Add notification callback for module state changes (#4656)

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

docs/02.API-REFERENCE.md

@@ -820,6 +820,32 @@ typedef jerry_value_t (*jerry_module_resolve_callback_t) (const jerry_value_t sp
 - [jerry_module_link](#jerry_module_link)
 - [jerry_get_global_object](#jerry_get_global_object)
 
+## jerry_module_state_changed_callback_t
+
+**Summary**
+
+Callback which is called after the module enters into linked, evaluated or error state.
+
+**Prototype**
+
+```c
+typedef void (*jerry_module_state_changed_callback_t) (jerry_module_state_t new_state,
+                                                       const jerry_value_t module,
+                                                       const jerry_value_t value,
+                                                       void *user_p);
+```
+
+- `new_state` - new state of the module.
+- `module` - a module whose state is changed
+- `value` - depends on the state: undefined for linked, module script result for evaluated,
+            and error value for error state.
+- `user_p` - pointer passed to [jerry_module_set_state_changed_callback](#jerry_module_set_state_changed_callback).
+
+*New in version [[NEXT_RELEASE]]*.
+
+**See also**
+- [jerry_module_set_state_changed_callback](#jerry_module_set_state_changed_callback)
+
 ## jerry_native_module_evaluate_callback_t
 
 **Summary**
@@ -4558,6 +4584,85 @@ main (void)
 
 - [jerry_module_state_t](#jerry_module_state_t)
 
+## jerry_module_set_state_changed_callback
+
+**Summary**
+
+Sets a callback which is called after a module state is changed to linked, evaluated, or error.
+
+*Notes*:
+- This API depends on a build option (`JERRY_MODULE_SYSTEM`) and can be checked
+  in runtime with the `JERRY_FEATURE_MODULE` feature enum value,
+  see: [jerry_is_feature_enabled](#jerry_is_feature_enabled).
+
+**Prototype**
+
+```c
+void
+jerry_module_set_state_changed_callback (jerry_module_state_changed_callback_t callback,
+                                         void *user_p)
+```
+
+- `callback` - callback, which is called after the state change.
+- `module_val` - pointer passed to the callback function.
+
+*New in version [[NEXT_RELEASE]]*.
+
+**Example**
+
+[doctest]: # (test="compile")
+
+```c
+#include <jerryscript.h>
+#include <stdio.h>
+
+static void
+module_state_changed (jerry_module_state_t new_state, /**< new state of the module */
+                      const jerry_value_t module_val, /**< a module whose state is changed */
+                      const jerry_value_t value, /**< value argument */
+                      void *user_p) /**< user pointer */
+{
+  (void) module_val;
+  (void) value;
+  (void) user_p;
+
+  if (new_state == JERRY_MODULE_STATE_LINKED)
+  {
+    printf ("A module is entered into linked state\n");
+  }
+} /* module_state_changed */
+
+int
+main (void)
+{
+  jerry_init (JERRY_INIT_EMPTY);
+
+  const jerry_char_t script[] = "12";
+  const jerry_char_t file[] = "a.mjs";
+
+  jerry_module_set_state_changed_callback (module_state_changed, NULL);
+
+  jerry_parse_options_t parse_options;
+  parse_options.options = JERRY_PARSE_MODULE | JERRY_PARSE_HAS_RESOURCE;
+  parse_options.resource_name_p = file;
+  parse_options.resource_name_length = sizeof (file) - 1;
+
+  jerry_value_t module_value = jerry_parse (script, sizeof (script) - 1, &parse_options);
+
+  jerry_release_value (jerry_module_link (module_value, NULL, NULL));
+
+  jerry_release_value (module_value);
+
+  jerry_cleanup ();
+  return 0;
+}
+```
+
+**See also**
+
+- [jerry_module_state_t](#jerry_module_state_t)
+- [jerry_module_state_changed_callback_t](#jerry_module_state_changed_callback_t)
+
 ## jerry_module_get_number_of_requests
 
 **Summary**