fix sync editing going crazy with a second colon in a tag name

xml/impl/src/com/intellij/codeInsight/editorActions/XmlTagNameSynchronizer.java

@@ -262,6 +262,7 @@ public class XmlTagNameSynchronizer extends CommandAdapter implements NamedCompo
       final CharSequence sequence = document.getCharsSequence();
       int start = -1;
       int end = -1;
+      boolean seenColon = false;
       for (int i = offset - 1; i >= Math.max(0, offset - 50); i--) {
         try {
           final char c = sequence.charAt(i);
@@ -270,6 +271,7 @@ public class XmlTagNameSynchronizer extends CommandAdapter implements NamedCompo
             break;
           }
           if (!XmlUtil.isValidTagNameChar(c)) break;
+          seenColon |= c == ':';
         }
         catch (IndexOutOfBoundsException e) {
           LOG.error("incorrect offset:" + i + ", initial: " + offset, new Attachment("document.txt", sequence.toString()));
@@ -279,10 +281,11 @@ public class XmlTagNameSynchronizer extends CommandAdapter implements NamedCompo
       if (start < 0) return null;
       for (int i = offset; i < Math.min(document.getTextLength(), offset + 50); i++) {
         final char c = sequence.charAt(i);
-        if (!XmlUtil.isValidTagNameChar(c)) {
+        if (!XmlUtil.isValidTagNameChar(c) || (seenColon && c == ':')) {
           end = i;
           break;
         }
+        seenColon |= c == ':';
       }
       if (end < 0 || start >= end) return null;
       return document.createRangeMarker(start, end, true);

xml/tests/src/com/intellij/codeInsight/completion/XmlSyncTagCommunityTest.java

@@ -155,6 +155,10 @@ public class XmlSyncTagCommunityTest extends XmlSyncTagTest {
     doTest("<div></div><caret></div>", "\b\b\b\b\b\b", "<div></div>");
   }
 
+  public void testDoubleColonError() {
+    doTest("<soap:some<caret>:some></soap:some:some>", "a", "<soap:somea:some></soap:somea:some>");
+  }
+
   public void testMultipleEditors() {
     myFixture.configureByText(XmlFileType.INSTANCE, "<div<caret>></div>");
     final Editor editor = EditorFactory.getInstance().createEditor(myFixture.getEditor().getDocument());