From 11728b7db5e79756e5a212c7fe4a1acaf5657767 Mon Sep 17 00:00:00 2001
From: Linus Groh <mail@linusgroh.de>
Date: Thu, 23 Apr 2020 16:06:01 +0100
Subject: [PATCH] LibJS: Implement 'in' operator

---
 Libraries/LibJS/AST.cpp                    |  5 ++++
 Libraries/LibJS/AST.h                      |  1 +
 Libraries/LibJS/Parser.cpp                 |  4 +++
 Libraries/LibJS/Runtime/Value.cpp          |  8 +++++
 Libraries/LibJS/Runtime/Value.h            |  1 +
 Libraries/LibJS/Tests/in-operator-basic.js | 35 ++++++++++++++++++++++
 6 files changed, 54 insertions(+)
 create mode 100644 Libraries/LibJS/Tests/in-operator-basic.js

diff --git a/Libraries/LibJS/AST.cpp b/Libraries/LibJS/AST.cpp
index 1fc0b29bf0..82871129a9 100644
--- a/Libraries/LibJS/AST.cpp
+++ b/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;
diff --git a/Libraries/LibJS/AST.h b/Libraries/LibJS/AST.h
index 8005441c74..72bac15cf9 100644
--- a/Libraries/LibJS/AST.h
+++ b/Libraries/LibJS/AST.h
@@ -343,6 +343,7 @@ enum class BinaryOp {
     LeftShift,
     RightShift,
     UnsignedRightShift,
+    In,
     InstanceOf,
 };
 
diff --git a/Libraries/LibJS/Parser.cpp b/Libraries/LibJS/Parser.cpp
index c58a9a3f27..b9b6cf0025 100644
--- a/Libraries/LibJS/Parser.cpp
+++ b/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
diff --git a/Libraries/LibJS/Runtime/Value.cpp b/Libraries/LibJS/Runtime/Value.cpp
index 2540621c85..ddb74d6d37 100644
--- a/Libraries/LibJS/Runtime/Value.cpp
+++ b/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())
diff --git a/Libraries/LibJS/Runtime/Value.h b/Libraries/LibJS/Runtime/Value.h
index c05ca22cc2..df0bd23efb 100644
--- a/Libraries/LibJS/Runtime/Value.h
+++ b/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&);
diff --git a/Libraries/LibJS/Tests/in-operator-basic.js b/Libraries/LibJS/Tests/in-operator-basic.js
new file mode 100644
index 0000000000..0cc523e756
--- /dev/null
+++ b/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);
+}