FilesScope should be smart enough to make a decision about searching in

libraries

java/java-tests/testSrc/com/intellij/find/FindManagerTest.java

@@ -306,7 +306,7 @@ public class FindManagerTest extends DaemonAnalyzerTestCase {
     findModel.setGlobal(true);
     findModel.setMultipleFiles(true);
     findModel.setCustomScope(true);
-    findModel.setCustomScope(new GlobalSearchScope.FilesScope(myProject, ContainerUtil.list(nonProjectFile)));
+    findModel.setCustomScope(GlobalSearchScope.filesScope(myProject, ContainerUtil.list(nonProjectFile)));
 
     assertSize(1, findUsages(findModel));
   }

platform/core-api/src/com/intellij/psi/search/GlobalSearchScope.java

@@ -310,11 +310,33 @@ public abstract class GlobalSearchScope extends SearchScope implements ProjectAw
     };
   }
 
+  
+  /**
+   * Please consider using this#filesWithLibrariesScope or this#filesWithoutLibrariesScope for optimization
+   */
   @NotNull
   public static GlobalSearchScope filesScope(@NotNull Project project, @NotNull Collection<VirtualFile> files) {
     return filesScope(project, files, null);
   }
 
+  /**
+   * Optimization. By default FilesScope makes a decision about searching in libraries by checking that
+   * at least one file is placed out of module roots. So if you're sure about files placement you can explicitly say FilesScope whether 
+   * it should include libraries or not in order to avoid checking each file. 
+   * Also, if you have a lot of files it might be faster to always search in libraries.
+   */
+  @NotNull
+  public static GlobalSearchScope filesWithoutLibrariesScope(@NotNull Project project, @NotNull Collection<VirtualFile> files) {
+    if (files.isEmpty()) return EMPTY_SCOPE;
+    return new FilesScope(project, files, false);
+  }
+  
+  @NotNull
+  public static GlobalSearchScope filesWithLibrariesScope(@NotNull Project project, @NotNull Collection<VirtualFile> files) {
+    if (files.isEmpty()) return EMPTY_SCOPE;
+    return new FilesScope(project, files, true);
+  }
+
   @NotNull
   public static GlobalSearchScope filesScope(@NotNull Project project, @NotNull Collection<VirtualFile> files, @Nullable final String displayName) {
     if (files.isEmpty()) return EMPTY_SCOPE;
@@ -721,11 +743,18 @@ public abstract class GlobalSearchScope extends SearchScope implements ProjectAw
   }
 
   public static class FilesScope extends GlobalSearchScope implements Iterable<VirtualFile> {
-    private final Collection<VirtualFile> myFiles; // files can be out of project roots
+    private final Collection<VirtualFile> myFiles;
+    private Boolean myHasFilesOutOfProjectRoots;
 
-    public FilesScope(final Project project, @NotNull Collection<VirtualFile> files) {
+    public FilesScope(@Nullable Project project, @NotNull Collection<VirtualFile> files) {
+      this(project, files, null);
+    }
+
+    // Optimization
+    private FilesScope(@Nullable  Project project, @NotNull Collection<VirtualFile> files, @Nullable Boolean hasFilesOutOfProjectRoots) {
       super(project);
       myFiles = files;
+      myHasFilesOutOfProjectRoots = hasFilesOutOfProjectRoots;
     }
 
     @Override
@@ -745,7 +774,7 @@ public abstract class GlobalSearchScope extends SearchScope implements ProjectAw
 
     @Override
     public boolean isSearchInLibraries() {
-      return false;
+      return hasFilesOutOfProjectRoots();
     }
 
     @Override
@@ -757,11 +786,28 @@ public abstract class GlobalSearchScope extends SearchScope implements ProjectAw
     public int hashCode() {
       return myFiles.hashCode();
     }
+    
+    private boolean hasFilesOutOfProjectRoots() {
+      if (myHasFilesOutOfProjectRoots == null) {
+        long i = System.currentTimeMillis();
+        myHasFilesOutOfProjectRoots = false;
+        Project project = getProject();
+        if (project != null && !project.isDefault()) {
+          for (VirtualFile file : myFiles) {
+            if (FileIndexFacade.getInstance(project).getModuleForFile(file) == null) {
+              myHasFilesOutOfProjectRoots = true;
+              break;
+            }
+          }
+        }
+      }
+      return myHasFilesOutOfProjectRoots;
+    }
 
     @Override
     public String toString() {
       List<VirtualFile> files = myFiles.size() <= 20 ? new ArrayList<VirtualFile>(myFiles) : new ArrayList<VirtualFile>(myFiles).subList(0,20);
-      return "Files: ("+ files +")";
+      return "Files: ("+ files +"); search in libraries: " + (myHasFilesOutOfProjectRoots != null ? myHasFilesOutOfProjectRoots : "unknown");
     }
 
     @Override

platform/lang-impl/src/com/intellij/psi/search/PredefinedSearchScopeProviderImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2014 JetBrains s.r.o.
+ * Copyright 2000-2015 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.
@@ -250,13 +250,7 @@ public class PredefinedSearchScopeProviderImpl extends PredefinedSearchScopeProv
         }
       });
       if (!selectedFiles.isEmpty()) {
-        return new DelegatingGlobalSearchScope(GlobalSearchScope.filesScope(project, selectedFiles)) {
-          @NotNull
-          @Override
-          public String getDisplayName() {
-            return "Selected Files";
-          }
-        };
+        return GlobalSearchScope.filesScope(project, selectedFiles, "Selected Files");
       }
     }
     return null;