DomUtil.hasXml: use DomElement.exists() to avoid costly getXmlElement()

fixes + tests CR-IC-4788

xml/dom-impl/src/com/intellij/util/xml/impl/CollectionElementInvocationHandler.java

@@ -65,6 +65,7 @@ public class CollectionElementInvocationHandler extends DomInvocationHandler<Abs
     if (tag == null) return;
 
     getManager().cacheHandler(getCacheKey(), tag, null);
+    setXmlElement(null);
     deleteTag(tag);
     getManager().fireEvent(new DomEvent(parent, false));
   }

xml/dom-impl/src/com/intellij/util/xml/impl/DomInvocationHandler.java

@@ -80,7 +80,7 @@ public abstract class DomInvocationHandler<T extends AbstractDomChildDescription
   private final InvocationCache myInvocationCache;
   private volatile Converter myScalarConverter = null;
   private volatile SmartFMap<Method, Invocation> myAccessorInvocations = SmartFMap.emptyMap();
-  @Nullable protected final Stub myStub;
+  @Nullable protected Stub myStub;
 
   protected DomInvocationHandler(Type type, DomParentStrategy parentStrategy,
                                  @NotNull final EvaluatedXmlName tagName,
@@ -734,6 +734,7 @@ public abstract class DomInvocationHandler<T extends AbstractDomChildDescription
 
   protected final void setXmlElement(final XmlElement element) {
     refreshGenericInfo(element != null && !isAttribute());
+    myStub = null;
     myParentStrategy = element == null ? myParentStrategy.clearXmlElement() : myParentStrategy.setXmlElement(element);
   }
 

xml/dom-impl/src/com/intellij/util/xml/impl/DomRootInvocationHandler.java

@@ -70,6 +70,12 @@ public class DomRootInvocationHandler extends DomInvocationHandler<AbstractDomCh
     return myParent.hashCode();
   }
 
+  @Override
+  public boolean exists() {
+    return getStub() != null ||
+           getXmlElement() != null;
+  }
+
   @NotNull
   public String getXmlElementNamespace() {
     return getXmlName().getNamespace(getFile(), getFile());

xml/dom-tests/tests/com/intellij/util/xml/DomBasicsTest.java

@@ -43,6 +43,18 @@ public class DomBasicsTest extends DomTestCase {
     assertEquals(fileElement.getRootElement(), fileElement.getRootElement());
   }
 
+  public void testRootElementUndefineNotExisting() {
+    final XmlFile file = createXmlFile("<a/>");
+    final DomManagerImpl manager = getDomManager();
+    final DomFileElementImpl<DomElement> fileElement = manager.getFileElement(file, DomElement.class, "a");
+    final DomElement rootElement = fileElement.getRootElement();
+    assertNotNull(rootElement);
+    assertTrue(rootElement.exists());
+
+    rootElement.undefine();
+    assertFalse(rootElement.exists());
+  }
+
   public void testElementCaching() throws Throwable {
     final MyElement element = createElement("<a><child/></a>");
     assertSame(element.getChild(), element.getChild());
@@ -167,7 +179,8 @@ public class DomBasicsTest extends DomTestCase {
 
     assertEquals(new HashSet(Arrays.asList(foo, child, collectionChild, genericChild,
                                            info.getAttributeChildrenDescriptions().get(0))),
-                 new HashSet(info.getChildrenDescriptions()));
+                 new HashSet(info.getChildrenDescriptions())
+    );
   }
 
   private void assertFixedChildDescription(final DomFixedChildDescription description,
@@ -225,7 +238,8 @@ public class DomBasicsTest extends DomTestCase {
   }
 
   private void assertCollectionPresentableName(final String expected, final String tagName, final DomNameStrategy strategy) {
-    assertEquals(expected, new CollectionChildDescriptionImpl(new XmlName(tagName), DomElement.class, null).getCommonPresentableName(strategy));
+    assertEquals(expected,
+                 new CollectionChildDescriptionImpl(new XmlName(tagName), DomElement.class, null).getCommonPresentableName(strategy));
   }
 
   private void assertFixedPresentableName(final String expected, final String tagName, final DomNameStrategy strategy) {

xml/dom-tests/tests/com/intellij/util/xml/stubs/DomStubUsingTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2012 JetBrains s.r.o.
+ * 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.
@@ -15,6 +15,7 @@
  */
 package com.intellij.util.xml.stubs;
 
+import com.intellij.openapi.command.WriteCommandAction;
 import com.intellij.openapi.vfs.VirtualFileFilter;
 import com.intellij.psi.PsiClass;
 import com.intellij.psi.PsiFile;
@@ -117,4 +118,38 @@ public class DomStubUsingTest extends DomStubTest {
     ((PsiManagerImpl)getPsiManager()).setAssertOnFileLoadingFilter(VirtualFileFilter.ALL, myTestRootDisposable);
     DomManager.getDomManager(getProject()).getFileElement(file, Foo.class);
   }
+
+  public void testStubbedElementUndefineNotExisting() {
+    final DomFileElement<Foo> fileElement = prepare("foo.xml", Foo.class);
+    final Bar bar = fileElement.getRootElement().getBars().get(0);
+
+    assertNotNull(bar);
+    assertTrue(bar.exists());
+
+    new WriteCommandAction.Simple(null) {
+      @Override
+      protected void run() throws Throwable {
+        bar.undefine();
+      }
+    }.execute().throwException();
+
+    assertFalse(bar.exists());
+  }
+
+  public void testRootElementUndefineNotExisting() {
+    final DomFileElement<Foo> fileElement = prepare("foo.xml", Foo.class);
+
+    final DomElement rootElement = fileElement.getRootElement();
+    assertNotNull(rootElement);
+    assertTrue(rootElement.exists());
+
+    new WriteCommandAction.Simple(null) {
+      @Override
+      protected void run() throws Throwable {
+        rootElement.undefine();
+      }
+    }.execute().throwException();
+
+    assertFalse(rootElement.exists());
+  }
 }