diff --git a/platform/indexing-impl/src/com/intellij/psi/impl/cache/impl/id/IdIndex.java b/platform/indexing-impl/src/com/intellij/psi/impl/cache/impl/id/IdIndex.java
index ad76a809da90..9929c1c586d2 100644
--- a/platform/indexing-impl/src/com/intellij/psi/impl/cache/impl/id/IdIndex.java
+++ b/platform/indexing-impl/src/com/intellij/psi/impl/cache/impl/id/IdIndex.java
@@ -91,7 +91,7 @@ public class IdIndex extends FileBasedIndexExtension<IdIndexEntry, Integer> {
 
   @Override
   public int getVersion() {
-    return 11 + (ourSnapshotMappingsEnabled ? 0xFF:0); // TODO: version should enumerate all word scanner versions and build version upon that set
+    return 12 + (ourSnapshotMappingsEnabled ? 0xFF:0); // TODO: version should enumerate all word scanner versions and build version upon that set
   }
 
   @Override
diff --git a/platform/lang-impl/src/com/intellij/find/ngrams/TrigramIndex.java b/platform/lang-impl/src/com/intellij/find/ngrams/TrigramIndex.java
index 72f5f947d0e7..9025357b4908 100644
--- a/platform/lang-impl/src/com/intellij/find/ngrams/TrigramIndex.java
+++ b/platform/lang-impl/src/com/intellij/find/ngrams/TrigramIndex.java
@@ -103,7 +103,7 @@ public class TrigramIndex extends ScalarIndexExtension<Integer> implements Custo
 
   @Override
   public int getVersion() {
-    return ENABLED ? 2 + (IdIndex.ourSnapshotMappingsEnabled ? 0xFF:0) : 1;
+    return ENABLED ? 3 + (IdIndex.ourSnapshotMappingsEnabled ? 0xFF:0) : 1;
   }
 
   @Override
diff --git a/platform/lang-impl/src/com/intellij/psi/stubs/StubIndexImpl.java b/platform/lang-impl/src/com/intellij/psi/stubs/StubIndexImpl.java
index 6cb43283952f..fc17bf25a33f 100644
--- a/platform/lang-impl/src/com/intellij/psi/stubs/StubIndexImpl.java
+++ b/platform/lang-impl/src/com/intellij/psi/stubs/StubIndexImpl.java
@@ -135,7 +135,7 @@ public class StubIndexImpl extends StubIndex implements ApplicationComponent, Pe
         LOG.info("Version has changed for stub index " + extension.getKey() + ". The index will be rebuilt.");
       }
       FileUtil.delete(indexRootDir);
-      IndexingStamp.rewriteVersion(versionFile, version);
+      IndexingStamp.rewriteVersion(versionFile, version); // todo snapshots indices
     }
 
     for (int attempt = 0; attempt < 2; attempt++) {
@@ -157,7 +157,7 @@ public class StubIndexImpl extends StubIndex implements ApplicationComponent, Pe
         LOG.info(e);
         needRebuild = true;
         FileUtil.delete(indexRootDir);
-        IndexingStamp.rewriteVersion(versionFile, version);
+        IndexingStamp.rewriteVersion(versionFile, version); // todo snapshots indices
       }
     }
     return needRebuild;
@@ -445,7 +445,7 @@ public class StubIndexImpl extends StubIndex implements ApplicationComponent, Pe
   }
 
   private static class MyIndex<K> extends MapReduceIndex<K, StubIdList, Void> {
-    public MyIndex(final IndexStorage<K, StubIdList> storage) {
+    public MyIndex(final IndexStorage<K, StubIdList> storage) throws IOException {
       super(null, null, storage);
     }
 
diff --git a/platform/lang-impl/src/com/intellij/psi/stubs/StubUpdatingIndex.java b/platform/lang-impl/src/com/intellij/psi/stubs/StubUpdatingIndex.java
index 0b565e657cd7..58d562543b1c 100644
--- a/platform/lang-impl/src/com/intellij/psi/stubs/StubUpdatingIndex.java
+++ b/platform/lang-impl/src/com/intellij/psi/stubs/StubUpdatingIndex.java
@@ -227,7 +227,7 @@ public class StubUpdatingIndex extends CustomImplementationFileBasedIndexExtensi
   @NotNull
   @Override
   public UpdatableIndex<Integer, SerializedStubTree, FileContent> createIndexImplementation(@NotNull final ID<Integer, SerializedStubTree> indexId, @NotNull final FileBasedIndex owner, @NotNull IndexStorage<Integer, SerializedStubTree> storage)
-    throws StorageException {
+    throws StorageException, IOException {
     if (storage instanceof MemoryIndexStorage) {
       final MemoryIndexStorage<Integer, SerializedStubTree> memStorage = (MemoryIndexStorage<Integer, SerializedStubTree>)storage;
       memStorage.addBufferingStateListener(new MemoryIndexStorage.BufferingStateListener() {
@@ -273,7 +273,8 @@ public class StubUpdatingIndex extends CustomImplementationFileBasedIndexExtensi
   private class MyIndex extends MapReduceIndex<Integer, SerializedStubTree, FileContent> {
     private StubIndexImpl myStubIndex;
 
-    public MyIndex(final ID<Integer, SerializedStubTree> indexId, final IndexStorage<Integer, SerializedStubTree> storage, final DataIndexer<Integer, SerializedStubTree, FileContent> indexer) throws StorageException {
+    public MyIndex(final ID<Integer, SerializedStubTree> indexId, final IndexStorage<Integer, SerializedStubTree> storage, final DataIndexer<Integer, SerializedStubTree, FileContent> indexer)
+      throws StorageException, IOException {
       super(indexId, indexer, storage);
       checkNameStorage();
     }
diff --git a/platform/lang-impl/src/com/intellij/util/indexing/ByteSequenceDataExternalizer.java b/platform/lang-impl/src/com/intellij/util/indexing/ByteSequenceDataExternalizer.java
new file mode 100644
index 000000000000..216ad325bee3
--- /dev/null
+++ b/platform/lang-impl/src/com/intellij/util/indexing/ByteSequenceDataExternalizer.java
@@ -0,0 +1,43 @@
+/*
+ * Copyright 2000-2014 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 com.intellij.util.indexing;
+
+import com.intellij.openapi.util.io.ByteSequence;
+import com.intellij.util.io.DataExternalizer;
+import org.jetbrains.annotations.NotNull;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+* Created by Maxim.Mossienko on 5/7/2014.
+*/
+class ByteSequenceDataExternalizer implements DataExternalizer<ByteSequence> {
+  static final ByteSequenceDataExternalizer INSTANCE = new ByteSequenceDataExternalizer();
+  @Override
+  public void save(@NotNull DataOutput out, ByteSequence value) throws IOException {
+    out.write(value.getBytes(), value.getOffset(), value.getLength()); // todo fix double copying
+  }
+
+  @Override
+  public ByteSequence read(@NotNull DataInput in) throws IOException {
+    byte[] buf = new byte[((InputStream)in).available()]; // todo fix double copying
+    in.readFully(buf);
+    return new ByteSequence(buf);
+  }
+}
diff --git a/platform/lang-impl/src/com/intellij/util/indexing/ContentHashesSupport.java b/platform/lang-impl/src/com/intellij/util/indexing/ContentHashesSupport.java
index 6607745d5b44..40e5d26e702e 100644
--- a/platform/lang-impl/src/com/intellij/util/indexing/ContentHashesSupport.java
+++ b/platform/lang-impl/src/com/intellij/util/indexing/ContentHashesSupport.java
@@ -15,9 +15,7 @@
  */
 package com.intellij.util.indexing;
 
-import com.intellij.openapi.application.PathManager;
 import com.intellij.openapi.fileTypes.FileType;
-import com.intellij.openapi.util.ThrowableComputable;
 import com.intellij.openapi.vfs.newvfs.persistent.ContentHashesUtil;
 import com.intellij.openapi.vfs.newvfs.persistent.FlushingDaemon;
 import com.intellij.util.io.IOUtil;
@@ -33,28 +31,27 @@ import java.security.MessageDigest;
  * @since 4/10/2014.
  */
 class ContentHashesSupport {
-  private static final ContentHashesUtil.HashEnumerator ourHashesWithFileType;
+  private static volatile ContentHashesUtil.HashEnumerator ourHashesWithFileType;
 
-  static {
-    ContentHashesUtil.HashEnumerator hashEnumerator = null;
-    try {
-      final File hashEnumeratorFile = new File(PathManager.getIndexRoot(), "hashesWithFileType");
-      hashEnumerator = IOUtil.openCleanOrResetBroken(new ThrowableComputable<ContentHashesUtil.HashEnumerator, IOException>() {
-        @Override
-        public ContentHashesUtil.HashEnumerator compute() throws IOException {
-          return new ContentHashesUtil.HashEnumerator(hashEnumeratorFile, null);
-        }
-      }, hashEnumeratorFile);
-      FlushingDaemon.everyFiveSeconds(new Runnable() {
-        @Override
-        public void run() {
-          if (ourHashesWithFileType.isDirty()) ourHashesWithFileType.force();
-        }
-      });
-    } catch (IOException ex) {
-      throw new RuntimeException(ex);
-    } finally {
-      ourHashesWithFileType = hashEnumerator;
+  static void initContentHashesEnumerator() throws IOException {
+    if (ourHashesWithFileType != null) return;
+    synchronized (ContentHashesSupport.class) {
+      if (ourHashesWithFileType != null) return;
+      ContentHashesUtil.HashEnumerator hashEnumerator = null;
+      final File hashEnumeratorFile = new File(IndexInfrastructure.getPersistentIndexRoot(), "hashesWithFileType");
+      try {
+        hashEnumerator = new ContentHashesUtil.HashEnumerator(hashEnumeratorFile, null);
+        FlushingDaemon.everyFiveSeconds(new Runnable() {
+          @Override
+          public void run() {
+            if (ourHashesWithFileType.isDirty()) ourHashesWithFileType.force();
+          }
+        });
+        ourHashesWithFileType = hashEnumerator;
+      } catch (IOException ex) {
+        IOUtil.deleteAllFilesStartingWith(hashEnumeratorFile);
+        throw ex;
+      }
     }
   }
 
diff --git a/platform/lang-impl/src/com/intellij/util/indexing/CustomImplementationFileBasedIndexExtension.java b/platform/lang-impl/src/com/intellij/util/indexing/CustomImplementationFileBasedIndexExtension.java
index d504daf8e808..e0e5d8e79db8 100644
--- a/platform/lang-impl/src/com/intellij/util/indexing/CustomImplementationFileBasedIndexExtension.java
+++ b/platform/lang-impl/src/com/intellij/util/indexing/CustomImplementationFileBasedIndexExtension.java
@@ -21,8 +21,10 @@ package com.intellij.util.indexing;
 
 import org.jetbrains.annotations.NotNull;
 
+import java.io.IOException;
+
 public abstract class CustomImplementationFileBasedIndexExtension<K, V, I> extends FileBasedIndexExtension<K, V> {
   @NotNull
   public abstract UpdatableIndex<K, V, I> createIndexImplementation(@NotNull ID<K, V> indexId, @NotNull FileBasedIndex owner, @NotNull IndexStorage<K, V> storage)
-    throws StorageException;
+    throws StorageException, IOException;
 }
\ No newline at end of file
diff --git a/platform/lang-impl/src/com/intellij/util/indexing/FileBasedIndexImpl.java b/platform/lang-impl/src/com/intellij/util/indexing/FileBasedIndexImpl.java
index f9593ebcf58a..41f6fcb83409 100644
--- a/platform/lang-impl/src/com/intellij/util/indexing/FileBasedIndexImpl.java
+++ b/platform/lang-impl/src/com/intellij/util/indexing/FileBasedIndexImpl.java
@@ -381,7 +381,10 @@ public class FileBasedIndexImpl extends FileBasedIndex {
         versionChanged = true;
         LOG.info("Version has changed for index " + name + ". The index will be rebuilt.");
       }
-      FileUtil.delete(IndexInfrastructure.getIndexRootDir(name));
+      if (extension.hasSnapshotMapping() && (isCurrentVersionCorrupted || versionChanged)) {
+        safeDelete(IndexInfrastructure.getPersistentIndexRootDir(name));
+      }
+      safeDelete(IndexInfrastructure.getIndexRootDir(name));
       IndexingStamp.rewriteVersion(versionFile, version);
     }
 
@@ -394,8 +397,14 @@ public class FileBasedIndexImpl extends FileBasedIndex {
     throws IOException {
     MapIndexStorage<K, V> storage = null;
     final ID<K, V> name = extension.getName();
+    boolean contentHashesEnumeratorOk = false;
+
     for (int attempt = 0; attempt < 2; attempt++) {
       try {
+        if (extension.hasSnapshotMapping()) {
+          ContentHashesSupport.initContentHashesEnumerator();
+          contentHashesEnumeratorOk = true;
+        }
         storage = new MapIndexStorage<K, V>(
           IndexInfrastructure.getStorageFile(name),
           extension.getKeyDescriptor(),
@@ -443,6 +452,7 @@ public class FileBasedIndexImpl extends FileBasedIndex {
       }
       catch (Exception e) {
         LOG.info(e);
+        boolean instantiatedStorage = storage != null;
         try {
           if (storage != null) storage.close();
           storage = null;
@@ -450,12 +460,22 @@ public class FileBasedIndexImpl extends FileBasedIndex {
         catch (Exception ignored) {
         }
 
-        FileUtil.delete(IndexInfrastructure.getIndexRootDir(name));
+        safeDelete(IndexInfrastructure.getIndexRootDir(name));
+
+        if (extension.hasSnapshotMapping() && (!contentHashesEnumeratorOk || instantiatedStorage)) {
+          safeDelete(IndexInfrastructure.getPersistentIndexRootDir(name)); // todo there is possibility of corruption of storage and content hashes
+        }
         IndexingStamp.rewriteVersion(versionFile, version);
       }
     }
   }
 
+  private static boolean safeDelete(File dir) {
+    File directory = FileUtil.findSequentNonexistentFile(dir.getParentFile(), dir.getName(), "");
+    boolean success = dir.renameTo(directory);
+    return FileUtil.delete(success ? directory:dir);
+  }
+
   private static void saveRegisteredIndices(@NotNull Collection<ID<?, ?>> ids) {
     final File file = getRegisteredIndicesFile();
     try {
@@ -519,7 +539,7 @@ public class FileBasedIndexImpl extends FileBasedIndex {
         extension.hasSnapshotMapping() && IdIndex.ourSnapshotMappingsEnabled
         ? createInputsIndexExternalizer(extension, indexId, extension.getKeyDescriptor())
         : null;
-      index = new MapReduceIndex<K, V, FileContent>(indexId, extension.getIndexer(), storage, externalizer);
+      index = new MapReduceIndex<K, V, FileContent>(indexId, extension.getIndexer(), storage, externalizer, extension.getValueExternalizer());
     }
     index.setInputIdToDataKeysIndex(new Factory<PersistentHashMap<Integer, Collection<K>>>() {
       @Override
@@ -1620,7 +1640,7 @@ public class FileBasedIndexImpl extends FileBasedIndex {
       indicesToDrop.remove(key.toString());
     }
     for (String s : indicesToDrop) {
-      FileUtil.delete(IndexInfrastructure.getIndexRootDir(ID.create(s)));
+      safeDelete(IndexInfrastructure.getIndexRootDir(ID.create(s)));
     }
   }
 
@@ -1715,7 +1735,7 @@ public class FileBasedIndexImpl extends FileBasedIndex {
             byte[] hash;
             try {
               currentBytes = content.getBytes();
-              hash = fileType.isBinary() ? null:ContentHashesSupport.calcContentHashWithFileType(currentBytes, fileType);
+              hash = fileType.isBinary() || !IdIndex.ourSnapshotMappingsEnabled ? null:ContentHashesSupport.calcContentHashWithFileType(currentBytes, fileType);
             }
             catch (IOException e) {
               currentBytes = ArrayUtil.EMPTY_BYTE_ARRAY;
diff --git a/platform/lang-impl/src/com/intellij/util/indexing/IndexInfrastructure.java b/platform/lang-impl/src/com/intellij/util/indexing/IndexInfrastructure.java
index f795c3594dba..7a70278e3c33 100644
--- a/platform/lang-impl/src/com/intellij/util/indexing/IndexInfrastructure.java
+++ b/platform/lang-impl/src/com/intellij/util/indexing/IndexInfrastructure.java
@@ -36,6 +36,7 @@ import java.util.Locale;
 public class IndexInfrastructure {
   private static final boolean ourUnitTestMode = ApplicationManager.getApplication().isUnitTestMode();
   private static final String STUB_VERSIONS = ".versions";
+  private static final String PERSISTENT_INDEX_DIRECTORY_NAME = ".persistent";
 
   private IndexInfrastructure() {
   }
@@ -60,14 +61,35 @@ public class IndexInfrastructure {
     return getIndexDirectory(indexName, false);
   }
 
+  public static File getPersistentIndexRoot() {
+    File indexDir = new File(PathManager.getIndexRoot() + File.separator + PERSISTENT_INDEX_DIRECTORY_NAME);
+    indexDir.mkdirs();
+    return indexDir;
+  }
+
+  @NotNull
+  public static File getPersistentIndexRootDir(@NotNull ID<?, ?> indexName) {
+    return getIndexDirectory(indexName, false, PERSISTENT_INDEX_DIRECTORY_NAME);
+  }
+
   @NotNull
   private static File getIndexDirectory(@NotNull ID<?, ?> indexName, boolean forVersion) {
+    return getIndexDirectory(indexName, forVersion, "");
+  }
+
+  @NotNull
+  private static File getIndexDirectory(@NotNull ID<?, ?> indexName, boolean forVersion, String relativePath) {
     final String dirName = indexName.toString().toLowerCase(Locale.US);
-    // store StubIndices under StubUpdating index' root to ensure they are deleted
-    // when StubUpdatingIndex version is changed
-    final File indexDir = indexName instanceof StubIndexKey
-               ? new File(getIndexRootDir(StubUpdatingIndex.INDEX_ID), forVersion ? STUB_VERSIONS : dirName)
-               : new File(PathManager.getIndexRoot(), dirName);
+    File indexDir;
+
+    if (indexName instanceof StubIndexKey) {
+      // store StubIndices under StubUpdating index' root to ensure they are deleted
+      // when StubUpdatingIndex version is changed
+      indexDir = new File(getIndexDirectory(StubUpdatingIndex.INDEX_ID, false, relativePath), forVersion ? STUB_VERSIONS : dirName);
+    } else {
+      if (relativePath.length() > 0) relativePath = File.separator + relativePath;
+      indexDir = new File(PathManager.getIndexRoot() + relativePath, dirName);
+    }
     indexDir.mkdirs();
     return indexDir;
   }
diff --git a/platform/lang-impl/src/com/intellij/util/indexing/MapReduceIndex.java b/platform/lang-impl/src/com/intellij/util/indexing/MapReduceIndex.java
index 3c186c925448..50bd4de6b96d 100644
--- a/platform/lang-impl/src/com/intellij/util/indexing/MapReduceIndex.java
+++ b/platform/lang-impl/src/com/intellij/util/indexing/MapReduceIndex.java
@@ -19,21 +19,22 @@ package com.intellij.util.indexing;
 import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.progress.ProgressManager;
 import com.intellij.openapi.util.*;
+import com.intellij.openapi.util.io.BufferExposingByteArrayOutputStream;
+import com.intellij.openapi.util.io.ByteSequence;
 import com.intellij.openapi.util.io.FileUtil;
 import com.intellij.psi.search.GlobalSearchScope;
 import com.intellij.util.Processor;
+import com.intellij.util.SmartList;
+import com.intellij.util.SystemProperties;
 import com.intellij.util.io.*;
+import com.intellij.util.io.DataOutputStream;
 import gnu.trove.THashMap;
 import gnu.trove.TObjectObjectProcedure;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-import java.io.File;
-import java.io.IOException;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.Map;
-import java.util.Set;
+import java.io.*;
+import java.util.*;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 
@@ -48,10 +49,12 @@ public class MapReduceIndex<Key, Value, Input> implements UpdatableIndex<Key,Val
   private final DataIndexer<Key, Value, Input> myIndexer;
   @NotNull protected final IndexStorage<Key, Value> myStorage;
   private final boolean myHasSnapshotMapping;
+
+  private final DataExternalizer<Value> myValueExternalizer;
   private final DataExternalizer<Collection<Key>> mySnapshotIndexExternalizer;
 
   private PersistentHashMap<Integer, Collection<Key>> myInputsIndex;
-  private PersistentHashMap<Integer, Collection<Key>> mySnapshotMapping;
+  private final PersistentHashMap<Integer, ByteSequence> myContents;
   private PersistentHashMap<Integer, Integer> myInputsSnapshotMapping;
 
   private final ReentrantReadWriteLock myLock = new ReentrantReadWriteLock();
@@ -60,19 +63,34 @@ public class MapReduceIndex<Key, Value, Input> implements UpdatableIndex<Key,Val
 
   public MapReduceIndex(@Nullable final ID<Key, Value> indexId,
                         DataIndexer<Key, Value, Input> indexer,
-                        @NotNull IndexStorage<Key, Value> storage) {
-    this(indexId, indexer, storage, null);
+                        @NotNull IndexStorage<Key, Value> storage) throws IOException {
+    this(indexId, indexer, storage, null, null);
   }
 
   public MapReduceIndex(@Nullable final ID<Key, Value> indexId,
                         DataIndexer<Key, Value, Input> indexer,
                         @NotNull IndexStorage<Key, Value> storage,
-                        DataExternalizer<Collection<Key>> snapshotIndexExternalizer) {
+                        DataExternalizer<Collection<Key>> snapshotIndexExternalizer,
+                        DataExternalizer<Value> valueDataExternalizer) throws IOException {
     myIndexId = indexId;
     myIndexer = indexer;
     myStorage = storage;
     myHasSnapshotMapping = snapshotIndexExternalizer != null;
+
     mySnapshotIndexExternalizer = snapshotIndexExternalizer;
+    myValueExternalizer = valueDataExternalizer;
+    final File saved = myHasSnapshotMapping && myIndexId != null ? new File(IndexInfrastructure.getPersistentIndexRootDir(myIndexId), "values") : null;
+
+    if (saved != null) {
+      try {
+        myContents = new PersistentHashMap<Integer, ByteSequence>(saved, EnumeratorIntegerDescriptor.INSTANCE, ByteSequenceDataExternalizer.INSTANCE);
+      } catch (IOException ex) {
+        IOUtil.deleteAllFilesStartingWith(saved);
+        throw ex;
+      }
+    } else {
+      myContents = null;
+    }
   }
 
   @NotNull
@@ -93,10 +111,6 @@ public class MapReduceIndex<Key, Value, Input> implements UpdatableIndex<Key,Val
         cleanMapping(myInputsSnapshotMapping);
         myInputsSnapshotMapping = createInputSnapshotMapping();
       }
-      if (mySnapshotMapping != null) {
-        cleanMapping(mySnapshotMapping);
-        mySnapshotMapping = createSnapshotMappingIndex();
-      }
     }
     catch (StorageException e) {
       LOG.error(e);
@@ -112,17 +126,19 @@ public class MapReduceIndex<Key, Value, Input> implements UpdatableIndex<Key,Val
   private PersistentHashMap<Integer, Integer> createInputSnapshotMapping() throws IOException {
     assert myIndexId != null;
     final File fileIdToHashIdFile = new File(IndexInfrastructure.getIndexRootDir(myIndexId), "fileIdToHashId");
-    return IOUtil.openCleanOrResetBroken(new ThrowableComputable<PersistentHashMap<Integer, Integer>, IOException>() {
-      @Override
-      public PersistentHashMap<Integer, Integer> compute() throws IOException {
-        return new PersistentHashMap<Integer, Integer>(fileIdToHashIdFile, EnumeratorIntegerDescriptor.INSTANCE, EnumeratorIntegerDescriptor.INSTANCE, 4096) {
-          @Override
-          protected boolean wantCompactIntegralValues() {
-            return true;
-          }
-        };
-      }
-    }, fileIdToHashIdFile);
+    try {
+      return new PersistentHashMap<Integer, Integer>(fileIdToHashIdFile, EnumeratorIntegerDescriptor.INSTANCE,
+                                                     EnumeratorIntegerDescriptor.INSTANCE, 4096) {
+        @Override
+        protected boolean wantCompactIntegralValues() {
+          return true;
+        }
+      };
+    }
+    catch (IOException ex) {
+      IOUtil.deleteAllFilesStartingWith(fileIdToHashIdFile);
+      throw ex;
+    }
   }
 
   private static void cleanMapping(@NotNull PersistentHashMap<?, ?> index) {
@@ -142,7 +158,7 @@ public class MapReduceIndex<Key, Value, Input> implements UpdatableIndex<Key,Val
       getReadLock().lock();
       doForce(myInputsIndex);
       doForce(myInputsSnapshotMapping);
-      doForce(mySnapshotMapping);
+      doForce(myContents);
       myStorage.flush();
     }
     catch (IOException e) {
@@ -179,7 +195,7 @@ public class MapReduceIndex<Key, Value, Input> implements UpdatableIndex<Key,Val
       finally {
         doClose(myInputsIndex);
         doClose(myInputsSnapshotMapping);
-        doClose(mySnapshotMapping);
+        doClose(myContents);
       }
     }
     catch (StorageException e) {
@@ -242,22 +258,10 @@ public class MapReduceIndex<Key, Value, Input> implements UpdatableIndex<Key,Val
     myInputsIndexFactory = factory;
     if (myHasSnapshotMapping) {
       myInputsSnapshotMapping = createInputSnapshotMapping();
-      mySnapshotMapping = createSnapshotMappingIndex();
     }
     myInputsIndex = createInputsIndex();
   }
 
-  private PersistentHashMap<Integer, Collection<Key>> createSnapshotMappingIndex() throws IOException {
-    assert myIndexId != null;
-    final File hashIdToKeysFile = new File(IndexInfrastructure.getIndexRootDir(myIndexId), "hashIdToKeys");
-    return IOUtil.openCleanOrResetBroken(new ThrowableComputable<PersistentHashMap<Integer, Collection<Key>>, IOException>() {
-      @Override
-      public PersistentHashMap<Integer, Collection<Key>> compute() throws IOException {
-        return new PersistentHashMap<Integer, Collection<Key>>(hashIdToKeysFile, EnumeratorIntegerDescriptor.INSTANCE, mySnapshotIndexExternalizer);
-      }
-    }, hashIdToKeysFile);
-  }
-
   @Nullable
   private PersistentHashMap<Integer, Collection<Key>> createInputsIndex() throws IOException {
     Factory<PersistentHashMap<Integer, Collection<Key>>> factory = myInputsIndexFactory;
@@ -275,40 +279,64 @@ public class MapReduceIndex<Key, Value, Input> implements UpdatableIndex<Key,Val
     return null;
   }
 
+  private static final boolean doReadSavedPersistentData = SystemProperties.getBooleanProperty("idea.read.saved.persistent.index", false);
   @NotNull
   @Override
   public final Computable<Boolean> update(final int inputId, @Nullable Input content) {
+    final boolean weProcessPhysicalContent = content == null ||
+                                             (content instanceof FileContent &&
+                                              ((FileContent)content).getUserData(FileBasedIndexImpl.ourPhysicalContentKey) != null);
 
-    final Map<Key, Value> data = content != null ? myIndexer.map(content) : Collections.<Key, Value>emptyMap();
+    Map<Key, Value> data = null;
+    boolean havePersistentData = false;
+    Integer hashId = null;
 
+    if (myContents != null && weProcessPhysicalContent && content != null) {
+      try {
+        hashId = getHashOfContent((FileContent)content);
+        if (doReadSavedPersistentData) {
+          ByteSequence bytes = myContents.get(hashId);
+          if (bytes != null) {
+            data = deserializeSavedPersistentData(bytes);
+            havePersistentData = true;
+          }
+        } else {
+          havePersistentData = myContents.containsMapping(hashId);
+        }
+      } catch (IOException ex) {
+        // todo:
+        throw new RuntimeException(ex);
+      }
+    }
+
+    if (data == null) data = content != null ? myIndexer.map(content) : Collections.<Key, Value>emptyMap();
+
+    if (hashId != null && !havePersistentData && data.size() > 0) {
+      savePersistentData(data, hashId);
+    }
     ProgressManager.checkCanceled();
 
     final NotNullComputable<Collection<Key>> oldKeysGetter;
     final int savedInputId;
-
-    boolean weProcessPhysicalContent = content == null ||
-                                       (content instanceof FileContent &&
-                                        ((FileContent)content).getUserData(FileBasedIndexImpl.ourPhysicalContentKey) != null);
-
     if (myHasSnapshotMapping && weProcessPhysicalContent) {
-      try { // optimistically (out of index update write section) read current snapshot keys for file
-        final Integer hashId = myInputsSnapshotMapping.get(inputId);
-        final Collection<Key> keys = hashId != null ? mySnapshotMapping.get(hashId): null;
+      try {
 
         oldKeysGetter = new NotNullComputable<Collection<Key>>() {
-        @NotNull
-        @Override
-        public Collection<Key> compute() {
+          @NotNull
+          @Override
+          public Collection<Key> compute() {
             try {
               Integer currentHashId = myInputsSnapshotMapping.get(inputId);
               Collection<Key> currentKeys;
-              if ((currentHashId == null && hashId == null)  || (currentHashId != null && currentHashId.equals(hashId))) {
-                currentKeys = keys;
-              } else { // optimistic reading file's current keys failed
-                currentKeys = currentHashId != null ? mySnapshotMapping.get(currentHashId): null;
+              if (currentHashId != null) {
+                ByteSequence byteSequence = myContents.get(currentHashId);
+                currentKeys = byteSequence != null ? deserializeSavedPersistentData(byteSequence).keySet() : Collections.<Key>emptyList();
+              }
+              else {
+                currentKeys = Collections.emptyList();
               }
 
-              return currentKeys == null ? Collections.<Key>emptyList() : currentKeys;
+              return currentKeys;
             } catch (IOException e) {
               throw new RuntimeException(e);
             }
@@ -316,22 +344,7 @@ public class MapReduceIndex<Key, Value, Input> implements UpdatableIndex<Key,Val
         };
 
         if (content instanceof FileContent) {
-          FileContent fileContent = (FileContent)content;
-          Integer previouslyCalculatedContentHashId = fileContent.getUserData(ourSavedContentHashIdKey);
-          if (previouslyCalculatedContentHashId == null) {
-            byte[] hash = fileContent instanceof FileContentImpl ? ((FileContentImpl)fileContent).getHash():null;
-            if (hash == null) {
-              previouslyCalculatedContentHashId = ContentHashesSupport.calcContentHashIdWithFileType(fileContent.getContent(), fileContent.getFileType());
-            } else {
-              previouslyCalculatedContentHashId =  ContentHashesSupport.enumerateHash(hash);
-            }
-            fileContent.putUserData(ourSavedContentHashIdKey, previouslyCalculatedContentHashId);
-          }
-
-          savedInputId = previouslyCalculatedContentHashId;
-          if (!mySnapshotMapping.containsMapping(savedInputId)) { // save current snapshot keys out of index update write section
-            mySnapshotMapping.put(savedInputId, data.keySet());
-          }
+          savedInputId = getHashOfContent((FileContent)content);
         } else {
           savedInputId = NULL_MAPPING;
         }
@@ -356,6 +369,7 @@ public class MapReduceIndex<Key, Value, Input> implements UpdatableIndex<Key,Val
     }
 
     // do not depend on content!
+    final Map<Key, Value> finalData = data;
     return new Computable<Boolean>() {
       @Override
       public Boolean compute() {
@@ -364,7 +378,7 @@ public class MapReduceIndex<Key, Value, Input> implements UpdatableIndex<Key,Val
           @Override
           public void run() {
             try {
-              updateWithMap(inputId, savedInputId, data, oldKeysGetter);
+              updateWithMap(inputId, savedInputId, finalData, oldKeysGetter);
             }
             catch (StorageException ex) {
               exRef.set(ex);
@@ -383,6 +397,74 @@ public class MapReduceIndex<Key, Value, Input> implements UpdatableIndex<Key,Val
     };
   }
 
+  private Map<Key, Value> deserializeSavedPersistentData(ByteSequence bytes) throws IOException {
+    DataInputStream stream = new DataInputStream(new UnsyncByteArrayInputStream(bytes.getBytes(), bytes.getOffset(), bytes.getLength()));
+    int pairs = DataInputOutputUtil.readINT(stream);
+    if (pairs == 0) return Collections.emptyMap();
+    Map<Key, Value> result = new THashMap<Key, Value>(pairs);
+    while (stream.available() > 0) {
+      Value value = myValueExternalizer.read(stream);
+      Collection<Key> keys = mySnapshotIndexExternalizer.read(stream);
+      for(Key k:keys) result.put(k, value);
+    }
+    return result;
+  }
+
+  private static Integer getHashOfContent(FileContent content) throws IOException {
+    Integer previouslyCalculatedContentHashId = content.getUserData(ourSavedContentHashIdKey);
+    if (previouslyCalculatedContentHashId == null) {
+      byte[] hash = content instanceof FileContentImpl ? ((FileContentImpl)content).getHash():null;
+      if (hash == null) {
+        previouslyCalculatedContentHashId = ContentHashesSupport
+          .calcContentHashIdWithFileType(content.getContent(), content.getFileType());
+      } else {
+        previouslyCalculatedContentHashId =  ContentHashesSupport.enumerateHash(hash);
+      }
+      content.putUserData(ourSavedContentHashIdKey, previouslyCalculatedContentHashId);
+    }
+    return previouslyCalculatedContentHashId;
+  }
+
+  private static final ThreadLocalCachedByteArray ourSpareByteArray = new ThreadLocalCachedByteArray();
+
+  private void savePersistentData(Map<Key, Value> data, int id) {
+    try {
+      BufferExposingByteArrayOutputStream out = new BufferExposingByteArrayOutputStream(ourSpareByteArray.getBuffer(4 * data.size()));
+      DataOutputStream stream = new DataOutputStream(out);
+      int size = data.size();
+      DataInputOutputUtil.writeINT(stream, size);
+
+      if (size > 0) {
+        THashMap<Value, List<Key>> values = new THashMap<Value, List<Key>>();
+        List<Key> keysForNullValue = null;
+        for (Map.Entry<Key, Value> e : data.entrySet()) {
+          Value value = e.getValue();
+
+          List<Key> keys = value != null ? values.get(value):keysForNullValue;
+          if (keys == null) {
+            if (value != null) values.put(value, keys = new SmartList<Key>());
+            else keys = keysForNullValue = new SmartList<Key>();
+          }
+          keys.add(e.getKey());
+        }
+
+        if (keysForNullValue != null) {
+          myValueExternalizer.save(stream, null);
+          mySnapshotIndexExternalizer.save(stream, keysForNullValue);
+        }
+
+        for(Value value:values.keySet()) {
+          myValueExternalizer.save(stream, value);
+          mySnapshotIndexExternalizer.save(stream, values.get(value));
+        }
+      }
+
+      myContents.put(id, new ByteSequence(out.getInternalBuffer(), 0, out.size()));
+    } catch (IOException ex) {
+      throw new RuntimeException(ex);
+    }
+  }
+
   private static final com.intellij.openapi.util.Key<Integer> ourSavedContentHashIdKey = com.intellij.openapi.util.Key.create("saved.content.hash.id");
 
   protected void updateWithMap(final int inputId,
diff --git a/platform/platform-api/src/com/intellij/util/net/HttpConfigurable.java b/platform/platform-api/src/com/intellij/util/net/HttpConfigurable.java
index 4dfec8669bf9..94eaa4db1ccb 100644
--- a/platform/platform-api/src/com/intellij/util/net/HttpConfigurable.java
+++ b/platform/platform-api/src/com/intellij/util/net/HttpConfigurable.java
@@ -62,7 +62,7 @@ import java.util.*;
   },
   storageChooser = HttpConfigurable.StorageChooser.class
 )
-public class HttpConfigurable implements PersistentStateComponent<HttpConfigurable>, ApplicationComponent, JDOMExternalizable,
+public class HttpConfigurable implements PersistentStateComponent<HttpConfigurable>, ApplicationComponent,
                                          ExportableApplicationComponent {
   private static final Logger LOG = Logger.getInstance("#com.intellij.util.net.HttpConfigurable");
   public boolean PROXY_TYPE_IS_SOCKS = false;
@@ -98,6 +98,7 @@ public class HttpConfigurable implements PersistentStateComponent<HttpConfigurab
 
   @Override
   public HttpConfigurable getState() {
+    CommonProxy.isInstalledAssertion();
     final HttpConfigurable state = new HttpConfigurable();
     XmlSerializerUtil.copyBean(this, state);
     if (!KEEP_PROXY_PASSWORD) {
@@ -306,15 +307,14 @@ public class HttpConfigurable implements PersistentStateComponent<HttpConfigurab
     }
   }
 
-  //these methods are preserved for compatibility
-  @Override
+  //these methods are preserved for compatibility with com.intellij.openapi.project.impl.IdeaServerSettings
+  @Deprecated
   public void readExternal(Element element) throws InvalidDataException {
     loadState(XmlSerializer.deserialize(element, HttpConfigurable.class));
   }
 
-  @Override
+  @Deprecated
   public void writeExternal(Element element) throws WriteExternalException {
-    CommonProxy.isInstalledAssertion();
     XmlSerializer.serializeInto(getState(), element);
     if (USE_PROXY_PAC && USE_HTTP_PROXY && ! ApplicationManager.getApplication().isDisposed()) {
       ApplicationManager.getApplication().invokeLater(new Runnable() {
diff --git a/platform/projectModel-impl/src/com/intellij/openapi/components/impl/stores/DefaultStateSerializer.java b/platform/projectModel-impl/src/com/intellij/openapi/components/impl/stores/DefaultStateSerializer.java
index d6cc3b2cc4e7..890d77578a81 100644
--- a/platform/projectModel-impl/src/com/intellij/openapi/components/impl/stores/DefaultStateSerializer.java
+++ b/platform/projectModel-impl/src/com/intellij/openapi/components/impl/stores/DefaultStateSerializer.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2014 JetBrains s.r.o.
+ * Copyright 2000-2012 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.
@@ -21,6 +21,7 @@ import com.intellij.openapi.components.StorageId;
 import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.util.InvalidDataException;
 import com.intellij.openapi.util.JDOMExternalizable;
+import com.intellij.openapi.util.JDOMUtil;
 import com.intellij.openapi.util.WriteExternalException;
 import com.intellij.util.xmlb.Accessor;
 import com.intellij.util.xmlb.SkipDefaultValuesSerializationFilters;
@@ -92,7 +93,11 @@ class DefaultStateSerializer {
       //assert mergeInto == null;
       return (T)stateElement;
     }
-    else if (JDOMExternalizable.class.isAssignableFrom(stateClass) && mergeInto == null) {
+    else if (JDOMExternalizable.class.isAssignableFrom(stateClass)) {
+      if (mergeInto != null) {
+        String elementText = JDOMUtil.writeElement(stateElement, "\n");
+        LOG.error("State is " + stateClass.getName() + ", merge into is " + mergeInto.toString() + ", state element text is " + elementText);
+      }
       try {
         final T t = stateClass.newInstance();
         try {
diff --git a/plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/bugs/MismatchedStringBuilderQueryUpdateInspection.java b/plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/bugs/MismatchedStringBuilderQueryUpdateInspection.java
index 168e27628beb..025172a78ea7 100644
--- a/plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/bugs/MismatchedStringBuilderQueryUpdateInspection.java
+++ b/plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/bugs/MismatchedStringBuilderQueryUpdateInspection.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2012 Bas Leijdekkers
+ * Copyright 2011-2014 Bas Leijdekkers
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -227,12 +227,23 @@ public class MismatchedStringBuilderQueryUpdateInspection extends BaseInspection
 
     @Override
     public void visitMethodCallExpression(PsiMethodCallExpression expression) {
-      super.visitMethodCallExpression(expression);
       if (updated) {
         return;
       }
       super.visitMethodCallExpression(expression);
-      final PsiReferenceExpression methodExpression = expression.getMethodExpression();
+      checkReferenceExpression(expression.getMethodExpression());
+    }
+
+    @Override
+    public void visitMethodReferenceExpression(PsiMethodReferenceExpression expression) {
+      if (updated) {
+        return;
+      }
+      super.visitMethodReferenceExpression(expression);
+      checkReferenceExpression(expression);
+    }
+
+    private void checkReferenceExpression(PsiReferenceExpression methodExpression) {
       final String name = methodExpression.getReferenceName();
       if (!updateNames.contains(name)) {
         return;
diff --git a/plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/mismatched_string_builder_query_update/MismatchedStringBuilderQueryUpdate.java b/plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/mismatched_string_builder_query_update/MismatchedStringBuilderQueryUpdate.java
index ce84d8e173f9..c8d9fb80cf19 100644
--- a/plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/mismatched_string_builder_query_update/MismatchedStringBuilderQueryUpdate.java
+++ b/plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/mismatched_string_builder_query_update/MismatchedStringBuilderQueryUpdate.java
@@ -7,7 +7,7 @@ public class MismatchedStringBuilderQueryUpdate {
     b.append("");
     System.out.println("" + b + "");
 
-    final StringBuilder c = new StringBuilder();
+    final StringBuilder <warning descr="Contents of StringBuilder 'c' are updated, but never queried">c</warning> = new StringBuilder();
     c.append(' ');
   }
 
@@ -17,4 +17,17 @@ public class MismatchedStringBuilderQueryUpdate {
     sb.append("abc");
     return sb.reverse();
   }
+
+  void indexedList(List<String> list) {
+    StringBuilder stringBuilder = new StringBuilder(); // <--- false warning here
+    list.forEach(stringBuilder::append);
+    System.out.println(stringBuilder.toString());
+  }
+}
+interface List<T> {
+  default void forEach(Consumer<? super T> action) {
+  }
+}
+interface Consumer<T> {
+  void accept(T t);
 }
diff --git a/plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/mismatched_string_builder_query_update/expected.xml b/plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/mismatched_string_builder_query_update/expected.xml
deleted file mode 100644
index 43998eaeb786..000000000000
--- a/plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/mismatched_string_builder_query_update/expected.xml
+++ /dev/null
@@ -1,9 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<problems>
-  <problem>
-    <file>MismatchedStringBuilderQueryUpdate.java</file>
-    <line>10</line>
-    <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Mismatched query and update of StringBuilder</problem_class>
-    <description>Contents of StringBuilder &lt;code&gt;c&lt;/code&gt; are updated, but never queried #loc</description>
-  </problem>
-</problems>
\ No newline at end of file
diff --git a/plugins/InspectionGadgets/testsrc/com/siyeh/ig/bugs/MismatchedStringBuilderQueryUpdateInspectionTest.java b/plugins/InspectionGadgets/testsrc/com/siyeh/ig/bugs/MismatchedStringBuilderQueryUpdateInspectionTest.java
index 4a739a04234a..293d372d6ca6 100644
--- a/plugins/InspectionGadgets/testsrc/com/siyeh/ig/bugs/MismatchedStringBuilderQueryUpdateInspectionTest.java
+++ b/plugins/InspectionGadgets/testsrc/com/siyeh/ig/bugs/MismatchedStringBuilderQueryUpdateInspectionTest.java
@@ -1,10 +1,16 @@
 package com.siyeh.ig.bugs;
 
-import com.siyeh.ig.IGInspectionTestCase;
+import com.intellij.codeInspection.InspectionProfileEntry;
+import com.siyeh.ig.LightInspectionTestCase;
 
-public class MismatchedStringBuilderQueryUpdateInspectionTest extends IGInspectionTestCase {
+public class MismatchedStringBuilderQueryUpdateInspectionTest extends LightInspectionTestCase {
 
-  public void test() throws Exception {
-    doTest("com/siyeh/igtest/bugs/mismatched_string_builder_query_update", new MismatchedStringBuilderQueryUpdateInspection());
+  public void testMismatchedStringBuilderQueryUpdate() throws Exception {
+    doTest();
+  }
+
+  @Override
+  protected InspectionProfileEntry getInspection() {
+    return new MismatchedStringBuilderQueryUpdateInspection();
   }
 }
\ No newline at end of file
diff --git a/plugins/devkit/src/inspections/DevKitInspectionBase.java b/plugins/devkit/src/inspections/DevKitInspectionBase.java
index 9ded8e216fc0..5b58a7af8287 100644
--- a/plugins/devkit/src/inspections/DevKitInspectionBase.java
+++ b/plugins/devkit/src/inspections/DevKitInspectionBase.java
@@ -26,9 +26,12 @@ import com.intellij.psi.*;
 import com.intellij.psi.search.GlobalSearchScope;
 import com.intellij.psi.xml.*;
 import com.intellij.util.containers.ContainerUtil;
+import com.intellij.util.xml.DomFileElement;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.idea.devkit.DevKitBundle;
+import org.jetbrains.idea.devkit.dom.Dependency;
+import org.jetbrains.idea.devkit.dom.IdeaPlugin;
 import org.jetbrains.idea.devkit.module.PluginModuleType;
 import org.jetbrains.idea.devkit.util.ActionType;
 import org.jetbrains.idea.devkit.util.ComponentType;
@@ -62,7 +65,8 @@ public abstract class DevKitInspectionBase extends BaseJavaLocalInspectionTool {
 
     if (PluginModuleType.isOfType(module)) {
       return checkModule(module, psiClass, null, includeActions);
-    } else {
+    }
+    else {
       Set<PsiClass> types = null;
       final List<Module> modules = PluginModuleType.getCandidateModules(module);
       for (Module m : modules) {
@@ -78,20 +82,26 @@ public abstract class DevKitInspectionBase extends BaseJavaLocalInspectionTool {
     if (!DescriptorUtil.isPluginXml(pluginXml)) return types;
     assert pluginXml != null;
 
-    final XmlDocument document = pluginXml.getDocument();
-    assert document != null;
-
-    final XmlTag rootTag = document.getRootTag();
-    assert rootTag != null;
-
     final String qualifiedName = psiClass.getQualifiedName();
     if (qualifiedName != null) {
       final RegistrationTypeFinder finder = new RegistrationTypeFinder(psiClass, types);
 
-      DescriptorUtil.processComponents(rootTag, finder);
+      // "main" plugin.xml
+      processPluginXml(pluginXml, finder, includeActions);
 
-      if (includeActions) {
-        DescriptorUtil.processActions(rootTag, finder);
+      // <depends> plugin.xml files
+      final VirtualFile pluginXmlDirectory = pluginXml.getVirtualFile().getParent();
+      final DomFileElement<IdeaPlugin> fileElement = DescriptorUtil.getIdeaPlugin(pluginXml);
+      for (Dependency dependency : fileElement.getRootElement().getDependencies()) {
+        final String configFile = dependency.getConfigFile().getValue();
+        if (configFile != null) {
+          final VirtualFile depVirtualFile = pluginXmlDirectory.findChild(configFile);
+          if (depVirtualFile == null) continue;
+          final PsiFile depPluginXml = PsiManager.getInstance(module.getProject()).findFile(depVirtualFile);
+          if (DescriptorUtil.isPluginXml(depPluginXml)) {
+            processPluginXml((XmlFile)depPluginXml, finder, includeActions);
+          }
+        }
       }
 
       types = finder.getTypes();
@@ -100,6 +110,18 @@ public abstract class DevKitInspectionBase extends BaseJavaLocalInspectionTool {
     return types;
   }
 
+  private static void processPluginXml(XmlFile xmlFile, RegistrationTypeFinder finder, boolean includeActions) {
+    final XmlDocument document = xmlFile.getDocument();
+    if (document == null) return;
+    final XmlTag rootTag = document.getRootTag();
+    if (rootTag == null) return;
+
+    DescriptorUtil.processComponents(rootTag, finder);
+    if (includeActions) {
+      DescriptorUtil.processActions(rootTag, finder);
+    }
+  }
+
   @Nullable
   protected static PsiElement getAttValueToken(@NotNull XmlAttribute attribute) {
     final XmlAttributeValue valueElement = attribute.getValueElement();
@@ -132,13 +154,14 @@ public abstract class DevKitInspectionBase extends BaseJavaLocalInspectionTool {
     return false;
   }
 
-  static class RegistrationTypeFinder implements ComponentType.Processor, ActionType.Processor {
+
+  private static class RegistrationTypeFinder implements ComponentType.Processor, ActionType.Processor {
     private Set<PsiClass> myTypes;
     private final String myQualifiedName;
     private final PsiManager myManager;
     private final GlobalSearchScope myScope;
 
-    public RegistrationTypeFinder(PsiClass psiClass, Set<PsiClass> types) {
+    private RegistrationTypeFinder(PsiClass psiClass, Set<PsiClass> types) {
       myTypes = types;
       myQualifiedName = psiClass.getQualifiedName();
       myManager = psiClass.getManager();
diff --git a/plugins/devkit/src/util/DescriptorUtil.java b/plugins/devkit/src/util/DescriptorUtil.java
index 3a773e9e5fa9..3cf574f9ca48 100644
--- a/plugins/devkit/src/util/DescriptorUtil.java
+++ b/plugins/devkit/src/util/DescriptorUtil.java
@@ -87,7 +87,7 @@ public class DescriptorUtil {
     return getIdeaPlugin((XmlFile)file) != null;
   }
 
-  private static DomFileElement<IdeaPlugin> getIdeaPlugin(XmlFile file) {
+  public static DomFileElement<IdeaPlugin> getIdeaPlugin(XmlFile file) {
     return DomManager.getDomManager(file.getProject()).getFileElement(file, IdeaPlugin.class);
   }
 }
diff --git a/plugins/devkit/testData/inspections/componentNotRegistered/registeredActionInOptionalPluginDescriptor-optional-plugin.xml b/plugins/devkit/testData/inspections/componentNotRegistered/registeredActionInOptionalPluginDescriptor-optional-plugin.xml
new file mode 100644
index 000000000000..e2216421f271
--- /dev/null
+++ b/plugins/devkit/testData/inspections/componentNotRegistered/registeredActionInOptionalPluginDescriptor-optional-plugin.xml
@@ -0,0 +1,6 @@
+<idea-plugin>
+  <actions>
+    <action id="registeredAction" class="RegisteredAction"/>
+    <action id="registeredInnerAction" class="RegisteredAction.InnerAction"/>
+  </actions>
+</idea-plugin>
\ No newline at end of file
diff --git a/plugins/devkit/testData/inspections/componentNotRegistered/registeredActionInOptionalPluginDescriptor-plugin.xml b/plugins/devkit/testData/inspections/componentNotRegistered/registeredActionInOptionalPluginDescriptor-plugin.xml
new file mode 100644
index 000000000000..0ace22f7d835
--- /dev/null
+++ b/plugins/devkit/testData/inspections/componentNotRegistered/registeredActionInOptionalPluginDescriptor-plugin.xml
@@ -0,0 +1,5 @@
+<idea-plugin>
+  <!-- registeredActionInOptionalPluginDescriptor-optional-plugin.xml -->
+  <depends optional="true" config-file="optional-plugin.xml"/>
+  <depends optional="true" config-file="optional-plugin.xml"/>
+</idea-plugin>
\ No newline at end of file
diff --git a/plugins/devkit/testSources/inspections/ComponentNotRegisteredInspectionTest.java b/plugins/devkit/testSources/inspections/ComponentNotRegisteredInspectionTest.java
index 238c6b294877..3b365554d0c2 100644
--- a/plugins/devkit/testSources/inspections/ComponentNotRegisteredInspectionTest.java
+++ b/plugins/devkit/testSources/inspections/ComponentNotRegisteredInspectionTest.java
@@ -67,6 +67,14 @@ public class ComponentNotRegisteredInspectionTest extends LightCodeInsightFixtur
     myFixture.testHighlighting("RegisteredAction.java");
   }
 
+  public void testRegisteredActionInOptionalPluginDescriptor() {
+    setPluginXml("registeredActionInOptionalPluginDescriptor-plugin.xml");
+    myFixture.copyFileToProject("registeredActionInOptionalPluginDescriptor-optional-plugin.xml",
+                                "META-INF/optional-plugin.xml");
+
+    myFixture.testHighlighting("RegisteredAction.java");
+  }
+
   public void testUnregisteredAction() {
     setPluginXml("unregisteredAction-plugin.xml");
     myFixture.testHighlighting("UnregisteredAction.java");