Fix and test for GRAILS-9084 Implement asBoolean (Groovy truth) for GroovyPage.ConstantClosure

Author: lhotari

grails-test-suite-web/src/test/groovy/org/codehaus/groovy/grails/web/pages/OptionalTagBodySpec.groovy

@@ -0,0 +1,36 @@
+package org.codehaus.groovy.grails.web.pages
+
+import grails.test.AbstractGrailsEnvChangingSpec
+
+import spock.lang.Specification
+import grails.test.mixin.TestFor
+import grails.util.Environment;
+import grails.artefact.Artefact
+
+
+@TestFor(CustomTagLib)
+class OptionalTagBodySpec extends AbstractGrailsEnvChangingSpec {
+    def "Test that the existence of a body can be tested with groovy truth"(grailsEnv) {
+        when:
+            changeGrailsEnv(grailsEnv)
+            def content = applyTemplate("<a:myBody />")
+            def content2 = applyTemplate("<a:myBody>Hello</a:myBody>")
+        then:
+            content == 'nobody'
+            content2 == 'Hello'
+        where:
+            grailsEnv << grailsEnvs
+    }
+}
+@Artefact("TagLibrary")
+class CustomTagLib {
+    static namespace = "a"
+    
+    def myBody = { attrs, body ->
+        if(body) {
+            out << body()
+        } else {
+            out << 'nobody'        
+        }
+    }
+}

grails-web/src/main/groovy/org/codehaus/groovy/grails/web/pages/GroovyPage.java

@@ -47,6 +47,7 @@
 import org.codehaus.groovy.grails.web.taglib.exceptions.GrailsTagException;
 import org.codehaus.groovy.grails.web.util.CodecPrintWriter;
 import org.codehaus.groovy.grails.web.util.GrailsPrintWriter;
+import org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation;
 
 /**
  * NOTE: Based on work done by on the GSP standalone project (https://gsp.dev.java.net/)
@@ -152,6 +153,10 @@ public Object doCall(@SuppressWarnings("unused") Object[] args) {
         public Object call(Object... args) {
             return retval;
         }
+        
+        public boolean asBoolean() {
+            return DefaultTypeTransformation.castToBoolean(retval);
+        }
     }
 
     protected static final Closure<?> EMPTY_BODY_CLOSURE = new ConstantClosure(BLANK_STRING);