[ISSUE-996] Support includeZero option in IF Helper

Author: clementgbcn

handlebars/src/main/java/com/github/jknack/handlebars/Handlebars.java

@@ -167,6 +167,21 @@ public static class Utils {
      */
     @SuppressWarnings("rawtypes")
     public static boolean isEmpty(final Object value) {
+      return isEmpty(value, false);
+    }
+
+    /**
+     * Evaluate the given object and return true is the object is considered empty. Nulls, empty
+     * list or array and false values are considered empty. If includeZero is false, zero values are
+     * considered empty.
+     *
+     * @param value The object value.
+     * @param includeZero If true, zero values are considered empty.
+     * @return Return true is the object is considered empty. Nulls, empty list or array and false
+     *     values are considered empty.
+     */
+    @SuppressWarnings("rawtypes")
+    public static boolean isEmpty(final Object value, Boolean includeZero) {
       if (value == null) {
         return true;
       }
@@ -185,7 +200,7 @@ public static boolean isEmpty(final Object value) {
       if (value.getClass().isArray()) {
         return Array.getLength(value) == 0;
       }
-      if (value instanceof Number) {
+      if (!includeZero && value instanceof Number) {
         return ((Number) value).doubleValue() == 0;
       }
       return false;

handlebars/src/main/java/com/github/jknack/handlebars/Options.java

@@ -670,7 +670,7 @@ public <T> T hash(final String name, final Object defaultValue) {
    * @return False if its argument is false, null or empty list/array (a "falsy" value).
    */
   public boolean isFalsy(final Object value) {
-    return Handlebars.Utils.isEmpty(value);
+    return Handlebars.Utils.isEmpty(value, (Boolean) this.hash.getOrDefault("includeZero", false));
   }
 
   /**

tests/src/test/java/com/github/jknack/handlebars/jackson/Issue996.java

@@ -0,0 +1,41 @@
+/*
+ * Handlebars.java: https://github.com/jknack/handlebars.java
+ * Apache License Version 2.0 http://www.apache.org/licenses/LICENSE-2.0
+ * Copyright (c) 2012 Edgar Espina
+ */
+package com.github.jknack.handlebars.jackson;
+
+import java.io.IOException;
+
+import org.junit.jupiter.api.Test;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.github.jknack.handlebars.AbstractTest;
+import com.github.jknack.handlebars.Context;
+import com.github.jknack.handlebars.context.MapValueResolver;
+
+public class Issue996 extends AbstractTest {
+
+  @Override
+  protected Object configureContext(final Object model) {
+    return Context.newBuilder(model)
+        .resolver(MapValueResolver.INSTANCE, JsonNodeValueResolver.INSTANCE)
+        .build();
+  }
+
+  @Test
+  public void shouldSupportIncludeZeroOptionIfHelper() throws IOException {
+    JsonNode tree = new ObjectMapper().readTree("[1, 2, 3]");
+    shouldCompileTo(
+        "{{#if 0}}true condition{{else}}false condition{{/if}}", tree, "false condition");
+    shouldCompileTo(
+        "{{#if 0 includeZero=true}}true condition{{else}}false condition{{/if}}",
+        tree,
+        "true condition");
+    shouldCompileTo(
+        "{{#if 0 includeZero=false}}true condition{{else}}false condition{{/if}}",
+        tree,
+        "false condition");
+  }
+}