Add option to treat zero as a falsy value

In javascript implementation, zero is a falsy value and is treated as a false boolean.
An option is added (false by default) to treat zero as a falsy value as in javascript implementation.

It means that section like:

{{#zeroValue}}foo{{/zeroValue}}

will not be rendered.

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

@@ -54,6 +54,10 @@ public class Mustache
          * mustache implementation. Default is false. */
         public final boolean emptyStringIsFalse;
 
+        /** If this value is true, zero will be treated as a false value, as in JavaScript
+         * mustache implementation. Default is false. */
+        public final boolean zeroIsFalse;
+
         /** The template loader in use during this compilation. */
         public final TemplateLoader loader;
 
@@ -76,7 +80,7 @@ public class Mustache
         /** Returns a compiler that either does or does not escape HTML by default. */
         public Compiler escapeHTML (boolean escapeHTML) {
             return new Compiler(escapeHTML, this.standardsMode, this.nullValue, this.missingIsNull,
-                                this.emptyStringIsFalse, this.loader, this.collector, this.delims);
+                                this.emptyStringIsFalse, this.zeroIsFalse, this.loader, this.collector, this.delims);
         }
 
         /** Returns a compiler that either does or does not use standards mode. Standards mode
@@ -84,7 +88,7 @@ public class Mustache
          * context. */
         public Compiler standardsMode (boolean standardsMode) {
             return new Compiler(this.escapeHTML, standardsMode, this.nullValue, this.missingIsNull,
-                                this.emptyStringIsFalse, this.loader, this.collector, this.delims);
+                                this.emptyStringIsFalse, this.zeroIsFalse, this.loader, this.collector, this.delims);
         }
 
         /** Returns a compiler that will use the given value for any variable that is missing, or
@@ -92,7 +96,7 @@ public class Mustache
          * supplied default for missing keys and existing keys that return null values. */
         public Compiler defaultValue (String defaultValue) {
             return new Compiler(this.escapeHTML, this.standardsMode, defaultValue, true,
-                                this.emptyStringIsFalse, this.loader, this.collector, this.delims);
+                                this.emptyStringIsFalse, this.zeroIsFalse, this.loader, this.collector, this.delims);
         }
 
         /** Returns a compiler that will use the given value for any variable that resolves to
@@ -108,27 +112,34 @@ public class Mustache
          * </ul> */
         public Compiler nullValue (String nullValue) {
             return new Compiler(this.escapeHTML, this.standardsMode, nullValue, false,
-                                this.emptyStringIsFalse, this.loader, this.collector, this.delims);
+                                this.emptyStringIsFalse, this.zeroIsFalse, this.loader, this.collector, this.delims);
         }
 
         /** Returns a compiler that will treat empty string as a false value if parameter is true. */
         public Compiler emptyStringIsFalse (boolean emptyStringIsFalse) {
             return new Compiler(this.escapeHTML, this.standardsMode, this.nullValue,
-                                this.missingIsNull, emptyStringIsFalse, this.loader, this.collector,
+                                this.missingIsNull, emptyStringIsFalse, this.zeroIsFalse, this.loader, this.collector,
+                                this.delims);
+        }
+
+        /** Returns a compiler that will treat zero as a false value if parameter is true. */
+        public Compiler zeroIsFalse (boolean zeroIsFalse) {
+            return new Compiler(this.escapeHTML, this.standardsMode, this.nullValue,
+                                this.missingIsNull, this.emptyStringIsFalse, zeroIsFalse, this.loader, this.collector,
                                 this.delims);
         }
 
         /** Returns a compiler configured to use the supplied template loader to handle partials. */
         public Compiler withLoader (TemplateLoader loader) {
             return new Compiler(this.escapeHTML, this.standardsMode, this.nullValue,
-                                this.missingIsNull, this.emptyStringIsFalse, loader, this.collector,
+                                this.missingIsNull, this.emptyStringIsFalse, this.zeroIsFalse, loader, this.collector,
                                 this.delims);
         }
 
         /** Returns a compiler configured to use the supplied collector. */
         public Compiler withCollector (Collector collector) {
             return new Compiler(this.escapeHTML, this.standardsMode, this.nullValue,
-                                this.missingIsNull, this.emptyStringIsFalse, this.loader, collector,
+                                this.missingIsNull, this.emptyStringIsFalse, this.zeroIsFalse, this.loader, collector,
                                 this.delims);
         }
 
@@ -137,7 +148,7 @@ public class Mustache
          * opening delims and C and D are closing delims. */
         public Compiler withDelims (String delims) {
             return new Compiler(this.escapeHTML, this.standardsMode, this.nullValue,
-                                this.missingIsNull, this.emptyStringIsFalse, this.loader,
+                                this.missingIsNull, this.emptyStringIsFalse, this.zeroIsFalse, this.loader,
                                 this.collector, new Delims().updateDelims(delims));
         }
 
@@ -148,13 +159,14 @@ public class Mustache
         }
 
         protected Compiler (boolean escapeHTML, boolean standardsMode, String nullValue,
-                            boolean missingIsNull, boolean emptyStringIsFalse, TemplateLoader loader,
+                            boolean missingIsNull, boolean emptyStringIsFalse, boolean zeroIsFalse, TemplateLoader loader,
                             Collector collector, Delims delims) {
             this.escapeHTML = escapeHTML;
             this.standardsMode = standardsMode;
             this.nullValue = nullValue;
             this.missingIsNull = missingIsNull;
             this.emptyStringIsFalse = emptyStringIsFalse;
+            this.zeroIsFalse = zeroIsFalse;
             this.loader = loader;
             this.collector = collector;
             this.delims = delims;
@@ -210,7 +222,7 @@ public class Mustache
      * Returns a compiler that escapes HTML by default and does not use standards mode.
      */
     public static Compiler compiler () {
-        return new Compiler(true, false, null, true, false, FAILING_LOADER, new DefaultCollector(),
+        return new Compiler(true, false, null, true, false, false, FAILING_LOADER, new DefaultCollector(),
                             new Delims());
     }
 
@@ -698,6 +710,8 @@ public class Mustache
                 }
             } else if (_compiler.emptyStringIsFalse && "".equals(value)) {
                 // omit the section
+            } else if (value != null && value instanceof Number && ((Number) value).longValue() == 0) {
+                // omit the section
             } else {
                 executeSegs(tmpl, ctx.nest(value, 0, false, false), out);
             }

src/test/java/com/samskivert/mustache/MustacheTest.java

@@ -145,6 +145,30 @@ public class MustacheTest
         });
     }
 
+    @Test public void testSectionWithLongValueZero () {
+        test(Mustache.compiler().zeroIsFalse(true), "", "{{#foo}}test{{/foo}}", new Object() {
+            Long foo = 0L;
+        });
+    }
+
+    @Test public void testSectionWithIntegerValueZero () {
+        test(Mustache.compiler().zeroIsFalse(true), "", "{{#foo}}test{{/foo}}", new Object() {
+            Integer foo = 0;
+        });
+    }
+
+    @Test public void testSectionWithFloatValueZero () {
+        test(Mustache.compiler().zeroIsFalse(true), "", "{{#foo}}test{{/foo}}", new Object() {
+            Float foo = 0F;
+        });
+    }
+
+    @Test public void testSectionWithDoubleValueZero () {
+        test(Mustache.compiler().zeroIsFalse(true), "", "{{#foo}}test{{/foo}}", new Object() {
+            Double foo = 0D;
+        });
+    }
+
     @Test public void testMissingSection () {
         test("", "{{#foo}}{{bar}}{{/foo}}", new Object() {
             // no foo