Fixes bug arising from operating on empty arrays in '+' and '*' (#55)

Author: magnarn

src/main/java/io/github/jamsesso/jsonlogic/JsonLogicException.java

@@ -18,6 +18,11 @@ public JsonLogicException(Throwable cause, String jsonPath) {
     this.jsonPath = jsonPath;
   }
 
+  public JsonLogicException(String msg, Throwable cause, String jsonPath) {
+    super(msg, cause);
+    this.jsonPath = jsonPath;
+  }
+
   public String getJsonPath() {
     return jsonPath;
   }

src/main/java/io/github/jamsesso/jsonlogic/ast/JsonLogicParseException.java

@@ -10,4 +10,8 @@ public JsonLogicParseException(String msg, String jsonPath) {
   public JsonLogicParseException(Throwable cause, String jsonPath) {
     super(cause, jsonPath);
   }
+
+  public JsonLogicParseException(String msg, Throwable cause, String jsonPath) {
+    super(msg, cause, jsonPath);
+  }
 }

src/main/java/io/github/jamsesso/jsonlogic/evaluator/JsonLogicEvaluationException.java

@@ -10,4 +10,8 @@ public JsonLogicEvaluationException(String msg, String jsonPath) {
   public JsonLogicEvaluationException(Throwable cause, String jsonPath) {
     super(cause, jsonPath);
   }
+
+  public JsonLogicEvaluationException(String msg, Throwable cause, String jsonPath) {
+    super(msg, cause, jsonPath);
+  }
 }

src/main/java/io/github/jamsesso/jsonlogic/evaluator/expressions/MathExpression.java

@@ -48,7 +48,11 @@ public Object evaluate(List arguments, Object data, String jsonPath) throws Json
 
       if (key.equals("*") || key.equals("+")) {
         while (ArrayLike.isEligible(value)) {
-          value = new ArrayLike(value).get(0);
+          ArrayLike array = new ArrayLike(value);
+          if (array.isEmpty()) {
+            break;
+          }
+          value = array.get(0);
         }
       }
       if (value instanceof String) {

src/test/java/io/github/jamsesso/jsonlogic/MathExpressionTests.java

@@ -95,6 +95,14 @@ public void testMultiplyWithArray() throws JsonLogicException {
     assertEquals(6.0, result);  // This matches reference impl at jsonlogic.com
   }
 
+  @Test
+  public void testMultiplyWithEmptyArray() throws JsonLogicException {
+    String json = "{\"*\":[2,[]]}";
+    Object result = jsonLogic.apply(json, null);
+
+    assertEquals(null, result);  // This matches reference impl at jsonlogic.com
+  }
+
   @Test
   public void testDivide() throws JsonLogicException {
     String json = "{\"/\":[4,2]}";

src/test/resources/fixtures.json

@@ -931,6 +931,36 @@
     {},
     2
   ],
+  [
+    {
+      "+": [
+        1,
+        [2, 3]
+      ]
+    },
+    {},
+    3
+  ],
+  [
+    {
+      "+": [
+        1,
+        []
+      ]
+    },
+    {},
+    null
+  ],
+  [
+    {
+      "+": [
+        1,
+        null
+      ]
+    },
+    {},
+    null
+  ],
   [
     {
       "*": [
@@ -971,6 +1001,46 @@
     {},
     1
   ],
+  [
+    {
+      "*": [
+        [3, 4],
+        [2, 3]
+      ]
+    },
+    {},
+    6
+  ],
+  [
+    {
+      "*": [
+        3,
+        []
+      ]
+    },
+    {},
+    null
+  ],
+  [
+    {
+      "*": [
+        [],
+        []
+      ]
+    },
+    {},
+    null
+  ],
+  [
+    {
+      "*": [
+        3,
+        null
+      ]
+    },
+    {},
+    null
+  ],
   [
     {
       "-": [
@@ -3826,4 +3896,4 @@
     { "item": ["item4"] },
     false
   ]
-]
+]