Implement Symbol.isConcatSpreadable (#3307)

Algorithm is based on ECMA-262 v6, 22.1.3.1.1

JerryScript-DCO-1.0-Signed-off-by: Adam Szilagyi aszilagy@inf.u-szeged.hu

jerry-core/ecma/base/ecma-helpers-value.c

@@ -405,6 +405,19 @@ ecma_check_value_type_is_spec_defined (ecma_value_t value) /**< ecma value */
                 || ecma_is_value_object (value));
 } /* ecma_check_value_type_is_spec_defined */
 
+/**
+ * Checks if the given argument is an array or not.
+ *
+ * @return true - if the given argument is an array object
+ *         false - otherwise
+ */
+inline bool JERRY_ATTR_CONST JERRY_ATTR_ALWAYS_INLINE
+ecma_is_value_array (ecma_value_t arg) /**< argument */
+{
+  return (ecma_is_value_object (arg)
+          && ecma_get_object_type (ecma_get_object_from_value (arg)) == ECMA_OBJECT_TYPE_ARRAY);
+} /* ecma_is_value_array */
+
 /**
  * Creates an ecma value from the given raw boolean.
  *

jerry-core/ecma/base/ecma-helpers.h

@@ -184,6 +184,7 @@ bool JERRY_ATTR_CONST ecma_is_value_direct_string (ecma_value_t value);
 bool JERRY_ATTR_CONST ecma_is_value_non_direct_string (ecma_value_t value);
 bool JERRY_ATTR_CONST ecma_is_value_object (ecma_value_t value);
 bool JERRY_ATTR_CONST ecma_is_value_error_reference (ecma_value_t value);
+bool JERRY_ATTR_CONST ecma_is_value_array (ecma_value_t arg);
 
 void ecma_check_value_type_is_spec_defined (ecma_value_t value);
 

jerry-core/ecma/builtin-objects/ecma-builtin-array.c

@@ -59,15 +59,7 @@ ecma_builtin_array_object_is_array (ecma_value_t this_arg, /**< 'this' argument
 {
   JERRY_UNUSED (this_arg);
 
-  if (ecma_is_value_object (arg))
-  {
-    if (ecma_get_object_type (ecma_get_object_from_value (arg)) == ECMA_OBJECT_TYPE_ARRAY)
-    {
-      return ECMA_VALUE_TRUE;
-    }
-  }
-
-  return ECMA_VALUE_FALSE;
+  return ecma_make_boolean_value (ecma_is_value_array (arg));
 } /* ecma_builtin_array_object_is_array */
 
 /**

jerry-core/ecma/builtin-objects/ecma-builtin-helpers.c

@@ -416,45 +416,64 @@ ecma_builtin_helper_array_concat_value (ecma_object_t *array_obj_p, /**< array *
                                         ecma_value_t value) /**< value to concat */
 {
   /* 5.b */
-  if (ecma_is_value_object (value))
+#if ENABLED (JERRY_ES2015)
+  ecma_value_t is_spreadable = ecma_op_is_concat_spreadable (value);
+
+  if (ECMA_IS_VALUE_ERROR (is_spreadable))
+  {
+    return is_spreadable;
+  }
+
+  bool spread_object = is_spreadable == ECMA_VALUE_TRUE;
+#else /* !ENABLED (JERRY_ES2015) */
+  bool spread_object = ecma_is_value_array (value);
+#endif /* ENABLED (JERRY_ES2015) */
+
+  if (spread_object)
   {
     ecma_object_t *obj_p = ecma_get_object_from_value (value);
 
-    if (ecma_get_object_type (obj_p) == ECMA_OBJECT_TYPE_ARRAY)
+#if ENABLED (JERRY_ES2015)
+    uint32_t arg_len;
+    ecma_value_t error = ecma_op_object_get_length (obj_p, &arg_len);
+
+    if (ECMA_IS_VALUE_ERROR (error))
     {
-      /* 5.b.ii */
-      uint32_t arg_len = ecma_array_get_length (obj_p);
+      return error;
+    }
+#else /* !ENABLED (JERRY_ES2015) */
+    /* 5.b.ii */
+    uint32_t arg_len = ecma_array_get_length (obj_p);
+#endif /* ENABLED (JERRY_ES2015) */
+    /* 5.b.iii */
+    for (uint32_t array_index = 0; array_index < arg_len; array_index++)
+    {
+      /* 5.b.iii.2 */
+      ecma_value_t get_value = ecma_op_object_find_by_uint32_index (obj_p, array_index);
 
-      /* 5.b.iii */
-      for (uint32_t array_index = 0; array_index < arg_len; array_index++)
+      if (ECMA_IS_VALUE_ERROR (get_value))
       {
-        /* 5.b.iii.2 */
-        ecma_value_t get_value = ecma_op_object_find_by_uint32_index (obj_p, array_index);
-
-        if (ECMA_IS_VALUE_ERROR (get_value))
-        {
-          return get_value;
-        }
-
-        if (!ecma_is_value_found (get_value))
-        {
-          continue;
-        }
-
-        /* 5.b.iii.3.b */
-        /* This will always be a simple value since 'is_throw' is false, so no need to free. */
-        ecma_value_t put_comp = ecma_builtin_helper_def_prop_by_index (array_obj_p,
-                                                                       *length_p + array_index,
-                                                                       get_value,
-                                                                       ECMA_PROPERTY_CONFIGURABLE_ENUMERABLE_WRITABLE);
-
-        JERRY_ASSERT (ecma_is_value_true (put_comp));
-        ecma_free_value (get_value);
+        return get_value;
       }
 
-      *length_p += arg_len;
-      return ECMA_VALUE_EMPTY;
+      if (!ecma_is_value_found (get_value))
+      {
+        continue;
+      }
+
+      /* 5.b.iii.3.b */
+      /* This will always be a simple value since 'is_throw' is false, so no need to free. */
+      ecma_value_t put_comp = ecma_builtin_helper_def_prop_by_index (array_obj_p,
+                                                                     *length_p + array_index,
+                                                                     get_value,
+                                                                     ECMA_PROPERTY_CONFIGURABLE_ENUMERABLE_WRITABLE);
+
+      JERRY_ASSERT (ecma_is_value_true (put_comp));
+      ecma_free_value (get_value);
     }
+
+    *length_p += arg_len;
+    return ECMA_VALUE_EMPTY;
   }
 
   /* 5.c.i */

jerry-core/ecma/operations/ecma-objects.c

@@ -19,6 +19,7 @@
 #include "ecma-exceptions.h"
 #include "ecma-gc.h"
 #include "ecma-globals.h"
+#include "ecma-helpers.h"
 #include "ecma-function-object.h"
 #include "ecma-lex-env.h"
 #include "ecma-string-object.h"
@@ -2474,6 +2475,43 @@ ecma_object_class_is (ecma_object_t *object_p, /**< object */
   return false;
 } /* ecma_object_class_is */
 
+#if ENABLED (JERRY_ES2015)
+/**
+ * Object's IsConcatSpreadable operation, used for Array.prototype.concat
+ * It checks the argument's [Symbol.isConcatSpreadable] property value
+ *
+ * See also:
+ *          ECMA-262 v6, 22.1.3.1.1;
+ *
+ * @return ECMA_VALUE_ERROR - if the operation fails
+ *         ECMA_VALUE_TRUE - if the argument is concatSpreadable
+ *         ECMA_VALUE_FALSE - otherwise
+ */
+ecma_value_t
+ecma_op_is_concat_spreadable (ecma_value_t arg) /**< argument */
+{
+  if (!ecma_is_value_object (arg))
+  {
+    return ECMA_VALUE_FALSE;
+  }
+
+  ecma_value_t spreadable = ecma_op_object_get_by_symbol_id (ecma_get_object_from_value (arg),
+                                                             LIT_MAGIC_STRING_IS_CONCAT_SPREADABLE);
+
+  if (ECMA_IS_VALUE_ERROR (spreadable))
+  {
+    return spreadable;
+  }
+
+  if (!ecma_is_value_undefined (spreadable))
+  {
+    return ecma_make_boolean_value (ecma_op_to_boolean (spreadable));
+  }
+
+  return (ecma_make_boolean_value (ecma_is_value_array (arg)));
+} /* ecma_op_is_concat_spreadable */
+#endif /* ENABLED (JERRY_ES2015) */
+
 /**
  * @}
  * @}

jerry-core/ecma/operations/ecma-objects.h

@@ -65,6 +65,9 @@ ecma_collection_t * ecma_op_object_get_property_names (ecma_object_t *obj_p, uin
 
 lit_magic_string_id_t ecma_object_get_class_name (ecma_object_t *obj_p);
 bool ecma_object_class_is (ecma_object_t *object_p, uint32_t class_id);
+#if ENABLED (JERRY_ES2015)
+ecma_value_t ecma_op_is_concat_spreadable (ecma_value_t arg);
+#endif /* ENABLED (JERRY_ES2015) */
 
 /**
  * @}

tests/jerry/es2015/symbol-isconcatspreadable.js

@@ -0,0 +1,81 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Test with regular arrays
+var alpha = ['a', 'b', 'c'];
+var numeric = [1, 2, 3];
+
+var alphaNumeric = alpha.concat(numeric);
+assert(JSON.stringify(alphaNumeric) === '["a","b","c",1,2,3]');
+assert(alphaNumeric.length === 6);
+
+numeric[Symbol.isConcatSpreadable] = false;
+alphaNumeric = alpha.concat(numeric);
+assert(JSON.stringify(alphaNumeric) === '["a","b","c",[1,2,3]]');
+assert(alphaNumeric.length === 4);
+
+numeric[Symbol.isConcatSpreadable] = true;
+
+// Test with array-like object
+var fakeArray = {
+  [Symbol.isConcatSpreadable]: true,
+  length: 2,
+  0: 4,
+  1: 5
+}
+
+var numericArray = numeric.concat(fakeArray);
+assert(JSON.stringify(numericArray) === '[1,2,3,4,5]');
+assert(numericArray.length === 5);
+
+fakeArray[Symbol.isConcatSpreadable] = false;
+numericArray = numeric.concat(fakeArray);
+assert(JSON.stringify(numericArray) === '[1,2,3,{"0":4,"1":5,"length":2}]');
+assert(numericArray.length === 4);
+
+// Test with object
+var obj = { 0: 'd' };
+
+var alphaObj = alpha.concat(obj);
+assert(JSON.stringify(alphaObj) === '["a","b","c",{"0":"d"}]');
+assert(alphaObj.length === 4);
+
+obj[Symbol.isConcatSpreadable] = true;
+alphaObj = alpha.concat(obj);
+assert(JSON.stringify(alphaObj) === '["a","b","c"]');
+assert(alphaObj.length === 3);
+
+// Test with boolean
+var bool = true;
+var numericBool = numeric.concat(bool);
+assert(JSON.stringify(numericBool) === '[1,2,3,true]');
+assert(numericBool.length === 4);
+
+bool[Symbol.isConcatSpreadable] = false;
+numericBool = numeric.concat(bool);
+assert(JSON.stringify(numericBool) === '[1,2,3,true]');
+assert(numericBool.length === 4);
+
+// Test when unable to concat
+var array1 = [];
+var array2 = [];
+Object.defineProperty(array2, '0', { 'get' : function () {throw new ReferenceError ("foo"); } });
+
+try {
+  array1.concat(array2);
+  assert(false);
+} catch (e) {
+  assert(e.message === "foo");
+  assert(e instanceof ReferenceError);
+}