Add class QuickAssistMapping

A mapping class for Eclipse configuration that provides a better API.

org.scala-ide.sdt.core/src/org/scalaide/core/internal/quickassist/QuickAssistMapping.scala

@@ -0,0 +1,41 @@
+package org.scalaide.core.internal.quickassist
+
+import org.scalaide.core.quickassist.QuickAssist
+import org.scalaide.util.eclipse.EclipseUtils
+
+object QuickAssistMapping {
+
+  final val QuickAssistId = "org.scala-ide.sdt.core.quickAssists"
+
+  /**
+   * Returns all existing quick assists mapped to the [[QuickAssistMapping]]
+   * class. If an error occurred while trying to retrieve information for a
+   * quick assist, it is filtered out and the error is logged.
+   */
+  def mappings: Seq[QuickAssistMapping] = {
+    val elems = EclipseUtils.configElementsForExtension(QuickAssistId)
+    elems flatMap { e =>
+      EclipseUtils.withSafeRunner(s"Error occurred while trying to retrieve information from extension '$QuickAssistId'") {
+        QuickAssistMapping(e.getAttribute("id"))(e.createExecutableExtension("class").asInstanceOf[QuickAssist])
+      }
+    }
+  }
+}
+
+/**
+ * A mapping for a quick assist extension that allows easy access to the defined
+ * configuration. For documentation of the defined fields, see the quick assist
+ * extension point.
+ */
+case class QuickAssistMapping(id: String)(unsafeInstanceAccess: QuickAssist) {
+
+  /**
+   * Gives access to the actual quick assist instance. Because these instances
+   * can be defined by third party plugins they need to be executed in a safe
+   * mode to protect the IDE against corruption.
+   *
+   * If an error occurs in `f` `None` is returned, otherwise the result of `f`.
+   */
+  def withInstance[A](f: QuickAssist => A): Option[A] =
+    EclipseUtils.withSafeRunner(s"Error occurred while executing quick assist '$id'")(f(unsafeInstanceAccess))
+}