GRAILS-11790 Support per-instance DelegatingMetaClass instances in Grails

Author: lhotari

grails-core/src/main/groovy/org/codehaus/groovy/grails/commons/GrailsMetaClassUtils.java

@@ -18,6 +18,7 @@
 import groovy.lang.AdaptingMetaClass;
 import groovy.lang.Closure;
 import groovy.lang.ClosureInvokingMethod;
+import groovy.lang.DelegatingMetaClass;
 import groovy.lang.ExpandoMetaClass;
 import groovy.lang.GroovyObject;
 import groovy.lang.GroovySystem;
@@ -42,6 +43,7 @@
  */
 public class GrailsMetaClassUtils {
 
+    private static final int MAX_DELEGATE_LEVELS = 10;
     private static final Log LOG = LogFactory.getLog(GrailsMetaClassUtils.class);
     private static final Object[] NO_ARGS = new Object[0];
 
@@ -162,6 +164,9 @@ public static MetaClass getMetaClass(Object instance) {
         if (instance instanceof GroovyObject) {
             GroovyObject groovyObject = (GroovyObject) instance;
             MetaClass metaClass = groovyObject.getMetaClass();
+            
+            metaClass = unwrapDelegatingMetaClass(metaClass);
+            
             if (!(metaClass instanceof ExpandoMetaClass)) {
                 metaClass = getExpandoMetaClass(instance.getClass());
                 groovyObject.setMetaClass(metaClass);
@@ -172,6 +177,14 @@ public static MetaClass getMetaClass(Object instance) {
         return getExpandoMetaClass(instance.getClass());
     }
 
+    private static MetaClass unwrapDelegatingMetaClass(MetaClass metaClass) {
+        int counter=0;
+        while(metaClass instanceof DelegatingMetaClass && counter++ < MAX_DELEGATE_LEVELS) {
+            metaClass = ((DelegatingMetaClass)metaClass).getAdaptee();
+        }
+        return metaClass;
+    }
+
     /**
      * Obtains a property of an instance if it exists
      *

grails-core/src/test/groovy/org/codehaus/groovy/grails/commons/GrailsMetaClassUtilsSpec.groovy

@@ -0,0 +1,26 @@
+package org.codehaus.groovy.grails.commons
+
+import spock.lang.Specification
+
+class GrailsMetaClassUtilsSpec extends Specification {
+    static {
+        ExpandoMetaClass.enableGlobally()
+    }
+        
+    def "delegating metaclass shouldn't be replaced"() {
+        given:
+        def obj = new MySampleClass(name: 'John Doe')
+        def dmc = new DelegatingMetaClass(MySampleClass)
+        obj.metaClass = dmc
+        when:
+        MetaClass mc = GrailsMetaClassUtils.getMetaClass(obj)
+        then:
+        mc instanceof ExpandoMetaClass
+        obj.getMetaClass().getAdaptee() == dmc 
+    }
+
+}
+
+class MySampleClass {
+    String name    
+}