {
  description = "Run Kotlin linter on changed files."
  group = "CI"
  main = "com.pinterest.ktlint.Main"
  classpath = configurations.ktlint

  doFirst {
    def changedFilesList = getDiffedFilesFromBranch("main")

    def ignoredFiles = "!**/src/**/*Test.kt"
    if (changedFilesList.isEmpty()) {
      println("No kotlin files changed! Ignoring all files...")
      ignoredFiles = "!**/src/**"
    } else {
      println("Running ktlint on the changed files:")
      changedFilesList.each { println(it) }
    }

    def reportDir = "$buildDir/reports/ktlint"
    def params = [
      *changedFilesList,
      ignoredFiles,
      "--format",
      "--relative",
      "--reporter=checkstyle,output=$reportDir/ktlint-checkstyle.xml",
      "--reporter=html,output=$reportDir/report.html"
    ]
    args(params)
  }
}

private static List<String> getDiffedFilesFromBranch(String branch) {
  def cmd = "git diff --diff-filter=d --name-only origin/$branch --relative | grep '\\.kt\\?\$'"
  def outputStream = new ByteArrayOutputStream()
  ['sh', '-c', cmd].execute().waitForProcessOutput(outputStream, System.err)

  return mapOutputToStringList(outputStream)
}

//get double quoted, comma separated list of files
private static List<GString> mapOutputToStringList(ByteArrayOutputStream outputStream) {
  if (outputStream.toString().isEmpty()) return []
  return outputStream.toString()
    .split("\\.kt\n")
    .collect { "${it}.kt" }
}

@iurysza which classpath do you use?