[devkit] RegistrationIndexer: skip fast if not plugin descriptor

plugins/devkit/devkit-core/src/dom/index/RegistrationIndexer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2017 JetBrains s.r.o.
+ * Copyright 2000-2018 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.
@@ -23,6 +23,7 @@ import com.intellij.util.Function;
 import com.intellij.util.SmartList;
 import com.intellij.util.containers.FactoryMap;
 import com.intellij.util.indexing.FileContent;
+import com.intellij.util.text.CharArrayUtil;
 import com.intellij.util.xml.DomElement;
 import com.intellij.util.xml.DomFileElement;
 import com.intellij.util.xml.DomUtil;
@@ -46,6 +47,11 @@ class RegistrationIndexer {
 
   @NotNull
   Map<String, List<RegistrationEntry>> indexFile() {
+    CharSequence text = myContent.getContentAsText();
+    if (CharArrayUtil.indexOf(text, "<idea-plugin", 0) == -1) {
+      return Collections.emptyMap();
+    }
+
     final PsiFile file = myContent.getPsiFile();
     if (!(file instanceof XmlFile)) return Collections.emptyMap();