Adds jsonPath to error messages, so errors can be pinpointed.

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

@@ -57,7 +57,7 @@ public JsonLogic() {
   public JsonLogic addOperation(String name, Function<Object[], Object> function) {
     return addOperation(new PreEvaluatedArgumentsExpression() {
       @Override
-      public Object evaluate(List arguments, Object data) {
+      public Object evaluate(List arguments, Object data, String jsonPath) {
         return function.apply(arguments.toArray());
       }
 
@@ -84,7 +84,7 @@ public Object apply(String json, Object data) throws JsonLogicException {
       evaluator = new JsonLogicEvaluator(expressions);
     }
 
-    return evaluator.evaluate(parseCache.get(json), data);
+    return evaluator.evaluate(parseCache.get(json), data, "$");
   }
 
   public static boolean truthy(Object value) {

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

@@ -1,19 +1,24 @@
 package io.github.jamsesso.jsonlogic;
 
 public class JsonLogicException extends Exception {
+
+  private String jsonPath;
+
   private JsonLogicException() {
     // The default constructor should not be called for exceptions. A reason must be provided.
   }
 
-  public JsonLogicException(String msg) {
+  public JsonLogicException(String msg, String jsonPath) {
     super(msg);
+    this.jsonPath = jsonPath;
   }
 
-  public JsonLogicException(Throwable cause) {
+  public JsonLogicException(Throwable cause, String jsonPath) {
     super(cause);
+    this.jsonPath = jsonPath;
   }
 
-  public JsonLogicException(String msg, Throwable cause) {
-    super(msg, cause);
+  public String getJsonPath() {
+    return jsonPath;
   }
 }

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

@@ -3,15 +3,11 @@
 import io.github.jamsesso.jsonlogic.JsonLogicException;
 
 public class JsonLogicParseException extends JsonLogicException {
-  public JsonLogicParseException(String msg) {
-    super(msg);
+  public JsonLogicParseException(String msg, String jsonPath) {
+    super(msg, jsonPath);
   }
 
-  public JsonLogicParseException(Throwable cause) {
-    super(cause);
-  }
-
-  public JsonLogicParseException(String msg, Throwable cause) {
-    super(msg, cause);
+  public JsonLogicParseException(Throwable cause, String jsonPath) {
+    super(cause, jsonPath);
   }
 }

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

@@ -18,11 +18,14 @@ public static JsonLogicNode parse(String json) throws JsonLogicParseException {
       return parse(PARSER.parse(json));
     }
     catch (JsonSyntaxException e) {
-      throw new JsonLogicParseException(e);
+      throw new JsonLogicParseException(e, "$");
     }
   }
 
   private static JsonLogicNode parse(JsonElement root) throws JsonLogicParseException {
+    return parse(root, "$");
+  }
+  private static JsonLogicNode parse(JsonElement root, String jsonPath) throws JsonLogicParseException {
     // Handle null
     if (root.isJsonNull()) {
       return JsonLogicNull.NULL;
@@ -53,8 +56,9 @@ private static JsonLogicNode parse(JsonElement root) throws JsonLogicParseExcept
       JsonArray array = root.getAsJsonArray();
       List<JsonLogicNode> elements = new ArrayList<>(array.size());
 
+      int index = 0;
       for (JsonElement element : array) {
-        elements.add(parse(element));
+        elements.add(parse(element, String.format("%s[%d]", jsonPath, index++)));
       }
 
       return new JsonLogicArray(elements);
@@ -64,11 +68,11 @@ private static JsonLogicNode parse(JsonElement root) throws JsonLogicParseExcept
     JsonObject object = root.getAsJsonObject();
 
     if (object.keySet().size() != 1) {
-      throw new JsonLogicParseException("objects must have exactly 1 key defined, found " + object.keySet().size());
+      throw new JsonLogicParseException("objects must have exactly 1 key defined, found " + object.keySet().size(), jsonPath);
     }
 
     String key = object.keySet().stream().findAny().get();
-    JsonLogicNode argumentNode = parse(object.get(key));
+    JsonLogicNode argumentNode = parse(object.get(key), String.format("%s.%s", jsonPath, key));
     JsonLogicArray arguments;
 
     // Always coerce single-argument operations into a JsonLogicArray with a single element.

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

@@ -3,15 +3,11 @@
 import io.github.jamsesso.jsonlogic.JsonLogicException;
 
 public class JsonLogicEvaluationException extends JsonLogicException {
-  public JsonLogicEvaluationException(String msg) {
-    super(msg);
+  public JsonLogicEvaluationException(String msg, String jsonPath) {
+    super(msg, jsonPath);
   }
 
-  public JsonLogicEvaluationException(Throwable cause) {
-    super(cause);
-  }
-
-  public JsonLogicEvaluationException(String msg, Throwable cause) {
-    super(msg, cause);
+  public JsonLogicEvaluationException(Throwable cause, String jsonPath) {
+    super(cause, jsonPath);
   }
 }

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

@@ -20,12 +20,12 @@ public JsonLogicEvaluator(Map<String, JsonLogicExpression> expressions) {
     this.expressions = Collections.unmodifiableMap(expressions);
   }
 
-  public Object evaluate(JsonLogicNode node, Object data) throws JsonLogicEvaluationException {
+  public Object evaluate(JsonLogicNode node, Object data, String jsonPath) throws JsonLogicEvaluationException {
     switch (node.getType()) {
       case PRIMITIVE: return evaluate((JsonLogicPrimitive) node);
-      case VARIABLE: return evaluate((JsonLogicVariable) node, data);
-      case ARRAY: return evaluate((JsonLogicArray) node, data);
-      default: return evaluate((JsonLogicOperation) node, data);
+      case VARIABLE: return evaluate((JsonLogicVariable) node, data, jsonPath + ".var");
+      case ARRAY: return evaluate((JsonLogicArray) node, data, jsonPath);
+      default: return evaluate((JsonLogicOperation) node, data, jsonPath);
     }
   }
 
@@ -38,19 +38,20 @@ public Object evaluate(JsonLogicPrimitive<?> primitive) {
     }
   }
 
-  public Object evaluate(JsonLogicVariable variable, Object data) throws JsonLogicEvaluationException {
-    Object defaultValue = evaluate(variable.getDefaultValue(), null);
+  public Object evaluate(JsonLogicVariable variable, Object data, String jsonPath)
+      throws JsonLogicEvaluationException {
+    Object defaultValue = evaluate(variable.getDefaultValue(), null, jsonPath + "[1]");
 
     if (data == null) {
       return defaultValue;
     }
 
-    Object key = evaluate(variable.getKey(), data);
+    Object key = evaluate(variable.getKey(), data, jsonPath + "[0]");
 
     if (key == null) {
       return Optional.of(data)
         .map(JsonLogicEvaluator::transform)
-        .orElse(evaluate(variable.getDefaultValue(), null));
+        .orElse(evaluate(variable.getDefaultValue(), null, jsonPath + "[1]"));
     }
 
     if (key instanceof Number) {
@@ -78,21 +79,21 @@ public Object evaluate(JsonLogicVariable variable, Object data) throws JsonLogic
       String[] keys = name.split("\\.");
       Object result = data;
 
-      for(String partial : keys) {
-        result = evaluatePartialVariable(partial, result);
+      for (String partial : keys) {
+        result = evaluatePartialVariable(partial, result, jsonPath + "[0]");
 
-        if(result == null) {
+        if (result == null) {
           return defaultValue;
         }
       }
 
       return result;
     }
 
-    throw new JsonLogicEvaluationException("var first argument must be null, number, or string");
+    throw new JsonLogicEvaluationException("var first argument must be null, number, or string", jsonPath + "[0]");
   }
 
-  private Object evaluatePartialVariable(String key, Object data) throws JsonLogicEvaluationException {
+  private Object evaluatePartialVariable(String key, Object data, String jsonPath) throws JsonLogicEvaluationException {
     if (ArrayLike.isEligible(data)) {
       ArrayLike list = new ArrayLike(data);
       int index;
@@ -101,7 +102,7 @@ private Object evaluatePartialVariable(String key, Object data) throws JsonLogic
         index = Integer.parseInt(key);
       }
       catch (NumberFormatException e) {
-        throw new JsonLogicEvaluationException(e);
+        throw new JsonLogicEvaluationException(e, jsonPath);
       }
 
       if (index < 0 || index >= list.size()) {
@@ -118,24 +119,25 @@ private Object evaluatePartialVariable(String key, Object data) throws JsonLogic
     return null;
   }
 
-  public List<Object> evaluate(JsonLogicArray array, Object data) throws JsonLogicEvaluationException {
+  public List<Object> evaluate(JsonLogicArray array, Object data, String jsonPath) throws JsonLogicEvaluationException {
     List<Object> values = new ArrayList<>(array.size());
 
+    int index = 0;
     for(JsonLogicNode element : array) {
-      values.add(evaluate(element, data));
+      values.add(evaluate(element, data, String.format("%s[%d]", jsonPath, index++)));
     }
 
     return values;
   }
 
-  public Object evaluate(JsonLogicOperation operation, Object data) throws JsonLogicEvaluationException {
+  public Object evaluate(JsonLogicOperation operation, Object data, String jsonPath) throws JsonLogicEvaluationException {
     JsonLogicExpression handler = expressions.get(operation.getOperator());
 
     if (handler == null) {
-      throw new JsonLogicEvaluationException("Undefined operation '" + operation.getOperator() + "'");
+      throw new JsonLogicEvaluationException("Undefined operation '" + operation.getOperator() + "'", jsonPath);
     }
 
-    return handler.evaluate(this, operation.getArguments(), data);
+    return handler.evaluate(this, operation.getArguments(), data, String.format("%s.%s", jsonPath, operation.getOperator()));
   }
 
   public static Object transform(Object value) {
@@ -145,4 +147,4 @@ public static Object transform(Object value) {
 
     return value;
   }
-}
+}

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

@@ -5,6 +5,6 @@
 public interface JsonLogicExpression {
   String key();
 
-  Object evaluate(JsonLogicEvaluator evaluator, JsonLogicArray arguments, Object data)
+  Object evaluate(JsonLogicEvaluator evaluator, JsonLogicArray arguments, Object data, String jsonPath)
     throws JsonLogicEvaluationException;
 }

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

@@ -20,20 +20,20 @@ public String key() {
   }
 
   @Override
-  public Object evaluate(JsonLogicEvaluator evaluator, JsonLogicArray arguments, Object data)
+  public Object evaluate(JsonLogicEvaluator evaluator, JsonLogicArray arguments, Object data, String jsonPath)
     throws JsonLogicEvaluationException {
     if (arguments.size() != 2) {
-      throw new JsonLogicEvaluationException("all expects exactly 2 arguments");
+      throw new JsonLogicEvaluationException("all expects exactly 2 arguments", jsonPath);
     }
 
-    Object maybeArray = evaluator.evaluate(arguments.get(0), data);
+    Object maybeArray = evaluator.evaluate(arguments.get(0), data, jsonPath + "[0]");
 
     if (maybeArray == null) {
       return false;
     }
 
     if (!ArrayLike.isEligible(maybeArray)) {
-      throw new JsonLogicEvaluationException("first argument to all must be a valid array");
+      throw new JsonLogicEvaluationException("first argument to all must be a valid array", jsonPath);
     }
 
     ArrayLike array = new ArrayLike(maybeArray);
@@ -42,8 +42,9 @@ public Object evaluate(JsonLogicEvaluator evaluator, JsonLogicArray arguments, O
       return false;
     }
 
+    int index = 1;
     for (Object item : array) {
-      if(!JsonLogic.truthy(evaluator.evaluate(arguments.get(1), item))) {
+      if(!JsonLogic.truthy(evaluator.evaluate(arguments.get(1), item,  String.format("%s[%d]", jsonPath, index)))) {
         return false;
       }
     }

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

@@ -23,13 +23,13 @@ public String key() {
   }
 
   @Override
-  public Object evaluate(JsonLogicEvaluator evaluator, JsonLogicArray arguments, Object data)
+  public Object evaluate(JsonLogicEvaluator evaluator, JsonLogicArray arguments, Object data, String jsonPath)
     throws JsonLogicEvaluationException {
     if (arguments.size() != 2) {
-      throw new JsonLogicEvaluationException("some expects exactly 2 arguments");
+      throw new JsonLogicEvaluationException(key() + " expects exactly 2 arguments", jsonPath);
     }
 
-    Object maybeArray = evaluator.evaluate(arguments.get(0), data);
+    Object maybeArray = evaluator.evaluate(arguments.get(0), data, jsonPath + "[0]");
 
     // Array objects can have null values according to http://jsonlogic.com/
     if (maybeArray == null) {
@@ -41,15 +41,15 @@ public Object evaluate(JsonLogicEvaluator evaluator, JsonLogicArray arguments, O
     }
 
     if (!ArrayLike.isEligible(maybeArray)) {
-      throw new JsonLogicEvaluationException("first argument to some must be a valid array");
+      throw new JsonLogicEvaluationException("first argument to " + key() + " must be a valid array", jsonPath + "[0]");
     }
 
     for (Object item : new ArrayLike(maybeArray)) {
-      if(JsonLogic.truthy(evaluator.evaluate(arguments.get(1), item))) {
+      if(JsonLogic.truthy(evaluator.evaluate(arguments.get(1), item, jsonPath + "[1]"))) {
         return isSome;
       }
     }
 
     return !isSome;
   }
-}
+}

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

@@ -18,7 +18,7 @@ public String key() {
   }
 
   @Override
-  public Object evaluate(List arguments, Object data) throws JsonLogicEvaluationException {
+  public Object evaluate(List arguments, Object data, String jsonPath) throws JsonLogicEvaluationException {
     return arguments.stream()
       .map(obj -> {
         if (obj instanceof Double && obj.toString().endsWith(".0")) {

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

@@ -18,9 +18,9 @@ public String key() {
   }
 
   @Override
-  public Object evaluate(List arguments, Object data) throws JsonLogicEvaluationException {
+  public Object evaluate(List arguments, Object data, String jsonPath) throws JsonLogicEvaluationException {
     if (arguments.size() != 2) {
-      throw new JsonLogicEvaluationException("equality expressions expect exactly 2 arguments");
+      throw new JsonLogicEvaluationException("equality expressions expect exactly 2 arguments", jsonPath);
     }
 
     Object left = arguments.get(0);

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

@@ -23,22 +23,22 @@ public String key() {
   }
 
   @Override
-  public Object evaluate(JsonLogicEvaluator evaluator, JsonLogicArray arguments, Object data)
+  public Object evaluate(JsonLogicEvaluator evaluator, JsonLogicArray arguments, Object data, String jsonPath)
     throws JsonLogicEvaluationException {
     if (arguments.size() != 2) {
-      throw new JsonLogicEvaluationException("filter expects exactly 2 arguments");
+      throw new JsonLogicEvaluationException("filter expects exactly 2 arguments", jsonPath);
     }
 
-    Object maybeArray = evaluator.evaluate(arguments.get(0), data);
+    Object maybeArray = evaluator.evaluate(arguments.get(0), data, jsonPath + "[0]");
 
     if (!ArrayLike.isEligible(maybeArray)) {
-      throw new JsonLogicEvaluationException("first argument to filter must be a valid array");
+      throw new JsonLogicEvaluationException("first argument to filter must be a valid array", jsonPath + "[0]");
     }
 
     List<Object> result = new ArrayList<>();
 
     for (Object item : new ArrayLike(maybeArray)) {
-      if(JsonLogic.truthy(evaluator.evaluate(arguments.get(1), item))) {
+      if(JsonLogic.truthy(evaluator.evaluate(arguments.get(1), item, jsonPath + "[1]"))) {
         result.add(item);
       }
     }