Добавлен оператор объединения с null

src/main/java/com/annimon/ownlang/parser/Lexer.java

@@ -83,6 +83,7 @@ public final class Lexer {
         OPERATORS.put("**", TokenType.STARSTAR);
         OPERATORS.put("^^", TokenType.CARETCARET);
         OPERATORS.put("?:", TokenType.QUESTIONCOLON);
+        OPERATORS.put("??", TokenType.QUESTIONQUESTION);
     }
     
     private static final Map<String, TokenType> KEYWORDS;

src/main/java/com/annimon/ownlang/parser/Parser.java

@@ -473,7 +473,7 @@ public final class Parser {
     }
 
     private Expression ternary() {
-        Expression result = logicalOr();
+        Expression result = nullCoalesce();
 
         if (match(TokenType.QUESTION)) {
             final Expression trueExpr = expression();
@@ -487,6 +487,20 @@ public final class Parser {
         return result;
     }
 
+    private Expression nullCoalesce() {
+        Expression result = logicalOr();
+
+        while (true) {
+            if (match(TokenType.QUESTIONQUESTION)) {
+                result = new ConditionalExpression(ConditionalExpression.Operator.NULL_COALESCE, result, expression());
+                continue;
+            }
+            break;
+        }
+
+        return result;
+    }
+
     private Expression logicalOr() {
         Expression result = logicalAnd();
 

src/main/java/com/annimon/ownlang/parser/TokenType.java

@@ -69,6 +69,7 @@ public enum TokenType {
     DOTDOT, // ..
     STARSTAR, // **
     QUESTIONCOLON, // ?:
+    QUESTIONQUESTION, // ??
     
     TILDE, // ~
     CARET, // ^

src/main/java/com/annimon/ownlang/parser/ast/ConditionalExpression.java

@@ -21,7 +21,9 @@ public final class ConditionalExpression implements Expression {
         GTEQ(">="),
 
         AND("&&"),
-        OR("||");
+        OR("||"),
+
+        NULL_COALESCE("??");
 
         private final String name;
 
@@ -45,15 +47,22 @@ public final class ConditionalExpression implements Expression {
 
     @Override
     public Value eval() {
-        final Value value1 = expr1.eval();
         switch (operation) {
-            case AND: return NumberValue.fromBoolean(
-                    (value1.asInt() != 0) && (expr2.eval().asInt() != 0) );
-            case OR: return NumberValue.fromBoolean(
-                    (value1.asInt() != 0) || (expr2.eval().asInt() != 0) );
+            case AND:
+                return NumberValue.fromBoolean((expr1AsInt() != 0) && (expr2AsInt() != 0));
+            case OR:
+                return NumberValue.fromBoolean((expr1AsInt() != 0) || (expr2AsInt() != 0));
+
+            case NULL_COALESCE:
+                return nullCoalesce();
+
+            default:
+                return NumberValue.fromBoolean(evalAndCompare());
         }
+    }
 
-        
+    private boolean evalAndCompare() {
+        final Value value1 = expr1.eval();
         final Value value2 = expr2.eval();
 
         double number1, number2;
@@ -65,20 +74,39 @@ public final class ConditionalExpression implements Expression {
             number2 = 0;
         }
 
-        boolean result;
         switch (operation) {
-            case EQUALS: result = number1 == number2; break;
-            case NOT_EQUALS: result = number1 != number2; break;
+            case EQUALS: return number1 == number2;
+            case NOT_EQUALS: return number1 != number2;
 
-            case LT: result = number1 < number2; break;
-            case LTEQ: result = number1 <= number2; break;
-            case GT: result = number1 > number2; break;
-            case GTEQ: result = number1 >= number2; break;
+            case LT: return number1 < number2;
+            case LTEQ: return number1 <= number2;
+            case GT: return number1 > number2;
+            case GTEQ: return number1 >= number2;
 
             default:
                 throw new OperationIsNotSupportedException(operation);
         }
-        return NumberValue.fromBoolean(result);
+    }
+
+    private Value nullCoalesce() {
+        Value value1;
+        try {
+            value1 = expr1.eval();
+        } catch (NullPointerException npe) {
+            value1 = null;
+        }
+        if (value1 == null) {
+            return expr2.eval();
+        }
+        return value1;
+    }
+
+    private int expr1AsInt() {
+        return expr1.eval().asInt();
+    }
+
+    private int expr2AsInt() {
+        return expr2.eval().asInt();
     }
 
     @Override

src/test/resources/expressions/nullCoalesce.own

@@ -0,0 +1,27 @@
+def testZero() {
+  assertEquals(0, 0 ?? 1)
+  x = 0
+  assertEquals(0, x ?? 2)
+}
+
+def testObject() {
+  obj = {"a": 12}
+  assertEquals(12, obj.a ?? 10)
+}
+
+def testObjectMissingKey() {
+  obj = {"a": 12}
+  assertEquals(10, obj.test ?? 10)
+}
+
+def testNestedObjects() {
+  obj = {"a": {"b": 12}}
+  assertEquals(12, obj.a.b ?? 10)
+}
+
+def testNestedObjectsMissingKey() {
+  obj = {"a": {"b": 12}}
+  assertEquals(1, obj.test ?? 1)
+  assertEquals(2, obj.a.test ?? 2)
+  assertEquals(3, obj.test1.test2 ?? 3)
+}