LibJS: Make Array.prototype.push() generic

Author: https://github.com/linusg
Commit: 4334a1b208
Pull-request: https://github.com/SerenityOS/serenity/pull/2328

Libraries/LibJS/Runtime/ArrayPrototype.cpp

@@ -168,13 +168,30 @@ Value ArrayPrototype::map(Interpreter& interpreter)
 
 Value ArrayPrototype::push(Interpreter& interpreter)
 {
-    auto* array = array_from(interpreter);
+    auto* this_object = interpreter.this_value().to_object(interpreter);
-    if (!array)
+    if (!this_object)
         return {};
+    if (this_object->is_array()) {
+        auto* array = static_cast<Array*>(this_object);
         for (size_t i = 0; i < interpreter.argument_count(); ++i)
             array->elements().append(interpreter.argument(i));
         return Value(array->length());
     }
+    auto length = get_length(interpreter, *this_object);
+    if (interpreter.exception())
+        return {};
+    auto argument_count = interpreter.argument_count();
+    auto new_length = length + argument_count;
+    if (new_length > MAX_ARRAY_LIKE_INDEX)
+        return interpreter.throw_exception<TypeError>("Maximum array size exceeded");
+    for (size_t i = 0; i < argument_count; ++i)
+        this_object->put_by_index(length + i, interpreter.argument(i));
+    auto new_length_value = Value((i32)new_length);
+    this_object->put("length", new_length_value);
+    if (interpreter.exception())
+        return {};
+    return new_length_value;
+}
 
 Value ArrayPrototype::unshift(Interpreter& interpreter)
 {

Libraries/LibJS/Runtime/Value.cpp

@@ -43,9 +43,6 @@
 #include <LibJS/Runtime/Value.h>
 #include <math.h>
 
-// 2 ** 53 - 1
-#define MAX_ARRAY_LIKE_INDEX 9007199254740991.0
-
 namespace JS {
 
 bool Value::is_array() const
@@ -261,7 +258,7 @@ i32 Value::as_i32() const
 size_t Value::as_size_t() const
 {
     ASSERT(as_double() >= 0);
-    return min((double)(i32)as_double(), MAX_ARRAY_LIKE_INDEX);
+    return min((double)as_i32(), MAX_ARRAY_LIKE_INDEX);
 }
 
 double Value::to_double(Interpreter& interpreter) const

Libraries/LibJS/Runtime/Value.h

@@ -32,6 +32,9 @@
 #include <LibJS/Forward.h>
 #include <LibJS/Runtime/Symbol.h>
 
+// 2 ** 53 - 1
+static constexpr double MAX_ARRAY_LIKE_INDEX = 9007199254740991.0;
+
 namespace JS {
 
 class Value {

Libraries/LibJS/Tests/Array.prototype-generic-functions.js

@@ -1,11 +1,24 @@
 load("test-common.js");
 
 try {
+    [undefined, "foo", -42, 0].forEach(length => {
+        const o = { length };
+
+        assert(Array.prototype.push.call(o, "foo") === 1);
+        assert(o.length === 1);
+        assert(o[0] === "foo");
+        assert(Array.prototype.push.call(o, "bar", "baz") === 3);
+        assert(o.length === 3);
+        assert(o[0] === "foo");
+        assert(o[1] === "bar");
+        assert(o[2] === "baz");
+    });
+
     const o = { length: 5, 0: "foo", 1: "bar", 3: "baz" };
 
-    ["every"].forEach(name => {
+    {
         const visited = [];
-        Array.prototype[name].call(o, function (value) {
+        Array.prototype.every.call(o, function (value) {
             visited.push(value);
             return true;
         });
@@ -13,7 +26,7 @@ try {
         assert(visited[0] === "foo");
         assert(visited[1] === "bar");
         assert(visited[2] === "baz");
-    });
+    }
 
     ["find", "findIndex"].forEach(name => {
         const visited = [];