LibJS: Add spreading in object literals

Supports spreading strings, arrays, and other objects within object
literals.

4 files changed, 116 insertions, 0 deletions

diff --git a/Libraries/LibJS/AST.cpp b/Libraries/LibJS/AST.cpp
index d2e4ff039b..40bb117080 100644
--- a/Libraries/LibJS/AST.cpp
+++ b/Libraries/LibJS/AST.cpp
@@ -39,6 +39,7 @@
 #include <LibJS/Runtime/PrimitiveString.h>
 #include <LibJS/Runtime/Reference.h>
 #include <LibJS/Runtime/ScriptFunction.h>
+#include <LibJS/Runtime/Shape.h>
 #include <LibJS/Runtime/StringObject.h>
 #include <LibJS/Runtime/Value.h>
 #include <stdio.h>
@@ -1028,6 +1029,35 @@ Value ObjectExpression::execute(Interpreter& interpreter) const
         auto key_result = property.key().execute(interpreter);
         if (interpreter.exception())
             return {};
+
+        if (property.is_spread()) {
+            if (key_result.is_array()) {
+                auto& array_to_spread = static_cast<Array&>(key_result.as_object());
+                auto& elements = array_to_spread.elements();
+
+                for (size_t i = 0; i < elements.size(); ++i) {
+                    auto element = elements.at(i);
+                    if (!element.is_empty())
+                        object->put_by_index(i, element);
+                }
+            } else if (key_result.is_object()) {
+                auto& obj_to_spread = key_result.as_object();
+
+                for (auto& it : obj_to_spread.shape().property_table()) {
+                    if (obj_to_spread.has_own_property(it.key) && it.value.attributes & Attribute::Enumerable)
+                        object->put(it.key, obj_to_spread.get(it.key));
+                }
+            } else if (key_result.is_string()) {
+                auto& str_to_spread = key_result.as_string()->string();
+
+                for (size_t i = 0; i < str_to_spread.length(); i++) {
+                    object->put_by_index(i, js_string(interpreter, str_to_spread.substring(i, 1)));
+                }
+            }
+
+            continue;
+        }
+
         auto key = key_result.to_string();
         auto value = property.value().execute(interpreter);
         if (interpreter.exception())
diff --git a/Libraries/LibJS/AST.h b/Libraries/LibJS/AST.h
index 395367afec..27d660f99e 100644
--- a/Libraries/LibJS/AST.h
+++ b/Libraries/LibJS/AST.h
@@ -703,6 +703,9 @@ public:
     const Expression& key() const { return m_key; }
     const Expression& value() const { return m_value; }
 
+    bool is_spread() const { return m_is_spread; }
+    void set_is_spread() { m_is_spread = true; }
+
     virtual void dump(int indent) const override;
     virtual Value execute(Interpreter&) const override;
 
@@ -711,6 +714,7 @@ private:
 
     NonnullRefPtr<Expression> m_key;
     NonnullRefPtr<Expression> m_value;
+    bool m_is_spread { false };
 };
 
 class ObjectExpression : public Expression {
diff --git a/Libraries/LibJS/Parser.cpp b/Libraries/LibJS/Parser.cpp
index 63e0a5bd95..2288a31d92 100644
--- a/Libraries/LibJS/Parser.cpp
+++ b/Libraries/LibJS/Parser.cpp
@@ -446,6 +446,8 @@ NonnullRefPtr<ObjectExpression> Parser::parse_object_expression()
         RefPtr<Expression> property_key;
         RefPtr<Expression> property_value;
         auto need_colon = true;
+        auto is_spread = false;
+
         if (match_identifier_name()) {
             auto identifier = consume().value();
             property_key = create_ast_node<StringLiteral>(identifier);
@@ -459,6 +461,12 @@ NonnullRefPtr<ObjectExpression> Parser::parse_object_expression()
             consume(TokenType::BracketOpen);
             property_key = parse_expression(0);
             consume(TokenType::BracketClose);
+        } else if (match(TokenType::TripleDot)) {
+            consume(TokenType::TripleDot);
+            property_key = create_ast_node<SpreadExpression>(parse_expression(0));
+            property_value = property_key;
+            need_colon = false;
+            is_spread = true;
         } else {
             m_parser_state.m_has_errors = true;
             auto& current_token = m_parser_state.m_current_token;
@@ -476,6 +484,8 @@ NonnullRefPtr<ObjectExpression> Parser::parse_object_expression()
         }
         auto property = create_ast_node<ObjectProperty>(*property_key, *property_value);
         properties.append(property);
+        if (is_spread)
+            property->set_is_spread();
 
         if (!match(TokenType::Comma))
             break;
diff --git a/Libraries/LibJS/Tests/object-spread.js b/Libraries/LibJS/Tests/object-spread.js
new file mode 100644
index 0000000000..18fab7abb8
--- /dev/null
+++ b/Libraries/LibJS/Tests/object-spread.js
@@ -0,0 +1,72 @@
+load("test-common.js");
+
+function testObjSpread(obj) {
+    return obj.foo === 0 && 
+        obj.bar === 1 &&
+        obj.baz === 2 &&
+        obj.qux === 3;
+}
+
+function testObjStrSpread(obj) {
+    return obj[0] === "a" && 
+        obj[1] === "b" && 
+        obj[2] === "c" &&
+        obj[3] === "d";
+}
+
+try {
+    let obj = { 
+        foo: 0, 
+        ...{ bar: 1, baz: 2 }, 
+        qux: 3,
+    };
+    assert(testObjSpread(obj));
+
+    obj = { foo: 0, bar: 1, baz: 2 };
+    obj.qux = 3;
+    assert(testObjSpread({ ...obj }));
+
+    let a = { bar: 1, baz: 2 };
+    obj = { foo: 0, ...a, qux: 3 };
+    assert(testObjSpread(obj));
+
+    obj = {
+        ...{},
+        ...{
+            ...{ foo: 0, bar: 1, baz: 2 },
+        },
+        qux: 3,
+    };
+    assert(testObjSpread(obj));
+
+    obj = { ..."abcd" };
+    assert(testObjStrSpread(obj));
+    
+    obj = { ...["a", "b", "c", "d"] };
+    assert(testObjStrSpread(obj));
+    
+    obj = { ...String("abcd") };
+    assert(testObjStrSpread(obj));
+
+    a = { foo: 0 };
+    Object.defineProperty(a, 'bar', {
+        value: 1,
+        enumerable: false,
+    });
+    obj = { ...a };
+    assert(obj.foo === 0 && obj.bar === undefined);
+
+    let empty = ({
+        ...undefined,
+        ...null,
+        ...1,
+        ...true,
+        ...function(){},
+        ...Date,
+    });
+    assert(Object.getOwnPropertyNames(empty).length === 0);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}
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