Added handy add/addAll/getList methods for list keys in CompilerConfiguration.

compiler/frontend/src/org/jetbrains/jet/config/CompilerConfiguration.java

@@ -21,6 +21,11 @@ import com.intellij.openapi.util.UserDataHolderBase;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+
 /**
  * @author Evgeny Gerashchenko
  * @since 7/3/12
@@ -28,11 +33,33 @@ import org.jetbrains.annotations.Nullable;
 public class CompilerConfiguration {
     private final UserDataHolderBase holder = new UserDataHolderBase();
 
+    @Nullable
     public <T> T get(@NotNull Key<T> key) {
         return holder.getUserData(key);
     }
 
+    @NotNull
+    public <T> List<T> getList(@NotNull Key<List<T>> key) {
+        List<T> data = holder.getUserData(key);
+        if (data == null) {
+            return Collections.emptyList();
+        }
+        else {
+            return Collections.unmodifiableList(data);
+        }
+    }
+
     public <T> void put(@NotNull Key<T> key, @Nullable T value) {
         holder.putUserData(key, value);
     }
+
+    public <T> void add(@NotNull Key<List<T>> key, @NotNull T value) {
+        List<T> list = holder.putUserDataIfAbsent(key, new CopyOnWriteArrayList<T>());
+        list.add(value);
+    }
+
+    public <T> void addAll(@NotNull Key<List<T>> key, @NotNull Collection<T> value) {
+        List<T> list = holder.putUserDataIfAbsent(key, new CopyOnWriteArrayList<T>());
+        list.addAll(value);
+    }
 }