SbtAddHook.scala

import sbt.*

/** Creates [[Def.Setting]] from [[SettingKey]] manipulating with [[State]], by assigning an action
  * that will perform previous action assigned to this key, and then evaluate parameter `hook`,
  * which may access and modify setting's state.
  *
  * @example
  * {{{
  *   lazy val someProject = (project in file("some"))
  *     .settings(
  *       addHook(Global / onLoad) { s =>
  *         println(s"Loaded! Current state: $s")
  *         s
  *       }
  *     )
  * }}}
  */
def addHook(settingKey: SettingKey[State => State])(hook: State => State) =
  settingKey := settingKey.value.andThen(hook)

/** Version of [[addHook]] for `hooks` that only perform side effect.
  *
  * @example
  * {{{
  *   lazy val someProject = (project in file("some"))
  *     .settings(
  *       addIdempotentHook(Global / onLoad) {
  *         println("Loaded! No access to the state.")
  *       }
  *     )
  * }}}
  */
def addIdempotentHook(settingKey: SettingKey[State => State])(hook: => Unit) =
  addHook(settingKey)(s => { hook; s })