Provide support for native modules with ES6 imports (#3090)

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai dbatyai@inf.u-szeged.hu

Author: dbatyai

docs/05.PORT-API.md

@@ -83,10 +83,14 @@ information.
 void jerry_port_print_char (char c);
 ```
 
-### ES2015 Module system helper functions
+### ES2015 Module system
 
-The module system requires two specific functions for opening and closing files.
-It also requires a platform specific way of normalizing file paths.
+The port API provides functions that can be used by the module system to open
+and close source files, and normalize file paths.
+The `jerry_port_get_native_module` port function can be used to provide native
+modules to the engine. This function will be called when an import/export
+statement is encountered with an unknown module specifier, which embedders can
+use to supply native module objects based on the module name argument.
 
 ```c
 /**
@@ -126,6 +130,25 @@ jerry_port_normalize_path (const char *in_path_p, /**< input file path */
   // write to out_buf_p the normalized path
   // return length of written path
 } /* jerry_port_normalize_path */
+
+/**
+ * Get the module object of a native module.
+ *
+ * Note:
+ *      This port function is called by jerry-core when ES2015_MODULE_SYSTEM
+ *      is enabled.
+ *
+ * @param name String value of the module specifier.
+ *
+ * @return Undefined, if 'name' is not a native module
+ *         jerry_value_t containing the module object, otherwise
+ */
+jerry_value_t
+jerry_port_get_native_module (jerry_value_t name) /**< module specifier */
+{
+  (void) name;
+  return jerry_create_undefined ();
+}
 ```
 
 ## Date

docs/15.MODULE-SYSTEM.md

@@ -2,6 +2,7 @@
 
 The module system allows users to write import and export statements in scripts, which can be used to separate the logic of the application into custom modules.
 The standard's relevant part can be found [here](https://www.ecma-international.org/ecma-262/6.0/#sec-modules).
+Embedders wishing to use native builtin modules with ES6 imports can use the [Port API](05.PORT-API.md#es2015-module-system) to do so.
 
 ## General
 

jerry-core/ecma/base/ecma-module.c

@@ -97,12 +97,13 @@ ecma_module_create_normalized_path (const uint8_t *char_p, /**< module specifier
 } /* ecma_module_create_normalized_path */
 
 /**
- * Checks if we already have a module request in the module list.
+ * Find a module with a specific identifier
  *
- * @return pointer to found or newly created module structure
+ * @return pointer to ecma_module_t, if found
+ *         NULL, otherwise
  */
 ecma_module_t *
-ecma_module_find_or_create_module (ecma_string_t * const path_p) /**< module path */
+ecma_module_find_module (ecma_string_t *const path_p) /**< module identifier */
 {
   ecma_module_t *current_p = JERRY_CONTEXT (ecma_modules_p);
   while (current_p != NULL)
@@ -114,16 +115,59 @@ ecma_module_find_or_create_module (ecma_string_t * const path_p) /**< module pat
     current_p = current_p->next_p;
   }
 
-  current_p = (ecma_module_t *) jmem_heap_alloc_block (sizeof (ecma_module_t));
-  memset (current_p, 0, sizeof (ecma_module_t));
-
-  ecma_ref_ecma_string (path_p);
-  current_p->path_p = path_p;
-  current_p->next_p = JERRY_CONTEXT (ecma_modules_p);
-  JERRY_CONTEXT (ecma_modules_p) = current_p;
   return current_p;
+} /* ecma_module_find_module */
+
+/**
+ * Create a new module
+ *
+ * @return pointer to created module
+ */
+static ecma_module_t *
+ecma_module_create_module (ecma_string_t *const path_p) /**< module identifier */
+{
+  ecma_module_t *module_p = (ecma_module_t *) jmem_heap_alloc_block (sizeof (ecma_module_t));
+  memset (module_p, 0, sizeof (ecma_module_t));
+
+  module_p->path_p = path_p;
+  module_p->next_p = JERRY_CONTEXT (ecma_modules_p);
+  JERRY_CONTEXT (ecma_modules_p) = module_p;
+  return module_p;
+} /* ecma_module_create_module */
+
+/**
+ * Checks if we already have a module request in the module list.
+ *
+ * @return pointer to found or newly created module structure
+ */
+ecma_module_t *
+ecma_module_find_or_create_module (ecma_string_t *const path_p) /**< module path */
+{
+  ecma_module_t *module_p = ecma_module_find_module (path_p);
+  if (module_p)
+  {
+    ecma_deref_ecma_string (path_p);
+    return module_p;
+  }
+
+  return ecma_module_create_module (path_p);
 } /* ecma_module_find_or_create_module */
 
+/**
+ * Create a new native module
+ *
+ * @return pointer to created module
+ */
+ecma_module_t *
+ecma_module_create_native_module (ecma_string_t *const path_p, /**< module identifier */
+                                  ecma_object_t *const namespace_p) /**< module namespace */
+{
+  ecma_module_t *module_p = ecma_module_create_module (path_p);
+  module_p->state = ECMA_MODULE_STATE_NATIVE;
+  module_p->namespace_object_p = namespace_p;
+  return module_p;
+} /* ecma_module_create_native_module */
+
 /**
  * Creates a module context.
  *
@@ -274,6 +318,30 @@ ecma_module_resolve_export (ecma_module_t * const module_p, /**< base module */
         continue;
       }
 
+      if (current_module_p->state == ECMA_MODULE_STATE_NATIVE)
+      {
+        ecma_object_t *object_p = current_module_p->namespace_object_p;
+        ecma_value_t prop_value = ecma_op_object_find_own (ecma_make_object_value (object_p),
+                                                           object_p,
+                                                           current_export_name_p);
+        if (ecma_is_value_found (prop_value))
+        {
+          found = true;
+          found_record.module_p = current_module_p;
+          found_record.name_p = current_export_name_p;
+          ecma_free_value (prop_value);
+        }
+
+        if (ecma_compare_ecma_string_to_magic_id (current_export_name_p, LIT_MAGIC_STRING_DEFAULT))
+        {
+          ret_value = ecma_raise_syntax_error (ECMA_ERR_MSG ("No default export in native module."));
+          break;
+        }
+
+        ecma_module_resolve_stack_pop (&stack_p);
+        continue;
+      }
+
       if (context_p->local_exports_p != NULL)
       {
         /* 15.2.1.16.3 / 4 */
@@ -645,25 +713,44 @@ ecma_module_connect_imports (void)
           return ecma_raise_syntax_error (ECMA_ERR_MSG ("Ambiguous import request."));
         }
 
-        result = ecma_module_evaluate (record.module_p);
-
-        if (ECMA_IS_VALUE_ERROR (result))
+        if (record.module_p->state == ECMA_MODULE_STATE_NATIVE)
         {
-          return result;
+          ecma_object_t *object_p = record.module_p->namespace_object_p;
+          ecma_value_t prop_value = ecma_op_object_find_own (ecma_make_object_value (object_p),
+                                                             object_p,
+                                                             record.name_p);
+          JERRY_ASSERT (ecma_is_value_found (prop_value));
+
+          ecma_op_create_mutable_binding (local_env_p, import_names_p->local_name_p, true /* is_deletable */);
+          ecma_op_set_mutable_binding (local_env_p,
+                                       import_names_p->local_name_p,
+                                       prop_value,
+                                       false /* is_strict */);
+
+          ecma_free_value (prop_value);
         }
+        else
+        {
+          result = ecma_module_evaluate (record.module_p);
 
-        ecma_object_t *ref_base_lex_env_p;
-        ecma_value_t prop_value = ecma_op_get_value_lex_env_base (record.module_p->scope_p,
-                                                                  &ref_base_lex_env_p,
-                                                                  record.name_p);
+          if (ECMA_IS_VALUE_ERROR (result))
+          {
+            return result;
+          }
 
-        ecma_op_create_mutable_binding (local_env_p, import_names_p->local_name_p, true /* is_deletable */);
-        ecma_op_set_mutable_binding (local_env_p,
-                                     import_names_p->local_name_p,
-                                     prop_value,
-                                     false /* is_strict */);
+          ecma_object_t *ref_base_lex_env_p;
+          ecma_value_t prop_value = ecma_op_get_value_lex_env_base (record.module_p->scope_p,
+                                                                    &ref_base_lex_env_p,
+                                                                    record.name_p);
+
+          ecma_op_create_mutable_binding (local_env_p, import_names_p->local_name_p, true /* is_deletable */);
+          ecma_op_set_mutable_binding (local_env_p,
+                                       import_names_p->local_name_p,
+                                       prop_value,
+                                       false /* is_strict */);
 
-        ecma_free_value (prop_value);
+          ecma_free_value (prop_value);
+        }
       }
 
       import_names_p = import_names_p->next_p;
@@ -873,6 +960,17 @@ static void
 ecma_module_release_module (ecma_module_t *module_p) /**< module */
 {
   ecma_deref_ecma_string (module_p->path_p);
+
+  if (module_p->namespace_object_p != NULL)
+  {
+    ecma_deref_object (module_p->namespace_object_p);
+  }
+
+  if (module_p->state == ECMA_MODULE_STATE_NATIVE)
+  {
+    goto finished;
+  }
+
   if (module_p->state >= ECMA_MODULE_STATE_PARSING)
   {
     ecma_module_release_module_context (module_p->context_p);
@@ -889,11 +987,7 @@ ecma_module_release_module (ecma_module_t *module_p) /**< module */
     ecma_bytecode_deref (module_p->compiled_code_p);
   }
 
-  if (module_p->namespace_object_p != NULL)
-  {
-    ecma_deref_object (module_p->namespace_object_p);
-  }
-
+finished:
   jmem_heap_free_block (module_p, sizeof (ecma_module_t));
 } /* ecma_module_release_module */
 

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

@@ -70,6 +70,7 @@ typedef enum
   ECMA_MODULE_STATE_PARSED = 2,     /**< module has been parsed */
   ECMA_MODULE_STATE_EVALUATING = 3, /**< module is currently being evaluated */
   ECMA_MODULE_STATE_EVALUATED = 4,  /**< module has been evaluated */
+  ECMA_MODULE_STATE_NATIVE = 5,     /**< module is native */
 } ecma_module_state_t;
 
 /**
@@ -116,18 +117,21 @@ typedef struct ecma_module_resolve_stack
 } ecma_module_resolve_stack_t;
 
 bool ecma_module_resolve_set_insert (ecma_module_resolve_set_t **set_p,
-                                     ecma_module_t * const module_p,
-                                     ecma_string_t * const export_name_p);
+                                     ecma_module_t *const module_p,
+                                     ecma_string_t *const export_name_p);
 void ecma_module_resolve_set_cleanup (ecma_module_resolve_set_t *set_p);
 
 void ecma_module_resolve_stack_push (ecma_module_resolve_stack_t **stack_p,
-                                     ecma_module_t * const module_p,
-                                     ecma_string_t * const export_name_p);
+                                     ecma_module_t *const module_p,
+                                     ecma_string_t *const export_name_p);
 void ecma_module_resolve_stack_pop (ecma_module_resolve_stack_t **stack_p);
 
 ecma_string_t *ecma_module_create_normalized_path (const uint8_t *char_p,
                                                    prop_length_t size);
-ecma_module_t *ecma_module_find_or_create_module (ecma_string_t * const path_p);
+ecma_module_t *ecma_module_find_module (ecma_string_t *const path_p);
+ecma_module_t *ecma_module_create_native_module (ecma_string_t *const path_p,
+                                                 ecma_object_t *const namespace_p);
+ecma_module_t *ecma_module_find_or_create_module (ecma_string_t *const path_p);
 
 ecma_value_t ecma_module_connect_imports (void);
 ecma_value_t ecma_module_parse_modules (void);

jerry-core/include/jerryscript-port.h

@@ -21,6 +21,7 @@
 #include <stdio.h>
 
 #include "jerryscript-compiler.h"
+#include "jerryscript-core.h"
 
 #ifdef __cplusplus
 extern "C"
@@ -236,6 +237,20 @@ size_t jerry_port_normalize_path (const char *in_path_p,
                                   size_t out_buf_size,
                                   char *base_file_p);
 
+/**
+ * Get the module object of a native module.
+ *
+ * Note:
+ *      This port function is called by jerry-core when ES2015_MODULE_SYSTEM
+ *      is enabled.
+ *
+ * @param name String value of the module specifier.
+ *
+ * @return Undefined, if 'name' is not a native module
+ *         jerry_value_t containing the module object, otherwise
+ */
+jerry_value_t jerry_port_get_native_module (jerry_value_t name);
+
 /**
  * @}
  */

jerry-core/parser/js/js-parser-module.c

@@ -284,16 +284,12 @@ parser_module_context_init (void)
 
     if (path_p == NULL)
     {
+      ecma_ref_ecma_string (path_str_p);
       path_p = path_str_p;
     }
 
     ecma_module_t *module_p = ecma_module_find_or_create_module (path_p);
 
-    if (path_p != path_str_p)
-    {
-      ecma_deref_ecma_string (path_p);
-    }
-
     module_p->state = ECMA_MODULE_STATE_EVALUATED;
     module_p->scope_p = ecma_get_global_environment ();
     ecma_ref_object (module_p->scope_p);
@@ -542,6 +538,28 @@ parser_module_handle_module_specifier (parser_context_t *context_p) /**< parser
 
   lexer_construct_literal_object (context_p, &context_p->token.lit_location, LEXER_STRING_LITERAL);
 
+  ecma_string_t *name_p = ecma_new_ecma_string_from_utf8 (context_p->lit_object.literal_p->u.char_p,
+                                                          context_p->lit_object.literal_p->prop.length);
+
+  ecma_module_t *module_p = ecma_module_find_module (name_p);
+  if (module_p)
+  {
+    ecma_deref_ecma_string (name_p);
+    goto module_found;
+  }
+
+  ecma_value_t native = jerry_port_get_native_module (ecma_make_string_value (name_p));
+
+  if (!ecma_is_value_undefined (native))
+  {
+    JERRY_ASSERT (ecma_is_value_object (native));
+    ecma_object_t *module_object_p = ecma_get_object_from_value (native);
+
+    module_p = ecma_module_create_native_module (name_p, module_object_p);
+    goto module_found;
+  }
+
+  ecma_deref_ecma_string (name_p);
   ecma_string_t *path_p = ecma_module_create_normalized_path (context_p->lit_object.literal_p->u.char_p,
                                                               context_p->lit_object.literal_p->prop.length);
 
@@ -550,9 +568,9 @@ parser_module_handle_module_specifier (parser_context_t *context_p) /**< parser
     parser_raise_error (context_p, PARSER_ERR_FILE_NOT_FOUND);
   }
 
-  ecma_module_t *module_p = ecma_module_find_or_create_module (path_p);
-  ecma_deref_ecma_string (path_p);
+  module_p = ecma_module_find_or_create_module (path_p);
 
+module_found:
   module_node_p->module_request_p = module_p;
   lexer_next_token (context_p);
 } /* parser_module_handle_module_specifier */