Introduce new.target C api (#3522)

Added new "jerry_get_new_target" API function
and updated the unit test.

JerryScript-DCO-1.0-Signed-off-by: Peter Gal pgal.u-szeged@partner.samsung.com

docs/02.API-REFERENCE.md

@@ -7655,6 +7655,138 @@ main (void)
 
 - [jerry_create_external_function](#jerry_create_external_function)
 
+## jerry_get_new_target
+
+**Summary**
+
+Returns the current "new.target" JavaScript function at the call site.
+
+If used outside of a native C function it will return "undefined" value.
+
+*Notes*:
+- Returned value must be freed with [jerry_release_value](#jerry_release_value) when it
+is no longer needed.
+- This feature depends on build option (`JERRY_ES2015`) and can be checked
+  in runtime with the `JERRY_FEATURE_SYMBOL` feature enum value (as symbols are enabled in case of ES2015),
+  see: [jerry_is_feature_enabled](#jerry_is_feature_enabled).
+- If the ES2015 mode is not enabled this method will always return the "undefined" value.
+
+**Prototype**
+
+```c
+jerry_value_t
+jerry_get_new_target (void);
+```
+- return
+  - "undefined" - if at the call site it was not a constructor call.
+  - function object - if the current call site is in a constructor call.
+
+*New in version 2.2*.
+
+**Example 1**
+
+[doctest]: # (name="02.API-REFERENCE-jsnewtarget-01.c")
+
+```c
+#include <stdio.h>
+#include <string.h>
+#include <jerryscript.h>
+
+static jerry_value_t
+demo_handler (const jerry_value_t func_obj_val,
+              const jerry_value_t this_val,
+              const jerry_value_t args_p[],
+              const jerry_length_t args_cnt)
+{
+  jerry_value_t new_target = jerry_get_new_target ();
+
+  /* new_target is the "demo" JS function object */
+  if (jerry_value_get_type (new_target) == JERRY_TYPE_FUNCTION)
+  {
+    printf ("This is a construct call\r\n");
+  }
+
+  jerry_release_value (new_target);
+
+  return jerry_create_undefined ();
+}
+
+int
+main (int argc, char** argv)
+{
+  jerry_init (JERRY_INIT_EMPTY);
+
+  jerry_value_t function_val = jerry_create_external_function (demo_handler);
+
+  jerry_value_t ret_val = jerry_construct_object (function_val, NULL, 0);
+
+  jerry_release_value (ret_val);
+  jerry_release_value (function_val);
+
+  jerry_cleanup ();
+  return 0;
+}
+```
+
+**Example 2**
+
+[doctest]: # (name="02.API-REFERENCE-jsnewtarget-02.c")
+
+```c
+#include <stdio.h>
+#include <string.h>
+#include <jerryscript.h>
+
+static jerry_value_t
+demo_handler (const jerry_value_t func_obj_val,
+              const jerry_value_t this_val,
+              const jerry_value_t args_p[],
+              const jerry_length_t args_cnt)
+{
+  jerry_value_t new_target = jerry_get_new_target ();
+
+  /* new_target is a JS function object */
+  if (jerry_value_get_type (new_target) == JERRY_TYPE_FUNCTION)
+  {
+    printf ("This is a construct call\r\n");
+  }
+
+  jerry_release_value (new_target);
+
+  return jerry_create_undefined ();
+}
+
+int
+main (int argc, char** argv)
+{
+  jerry_init (JERRY_INIT_EMPTY);
+
+  /* register C method */
+  jerry_value_t global_obj_val = jerry_get_global_object ();
+  jerry_value_t function_val = jerry_create_external_function (demo_handler);
+  jerry_value_t function_name_val = jerry_create_string ((const jerry_char_t *) "demo");
+  jerry_value_t result_val = jerry_set_property (global_obj_val, function_name_val, function_val);
+  jerry_release_value (result_val);
+  jerry_release_value (function_name_val);
+  jerry_release_value (function_val);
+  jerry_release_value (global_obj_val);
+
+  /* Invoke C method via JS */
+  const char *src = "new demo ()";
+  jerry_value_t ret_val = jerry_eval ((const jerry_char_t *) src,
+                                      strlen (src),
+                                      JERRY_PARSE_NO_OPTS);
+
+  jerry_release_value (ret_val);
+
+  jerry_cleanup ();
+  return 0;
+}
+```
+
+**See also**
+
+- [jerry_construct_object](#jerry_construct_object)
 
 # ArrayBuffer and TypedArray functions
 

jerry-core/api/jerry.c

@@ -3395,6 +3395,34 @@ jerry_get_resource_name (const jerry_value_t value) /**< jerry api value */
   return ecma_make_magic_string_value (LIT_MAGIC_STRING_RESOURCE_ANON);
 } /* jerry_get_resource_name */
 
+/**
+ * Access the "new.target" value.
+ *
+ * The "new.target" value depends on the current call site. That is
+ * this method will only have a function object result if, at the call site
+ * it was called inside a constructor method invoked with "new".
+ *
+ * @return "undefined" - if at the call site it was not a constructor call.
+ *         function object - if the current call site is in a constructor call.
+ */
+jerry_value_t
+jerry_get_new_target (void)
+{
+#if ENABLED (JERRY_ES2015)
+  ecma_object_t *current_new_target = JERRY_CONTEXT (current_new_target);
+
+  if (current_new_target == NULL || current_new_target == JERRY_CONTEXT_INVALID_NEW_TARGET)
+  {
+    return jerry_create_undefined ();
+  }
+
+  ecma_ref_object (current_new_target);
+  return ecma_make_object_value (current_new_target);
+#else /* !ENABLED (JERRY_ES2015) */
+  return jerry_create_undefined ();
+#endif /* ENABLED (JERRY_ES2015) */
+} /* jerry_get_new_target */
+
 /**
  * Check if the given value is an ArrayBuffer object.
  *

jerry-core/include/jerryscript-core.h

@@ -606,6 +606,7 @@ jerry_context_t *jerry_create_context (uint32_t heap_size, jerry_context_alloc_t
 void jerry_set_vm_exec_stop_callback (jerry_vm_exec_stop_callback_t stop_cb, void *user_p, uint32_t frequency);
 jerry_value_t jerry_get_backtrace (uint32_t max_depth);
 jerry_value_t jerry_get_resource_name (const jerry_value_t value);
+jerry_value_t jerry_get_new_target (void);
 
 /**
  * Array buffer components.

tests/unit-core/test-newtarget.c

@@ -46,16 +46,6 @@ enum
   TEST_ID_CONSTRUCT_AND_CALL_SUB = 3,
 };
 
-/**
- * Helper method to access the "new.target" via an eval call.
- */
-static jerry_value_t
-get_new_target (void)
-{
-  const char *src = "new.target";
-  return jerry_eval ((const jerry_char_t *) src, strlen (src), 0);
-} /* get_new_target */
-
 static jerry_value_t
 construct_handler (const jerry_value_t func_obj_val, /**< function object */
                    const jerry_value_t this_val, /**< this arg */
@@ -78,7 +68,7 @@ construct_handler (const jerry_value_t func_obj_val, /**< function object */
     case TEST_ID_SIMPLE_CONSTRUCT:
     {
       /* Method was called with "new": new.target should be equal to the function object. */
-      jerry_value_t target = get_new_target ();
+      jerry_value_t target = jerry_get_new_target ();
       TEST_ASSERT (!jerry_value_is_undefined (target));
       TEST_ASSERT (target == func_obj_val);
       jerry_release_value (target);
@@ -87,7 +77,7 @@ construct_handler (const jerry_value_t func_obj_val, /**< function object */
     case TEST_ID_SIMPLE_CALL:
     {
       /* Method was called directly without "new": new.target should be equal undefined. */
-      jerry_value_t target = get_new_target ();
+      jerry_value_t target = jerry_get_new_target ();
       TEST_ASSERT (jerry_value_is_undefined (target));
       TEST_ASSERT (target != func_obj_val);
       jerry_release_value (target);
@@ -96,7 +86,7 @@ construct_handler (const jerry_value_t func_obj_val, /**< function object */
     case TEST_ID_CONSTRUCT_AND_CALL_SUB:
     {
       /* Method was called with "new": new.target should be equal to the function object. */
-      jerry_value_t target = get_new_target ();
+      jerry_value_t target = jerry_get_new_target ();
       TEST_ASSERT (!jerry_value_is_undefined (target));
       TEST_ASSERT (target == func_obj_val);
       jerry_release_value (target);