Some tweaks to the 'substitute name into null value' patch.

src/main/java/com/samskivert/mustache/Mustache.java

@@ -39,9 +39,10 @@ public class Mustache
         /** A value to use when a variable resolves to null. If this value is null (which is the
          * default null value), an exception will be thrown. If {@link #missingIsNull} is also
          * true, this value will be used when a variable cannot be resolved.
-         * If the nullValue contains a substring "{{name}}", then this substring
-         * will be replaced by name of the variable. For example, if nullValue="?{{name}}?"
-         * and the missing variable is "foo", then string "?foo?" will be used. */
+         *
+         * <p>If the nullValue contains a substring {@code {{name}}}, then this substring will be
+         * replaced by name of the variable. For example, if nullValue is {@code ?{{name}}?} and
+         * the missing variable is {@code foo}, then string {@code ?foo?} will be used.</p> */
         public final String nullValue;
 
         /** If this value is true, missing variables will be treated like variables that return
@@ -125,6 +126,12 @@ public class Mustache
                                 this.missingIsNull, this.emptyStringIsFalse, this.loader, collector);
         }
 
+        /** Returns the value to use in the template for the null-valued property {@code name}. See
+         * {@link #nullValue} for more details. */
+        public String computeNullValue (String name) {
+            return (nullValue == null) ? null : nullValue.replace("{{name}}", name);
+        }
+
         protected Compiler (boolean escapeHTML, boolean standardsMode, String nullValue,
                             boolean missingIsNull, boolean emptyStringIsFalse, TemplateLoader loader,
                             Collector collector) {