org.ekrich.config.ConfigResolver.scala Maven / Gradle / Ivy

package org.ekrich.config

/**
 * Implement this interface and provide an instance to
 * {@link ConfigResolveOptions#appendResolver ConfigResolveOptions.appendResolver()}
 * to provide custom behavior when unresolved substitutions are encountered
 * during resolution.
 *
 * @since 1.3.2
 */
trait ConfigResolver {

  /**
   * Returns the value to substitute for the given unresolved path. To get the
   * components of the path use
   * [[ConfigUtil$.splitPath ConfigUtil.splitPath(String)]].
   * If a non-null value is returned that value will be substituted, otherwise
   * resolution will continue to consider the substitution as still
   * unresolved.
   *
   * @param path the unresolved path
   * @return the value to use as a substitution or null
   */
  def lookup(path: String): ConfigValue

  /**
   * Returns a new resolver that falls back to the given resolver if this
   * one doesn't provide a substitution itself.
   *
   * It's important to handle the case where you already have the fallback
   * with a "return this", i.e. this method should not create a new object if
   * the fallback is the same one you already have. The same fallback may be
   * added repeatedly.
   *
   * @param fallback the previous includer for chaining
   * @return a new resolver
   */
  def withFallback(fallback: ConfigResolver): ConfigResolver
}