Introduce fake light class for file of package

Fixes problems related to not working breakpoints (see comment at the top of
the class)

 #KT-3291 Fixed

compiler/jet.as.java.psi/src/org/jetbrains/jet/asJava/FakeLightClassForFileOfPackage.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2010-2013 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.jet.asJava;
+
+import com.intellij.psi.PsiClass;
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiFile;
+import com.intellij.psi.PsiManager;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.jet.lang.psi.JetFile;
+import org.jetbrains.jet.lang.resolve.java.JetJavaMirrorMarker;
+import org.jetbrains.jet.lang.resolve.name.FqName;
+
+/**
+ * This class serves as a workaround for usages of {@link JavaElementFinder#findClasses} which eventually only need names of files
+ * containing the class. When queried for a package class (e.g. test/TestPackage), {@code findClasses} along with a
+ * {@link KotlinLightClassForPackage} would also return multiple instances of this class for each file present in the package. The client
+ * code can make use of every file in the package then, since {@code getContainingFile} of these instances will represent the whole package.
+ * <p/>
+ * See {@link LineBreakpoint#findClassCandidatesInSourceContent} for the primary usage this was introduced
+ */
+/* package */ class FakeLightClassForFileOfPackage extends KotlinLightClassForPackageBase implements KotlinLightClass, JetJavaMirrorMarker {
+    private final KotlinLightClassForPackage delegate;
+    private final JetFile file;
+
+    public FakeLightClassForFileOfPackage(
+            @NotNull PsiManager manager, @NotNull KotlinLightClassForPackage delegate, @NotNull JetFile file
+    ) {
+        super(manager);
+        this.delegate = delegate;
+        this.file = file;
+    }
+
+    @Override
+    public PsiFile getContainingFile() {
+        return file;
+    }
+
+    @Override
+    public boolean isValid() {
+        // This is intentionally false to prevent using this as a real class
+        return false;
+    }
+
+
+    @NotNull
+    @Override
+    public FqName getFqName() {
+        return delegate.getFqName();
+    }
+
+    @NotNull
+    @Override
+    public PsiClass getDelegate() {
+        return delegate;
+    }
+
+    @NotNull
+    @Override
+    public PsiElement copy() {
+        return new FakeLightClassForFileOfPackage(getManager(), delegate, file);
+    }
+}

compiler/jet.as.java.psi/src/org/jetbrains/jet/asJava/JavaElementFinder.java

@@ -117,6 +117,13 @@ public class JavaElementFinder extends PsiElementFinder implements JavaPsiFacade
             KotlinLightClassForPackage lightClass = KotlinLightClassForPackage.create(psiManager, qualifiedName, filesForPackage);
             if (lightClass != null) {
                 answer.add(lightClass);
+
+                if (filesForPackage.size() > 1) {
+                    for (JetFile file : filesForPackage) {
+                        FakeLightClassForFileOfPackage fakeLightClass = new FakeLightClassForFileOfPackage(psiManager, lightClass, file);
+                        answer.add(fakeLightClass);
+                    }
+                }
             }
         }
     }