LibJS: Implement 'in' operator

Author: https://github.com/linusg
Commit: https://github.com/SerenityOS/serenity/commit/11728b7db5e
Pull-request: https://github.com/SerenityOS/serenity/pull/1931
Reviewed-by: https://github.com/awesomekling

Libraries/LibJS/AST.cpp

@@ -331,6 +331,8 @@ Value BinaryExpression::execute(Interpreter& interpreter) const
         return right_shift(interpreter, lhs_result, rhs_result);
     case BinaryOp::UnsignedRightShift:
         return unsigned_right_shift(interpreter, lhs_result, rhs_result);
+    case BinaryOp::In:
+        return in(interpreter, lhs_result, rhs_result);
     case BinaryOp::InstanceOf:
         return instance_of(interpreter, lhs_result, rhs_result);
     }
@@ -512,6 +514,9 @@ void BinaryExpression::dump(int indent) const
     case BinaryOp::UnsignedRightShift:
         op_string = ">>>";
         break;
+    case BinaryOp::In:
+        op_string = "in";
+        break;
     case BinaryOp::InstanceOf:
         op_string = "instanceof";
         break;

Libraries/LibJS/AST.h

@@ -343,6 +343,7 @@ enum class BinaryOp {
     LeftShift,
     RightShift,
     UnsignedRightShift,
+    In,
     InstanceOf,
 };
 

Libraries/LibJS/Parser.cpp

@@ -566,6 +566,9 @@ NonnullRefPtr<Expression> Parser::parse_secondary_expression(NonnullRefPtr<Expre
     case TokenType::ExclamationMarkEquals:
         consume();
         return create_ast_node<BinaryExpression>(BinaryOp::AbstractInequals, move(lhs), parse_expression(min_precedence, associativity));
+    case TokenType::In:
+        consume();
+        return create_ast_node<BinaryExpression>(BinaryOp::In, move(lhs), parse_expression(min_precedence, associativity));
     case TokenType::Instanceof:
         consume();
         return create_ast_node<BinaryExpression>(BinaryOp::InstanceOf, move(lhs), parse_expression(min_precedence, associativity));
@@ -1076,6 +1079,7 @@ bool Parser::match_secondary_expression() const
         || type == TokenType::BracketOpen
         || type == TokenType::PlusPlus
         || type == TokenType::MinusMinus
+        || type == TokenType::In
         || type == TokenType::Instanceof
         || type == TokenType::QuestionMark
         || type == TokenType::Ampersand

Libraries/LibJS/Runtime/Value.cpp

@@ -382,6 +382,14 @@ Value eq(Interpreter& interpreter, Value lhs, Value rhs)
     return Value(false);
 }
 
+Value in(Interpreter& interpreter, Value lhs, Value rhs)
+{
+    if (!rhs.is_object())
+        return interpreter.throw_exception<TypeError>("'in' operator must be used on object");
+
+    return Value(rhs.as_object().get(lhs.to_string()).has_value());
+}
+
 Value instance_of(Interpreter&, Value lhs, Value rhs)
 {
     if (!lhs.is_object() || !rhs.is_object())

Libraries/LibJS/Runtime/Value.h

@@ -222,6 +222,7 @@ Value mod(Interpreter&, Value lhs, Value rhs);
 Value exp(Interpreter&, Value lhs, Value rhs);
 Value eq(Interpreter&, Value lhs, Value rhs);
 Value typed_eq(Interpreter&, Value lhs, Value rhs);
+Value in(Interpreter&, Value lhs, Value rhs);
 Value instance_of(Interpreter&, Value lhs, Value rhs);
 
 const LogStream& operator<<(const LogStream&, const Value&);

Libraries/LibJS/Tests/in-operator-basic.js

@@ -0,0 +1,35 @@
+load("test-common.js");
+
+try {
+    ["foo", 123, null, undefined].forEach(value => {
+        assertThrowsError(() => {
+            "prop" in value;
+        }, {
+            error: TypeError,
+            message: "'in' operator must be used on object"
+        });
+    });
+
+    var o = {foo: "bar", bar: undefined};
+    assert("" in o === false);
+    assert("foo" in o === true);
+    assert("bar" in o === true);
+    assert("baz" in o === false);
+    assert("toString" in o === true);
+
+    var a = ["hello", "friends"];
+    assert(0 in a === true);
+    assert(1 in a === true);
+    assert(2 in a === false);
+    assert("0" in a === true);
+    assert("hello" in a === false);
+    assert("friends" in a === false);
+    assert("length" in a === true);
+
+    var s = new String("foo");
+    assert("length" in s);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}