restore the assertion on modifying PSI for uncommitted document (WEB-12791)

java/java-tests/testSrc/com/intellij/psi/MiscPsiTest.java

@@ -260,4 +260,20 @@ public class MiscPsiTest extends LightCodeInsightFixtureTestCase {
     assertEquals("some.unknown.Foo<? extends String>", type.getCanonicalText());
   }
 
+  public void testNoPsiModificationsInUncommittedDocument() {
+    final PsiJavaFile file = (PsiJavaFile)myFixture.addFileToProject("a.java", "class A{}");
+    Document document = file.getViewProvider().getDocument();
+    document.insertString(0, " ");
+
+    PsiClass psiClass = file.getClasses()[0];
+    try {
+      psiClass.addBefore(PsiParserFacade.SERVICE.getInstance(getProject()).createWhiteSpaceFromText(" "), psiClass.getLBrace());
+      fail();
+    }
+    catch (IllegalStateException e) {
+      assertEquals("Attempt to modify PSI for non-committed Document!", e.getMessage());
+    }
+    assertEquals("class A{}", psiClass.getText());
+    assertEquals(" class A{}", document.getText());
+  }
 }

platform/core-impl/src/com/intellij/pom/core/impl/PomModelImpl.java

@@ -301,15 +301,30 @@ public class PomModelImpl extends UserDataHolderBase implements PomModel {
     final PsiToDocumentSynchronizer synchronizer = manager.getSynchronizer();
     final PsiElement changeScope = transaction.getChangeScope();
     LOG.assertTrue(changeScope != null);
-    BlockSupportImpl.sendBeforeChildrenChangeEvent((PsiManagerImpl)PsiManager.getInstance(myProject), changeScope, true);
-    final PsiFile containingFileByTree = getContainingFileByTree(changeScope);
 
+    final PsiFile containingFileByTree = getContainingFileByTree(changeScope);
+    if (changeScope.isPhysical() && synchronizer.toProcessPsiEvent() && isDocumentUncommitted(containingFileByTree)) {
+      // fail-fast to prevent any psi modifications that would cause psi/document text mismatch
+      // PsiToDocumentSynchronizer assertions happen inside event processing and are logged by PsiManagerImpl.fireEvent instead of being rethrown
+      // so it's important to throw something outside event processing
+      throw new IllegalStateException("Attempt to modify PSI for non-committed Document!");
+    }
+
+    BlockSupportImpl.sendBeforeChildrenChangeEvent((PsiManagerImpl)PsiManager.getInstance(myProject), changeScope, true);
     Document document = containingFileByTree == null ? null : manager.getCachedDocument(containingFileByTree);
     if(document != null) {
       synchronizer.startTransaction(myProject, document, changeScope);
     }
   }
 
+  private boolean isDocumentUncommitted(@Nullable PsiFile file) {
+    if (file == null) return false;
+
+    PsiDocumentManager manager = PsiDocumentManager.getInstance(myProject);
+    Document cachedDocument = manager.getCachedDocument(file);
+    return cachedDocument != null && manager.isUncommited(cachedDocument);
+  }
+
   @Nullable
   private static PsiFile getContainingFileByTree(@NotNull final PsiElement changeScope) {
     // there could be pseudo physical trees (JSPX/JSP/etc.) which must not translate

platform/core-impl/src/com/intellij/psi/impl/PsiDocumentManagerBase.java

@@ -699,7 +699,7 @@ public abstract class PsiDocumentManagerBase extends PsiDocumentManager implemen
     }
 
     // we can end up outside write action here if the document has forUseInNonAWTThread=true
-    ApplicationManager.getApplication().runWriteAction(new Runnable() {
+    ApplicationManager.getApplication().runWriteAction(new ExternalChangeAction() {
       @Override
       public void run() {
         psiFile.getViewProvider().beforeContentsSynchronized();

platform/core-impl/src/com/intellij/psi/impl/PsiToDocumentSynchronizer.java

@@ -74,10 +74,8 @@ public class PsiToDocumentSynchronizer extends PsiTreeChangeAdapter {
     final PsiFile psiFile = event.getFile();
     if (psiFile == null || psiFile.getNode() == null) return;
 
-    final Document document = getCachedDocument(psiFile, force);
-    if (document == null) return;
-
-    if (myPsiDocumentManager.isUncommited(document)) {
+    final Document document = myPsiDocumentManager.getCachedDocument(psiFile);
+    if (document != null && myPsiDocumentManager.isUncommited(document)) {
       throw new IllegalStateException("Attempt to modify PSI for non-committed Document!");
     }
   }
@@ -207,7 +205,7 @@ public class PsiToDocumentSynchronizer extends PsiTreeChangeAdapter {
     return myIgnorePsiEvents;
   }
 
-  private boolean toProcessPsiEvent() {
+  public boolean toProcessPsiEvent() {
     return !myIgnorePsiEvents && !ApplicationManager.getApplication().hasWriteAction(IgnorePsiEventsMarker.class);
   }