[engine] implements new strategy for reference boolean evaluation

1) return false for a null object

2) return its value for a Boolean object, or the result of the getAsBoolean() method if it exists.

3) If directive.if.emptycheck = false (true by default), stop here and return true.

4) check for emptiness:
  - return whether an array is empty.
  - return whether isEmpty() is false (covers String and all Collection classes).
  - return whether length() is zero (covers CharSequence classes other than String).
  - returns whether size() is zero.
  - return whether a Number *strictly* equals zero.

5) check for emptiness after explicit conversion methods:
  - return whether the result of getAsString() is empty (and false for a null result) if it exists.
  - return whether the result of getAsNumber() *strictly* equals zero (and false for a null result) if it exists. 





git-svn-id: https://svn.apache.org/repos/asf/velocity/engine/trunk@1783739 13f79535-47bb-0310-9956-ffa450edef68

3 files changed, 41 insertions, 18 deletions

diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/runtime/RuntimeConstants.java b/velocity-engine-core/src/main/java/org/apache/velocity/runtime/RuntimeConstants.java
index 2d1b5d91..b85c51f1 100644
--- a/velocity-engine-core/src/main/java/org/apache/velocity/runtime/RuntimeConstants.java
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/runtime/RuntimeConstants.java
@@ -76,6 +76,12 @@ public interface RuntimeConstants
     String SKIP_INVALID_ITERATOR = "directive.foreach.skip.invalid";
 
     /**
+     * An empty object (string, collection) or zero number is false.
+     * @since 2.0
+     */
+    String CHECK_EMPTY_OBJECTS = "directive.if.emptycheck";
+    
+    /**
      * Starting tag for error messages triggered by passing a parameter not allowed in the #include directive. Only string literals,
      * and references are allowed.
      */
@@ -98,7 +104,7 @@ public interface RuntimeConstants
      * @since 1.7
      */
     String PROVIDE_SCOPE_CONTROL = "provide.scope.control";
-
+    
     /*
      * ----------------------------------------------------------------------
      *  R E S O U R C E   M A N A G E R   C O N F I G U R A T I O N
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/runtime/parser/node/ASTReference.java b/velocity-engine-core/src/main/java/org/apache/velocity/runtime/parser/node/ASTReference.java
index da210371..7875020e 100644
--- a/velocity-engine-core/src/main/java/org/apache/velocity/runtime/parser/node/ASTReference.java
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/runtime/parser/node/ASTReference.java
@@ -579,7 +579,7 @@ public class ASTReference extends SimpleNode
         }
         try
         {
-            return DuckType.asBoolean(value);
+            return DuckType.asBoolean(value, rsvc.getBoolean(RuntimeConstants.CHECK_EMPTY_OBJECTS, true));
         }
         catch(Exception e)
         {
diff --git a/velocity-engine-core/src/main/java/org/apache/velocity/util/DuckType.java b/velocity-engine-core/src/main/java/org/apache/velocity/util/DuckType.java
index eb426d6e..5edfb093 100644
--- a/velocity-engine-core/src/main/java/org/apache/velocity/util/DuckType.java
+++ b/velocity-engine-core/src/main/java/org/apache/velocity/util/DuckType.java
@@ -23,9 +23,12 @@ import java.lang.reflect.Array;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.math.BigDecimal;
+import java.math.BigInteger;
 import java.util.HashMap;
 import java.util.Map;
 
+import static org.apache.velocity.runtime.parser.node.MathUtils.isZero;
+
 /**
  * Support for getAs<Type>() convention for rendering (String), evaluating (Boolean)
  * or doing math with (Number) references.
@@ -40,7 +43,9 @@ public class DuckType
         STRING("getAsString"),
         NUMBER("getAsNumber"),
         BOOLEAN("getAsBoolean"),
-        EMPTY("isEmpty");
+        EMPTY("isEmpty"),
+        LENGTH("length"),
+        SIZE("size");
 
         final String name;
         final Map<Class,Object> cache = new HashMap();
@@ -93,11 +98,6 @@ public class DuckType
             get(value, Types.NUMBER) == null;
     }
 
-    public static boolean asBoolean(Object value)
-    {
-        return asBoolean(value, true);
-    }
-
     public static boolean asBoolean(Object value, boolean coerceType)
     {
         if (value == null)
@@ -129,23 +129,37 @@ public class DuckType
             return true;
         }
 
-        // empty string
-        if (value instanceof CharSequence)
+        // empty array
+        if (value.getClass().isArray())
         {
-            return ((CharSequence)value).length() == 0;
+            return Array.getLength(value) == 0;// [] is false
         }
 
-        // isEmpty() object
+        // isEmpty() for object / string
         Object isEmpty = get(value, Types.EMPTY);
         if (isEmpty != NO_METHOD)
         {
             return (Boolean)isEmpty;
         }
 
-        // empty array
-        if (value.getClass().isArray())
+        // isEmpty() for object / other char sequences
+        Object length = get(value, Types.LENGTH);
+        if (length != NO_METHOD && length instanceof Number)
         {
-            return Array.getLength(value) == 0;// [] is false
+            return isZero((Number)length);
+        }
+
+        // size() object / collection
+        Object size = get(value, Types.SIZE);
+        if (size != NO_METHOD && size instanceof Number)
+        {
+            return isZero((Number)size);
+        }
+
+        // zero numbers are false
+        if (value instanceof Number)
+        {
+            return isZero((Number)value);
         }
 
         // null getAsString()
@@ -166,10 +180,13 @@ public class DuckType
         {
             return true;
         }
+        // zero numbers are false
+        else if (asNumber != NO_METHOD && asNumber instanceof Number)
+        {
+            return isZero((Number)asNumber);
+        }
 
-        // empty toString()
-        String string = value.toString();
-        return string == null || string.length() == 0;
+        return false;
     }
 
     public static Number asNumber(Object value)