Use delegation instead of inheritance

core/src/main/scala/sbt/librarymanagement/LibraryManagement.scala

@@ -6,12 +6,21 @@ import sbt.io.Hash
 import sbt.librarymanagement.syntax._
 
 /**
- * Helper mixin to provide methods for library management
+ * Library management API to resolve dependencies.
  */
-abstract class LibraryManagement extends LibraryManagementInterface {
+class LibraryManagement private[sbt] (lmEngine: LibraryManagementInterface) {
   import sbt.internal.librarymanagement.InternalDefaults._
   import sbt.internal.librarymanagement.UpdateClassifiersUtil._
 
+  /**
+   * Builds a ModuleDescriptor that describes a subproject with dependencies.
+   *
+   * @param moduleSetting It contains the information about the module including the dependencies.
+   * @return A `ModuleDescriptor` describing a subproject and its dependencies.
+   */
+  def moduleDescriptor(moduleSetting: ModuleDescriptorConfiguration): ModuleDescriptor =
+    lmEngine.moduleDescriptor(moduleSetting)
+
   /**
    * Build a ModuleDescriptor that describes a subproject with dependencies.
    *
@@ -30,6 +39,22 @@ abstract class LibraryManagement extends LibraryManagementInterface {
     moduleDescriptor(moduleSetting)
   }
 
+  /**
+   * Resolves the given module's dependencies performing a retrieval.
+   *
+   * @param module The module to be resolved.
+   * @param configuration The update configuration.
+   * @param uwconfig The configuration to handle unresolved warnings.
+   * @param log The logger.
+   * @return The result, either an unresolved warning or an update report. Note that this
+   *         update report will or will not be successful depending on the `missingOk` option.
+   */
+  def update(module: ModuleDescriptor,
+             configuration: UpdateConfiguration,
+             uwconfig: UnresolvedWarningConfiguration,
+             log: Logger): Either[UnresolvedWarning, UpdateReport] =
+    lmEngine.update(module, configuration, uwconfig, log)
+
   /**
    * Returns a `ModuleDescriptor` that depends on `dependencyId`.
    *
@@ -192,7 +217,7 @@ abstract class LibraryManagement extends LibraryManagementInterface {
     }).mkString(", ")
 }
 
-/**
- * Helper mixin to provide methods for publisher
- */
-abstract class Publisher extends PublisherInterface
+object LibraryManagement {
+  def apply(lmEngine: LibraryManagementInterface): LibraryManagement =
+    new LibraryManagement(lmEngine)
+}

core/src/main/scala/sbt/librarymanagement/LibraryManagementInterface.scala

@@ -4,7 +4,7 @@ import java.io.File
 import sbt.util.Logger
 
 /**
- * Interface for library management
+ * Interface for library management intended for library management engine authors.
  */
 abstract class LibraryManagementInterface {
 

core/src/main/scala/sbt/librarymanagement/Publisher.scala

@@ -0,0 +1,47 @@
+package sbt.librarymanagement
+
+import java.io.File
+import sbt.util.Logger
+
+/**
+ * Library management API to publish artifacts.
+ */
+class Publisher private[sbt] (publisherEngine: PublisherInterface) {
+
+  /**
+   * Builds a ModuleDescriptor that describes a subproject with dependencies.
+   *
+   * @param moduleSetting It contains the information about the module including the dependencies.
+   * @return A `ModuleDescriptor` describing a subproject and its dependencies.
+   */
+  def moduleDescriptor(moduleSetting: ModuleDescriptorConfiguration): ModuleDescriptor =
+    publisherEngine.moduleDescriptor(moduleSetting)
+
+  /**
+   * Publishes the given module.
+   *
+   * @param module The module to be published.
+   * @param configuration The publish configuration.
+   * @param log The logger.
+   */
+  def publish(module: ModuleDescriptor, configuration: PublishConfiguration, log: Logger): Unit =
+    publisherEngine.publish(module, configuration, log)
+
+  /**
+   * Makes the `pom.xml` file for the given module.
+   *
+   * @param module The module for which a `.pom` file is to be created.
+   * @param configuration The makePomFile configuration.
+   * @param log The logger.
+   * @return The `File` containing the POM descriptor.
+   */
+  def makePomFile(module: ModuleDescriptor,
+                  configuration: MakePomConfiguration,
+                  log: Logger): File =
+    publisherEngine.makePomFile(module, configuration, log)
+}
+
+object Publisher {
+  def apply(publisherEngine: PublisherInterface): Publisher =
+    new Publisher(publisherEngine)
+}

ivy/src/main/scala/sbt/librarymanagement/ivy/IvyLibraryManagement.scala

@@ -5,7 +5,7 @@ package ivy
 import sbt.internal.librarymanagement._
 import sbt.util.Logger
 
-class IvyLibraryManagement private[sbt] (val ivySbt: IvySbt) extends LibraryManagement {
+class IvyLibraryManagement private[sbt] (val ivySbt: IvySbt) extends LibraryManagementInterface {
   type Module = ivySbt.Module
 
   override def moduleDescriptor(moduleSetting: ModuleDescriptorConfiguration): ModuleDescriptor = {
@@ -26,5 +26,5 @@ class IvyLibraryManagement private[sbt] (val ivySbt: IvySbt) extends LibraryMana
 
 object IvyLibraryManagement {
   def apply(ivyConfiguration: IvyConfiguration): LibraryManagement =
-    new IvyLibraryManagement(new IvySbt(ivyConfiguration))
+    LibraryManagement(new IvyLibraryManagement(new IvySbt(ivyConfiguration)))
 }

ivy/src/main/scala/sbt/librarymanagement/ivy/IvyPublisher.scala

@@ -6,7 +6,7 @@ import sbt.internal.librarymanagement._
 import sbt.util.Logger
 import java.io.File
 
-class IvyPublisher private[sbt] (val ivySbt: IvySbt) extends Publisher {
+class IvyPublisher private[sbt] (val ivySbt: IvySbt) extends PublisherInterface {
   type Module = ivySbt.Module
 
   override def moduleDescriptor(moduleSetting: ModuleDescriptorConfiguration): ModuleDescriptor = {
@@ -31,5 +31,5 @@ class IvyPublisher private[sbt] (val ivySbt: IvySbt) extends Publisher {
 
 object IvyPublisher {
   def apply(ivyConfiguration: IvyConfiguration): Publisher =
-    new IvyPublisher(new IvySbt(ivyConfiguration))
+    Publisher(new IvyPublisher(new IvySbt(ivyConfiguration)))
 }