public static void doActualPsiChange(@NotNull final PsiFile file, final DiffLog diffLog) {
    file.getViewProvider().beforeContentsSynchronized();

    try {
      final Document document = file.getViewProvider().getDocument();
      PsiDocumentManagerImpl documentManager =
          (PsiDocumentManagerImpl) PsiDocumentManager.getInstance(file.getProject());
      PsiToDocumentSynchronizer.DocumentChangeTransaction transaction =
          documentManager.getSynchronizer().getTransaction(document);

      final PsiFileImpl fileImpl = (PsiFileImpl) file;

      if (transaction == null) {
        final PomModel model = PomManager.getModel(fileImpl.getProject());

        model.runTransaction(
            new PomTransactionBase(fileImpl, model.getModelAspect(TreeAspect.class)) {
              @Override
              public PomModelEvent runInner() {
                return new TreeAspectEvent(model, diffLog.performActualPsiChange(file));
              }
            });
      } else {
        diffLog.performActualPsiChange(file);
      }
    } catch (IncorrectOperationException e) {
      LOG.error(e);
    }
  }
 @Override
 public void reparseRange(PsiFile file, int startOffset, int endOffset, CharSequence newTextS)
     throws IncorrectOperationException {
   LOG.assertTrue(file.isValid());
   final PsiFileImpl psiFile = (PsiFileImpl) file;
   final Document document = psiFile.getViewProvider().getDocument();
   assert document != null;
   document.replaceString(startOffset, endOffset, newTextS);
   PsiDocumentManager.getInstance(psiFile.getProject()).commitDocument(document);
 }
  /**
   * This method searches ast node that could be reparsed incrementally and returns pair of target
   * reparseable node and new replacement node. Returns null if there is no any chance to make
   * incremental parsing.
   */
  @Nullable
  public Couple<ASTNode> findReparseableRoots(
      @NotNull PsiFileImpl file,
      @NotNull TextRange changedPsiRange,
      @NotNull CharSequence newFileText) {
    Project project = file.getProject();
    final FileElement fileElement = file.getTreeElement();
    final CharTable charTable = fileElement.getCharTable();
    int lengthShift = newFileText.length() - fileElement.getTextLength();

    if (fileElement.getElementType() instanceof ITemplateDataElementType || isTooDeep(file)) {
      // unable to perform incremental reparse for template data in JSP, or in exceptionally deep
      // trees
      return null;
    }

    final ASTNode leafAtStart =
        fileElement.findLeafElementAt(Math.max(0, changedPsiRange.getStartOffset() - 1));
    final ASTNode leafAtEnd =
        fileElement.findLeafElementAt(
            Math.min(changedPsiRange.getEndOffset(), fileElement.getTextLength() - 1));
    ASTNode node =
        leafAtStart != null && leafAtEnd != null
            ? TreeUtil.findCommonParent(leafAtStart, leafAtEnd)
            : fileElement;
    Language baseLanguage = file.getViewProvider().getBaseLanguage();

    while (node != null && !(node instanceof FileElement)) {
      IElementType elementType = node.getElementType();
      if (elementType instanceof IReparseableElementType) {
        final TextRange textRange = node.getTextRange();
        final IReparseableElementType reparseable = (IReparseableElementType) elementType;

        if (baseLanguage.isKindOf(reparseable.getLanguage())
            && textRange.getLength() + lengthShift > 0) {
          final int start = textRange.getStartOffset();
          final int end = start + textRange.getLength() + lengthShift;
          if (end > newFileText.length()) {
            reportInconsistentLength(file, newFileText, node, start, end);
            break;
          }

          CharSequence newTextStr = newFileText.subSequence(start, end);

          if (reparseable.isParsable(node.getTreeParent(), newTextStr, baseLanguage, project)) {
            ASTNode chameleon = reparseable.createNode(newTextStr);
            if (chameleon != null) {
              DummyHolder holder =
                  DummyHolderFactory.createHolder(
                      file.getManager(), null, node.getPsi(), charTable);
              holder.getTreeElement().rawAddChildren((TreeElement) chameleon);

              if (holder.getTextLength() != newTextStr.length()) {
                String details =
                    ApplicationManager.getApplication().isInternal()
                        ? "text=" + newTextStr + "; treeText=" + holder.getText() + ";"
                        : "";
                LOG.error("Inconsistent reparse: " + details + " type=" + elementType);
              }

              return Couple.of(node, chameleon);
            }
          }
        }
      }
      node = node.getTreeParent();
    }
    return null;
  }