do not process xs:include for stub building

xml/dom-tests/testData/stubs/include.xml

@@ -0,0 +1,3 @@
+<foo>
+  <bar string="included" int="666"></bar>
+</foo>

xml/dom-tests/testData/stubs/inclusion.xml

@@ -0,0 +1,5 @@
+<foo  xmlns:xi="http://www.w3.org/2001/XInclude">
+  <xi:include href="include.xml" xpointer="xpointer(/foo/*)"/>
+  <bar string="xxx" int="666"></bar>
+  <bar></bar>
+</foo>

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

@@ -81,6 +81,16 @@ public class DomStubBuilderTest extends DomStubTest {
     assertNull(stubTree); // no stubs for invalid XML
   }
 
+  public void testInclusion() throws Exception {
+    myFixture.copyFileToProject("include.xml");
+    doBuilderTest("inclusion.xml", "File:foo\n" +
+                                   "  Element:foo\n" +
+                                   "    Element:bar\n" +
+                                   "      Attribute:string:xxx\n" +
+                                   "      Attribute:int:666\n" +
+                                   "    Element:bar\n");
+  }
+
   public static class TestExtender extends DomExtender<Bar> {
 
     @Override

xml/xml-psi-impl/src/com/intellij/xml/util/InclusionProvider.java

@@ -42,7 +42,8 @@ class InclusionProvider implements CachedValueProvider<PsiElement[]> {
 
   @NotNull
   public static PsiElement[] getIncludedTags(XmlTag xincludeTag) {
-    return CachedValuesManager.getManager(xincludeTag.getProject()).getCachedValue(xincludeTag, new InclusionProvider(xincludeTag));
+    if (XmlUtil.isStubBuilding()) return PsiElement.EMPTY_ARRAY;
+    return CachedValuesManager.getCachedValue(xincludeTag, new InclusionProvider(xincludeTag));
   }
 
   public Result<PsiElement[]> compute() {