Add base implementation for returning callbacks in node port.

Author: viferga

source/ports/node_port/source/node_port.cpp

@@ -44,7 +44,9 @@ static void * metacall_node_napi_to_value(/* loader_impl_node node_impl,*/ napi_
 
 static napi_value metacall_node_value_to_napi(/* loader_impl_node node_impl,*/ napi_env env, void * arg);
 
-static void * metacall_node_callback(size_t argc, void * args[], void * data);
+static void * metacall_node_callback_value_to_napi(size_t argc, void * args[], void * data);
+
+static napi_value metacall_node_callback_napi_to_value(napi_env env, napi_callback_info info);
 
 typedef struct metacall_node_callback_closure_type
 {
@@ -58,7 +60,7 @@ typedef struct metacall_node_callback_closure_type
 
 /* BEGIN-TODO: (Maybe) Implement this in the loader, then remove it from here */
 
-void * metacall_node_callback(size_t argc, void * args[], void * data)
+void * metacall_node_callback_value_to_napi(size_t argc, void * args[], void * data)
 {
 	metacall_node_callback_closure closure = static_cast<metacall_node_callback_closure>(data);
 	napi_value ret;
@@ -119,6 +121,38 @@ void * metacall_node_callback(size_t argc, void * args[], void * data)
 	return result;
 }
 
+napi_value metacall_node_callback_napi_to_value(napi_env env, napi_callback_info info)
+{
+	void * f = NULL;
+	size_t iterator, argc = 0;
+
+	napi_get_cb_info(env, info, &argc, NULL, NULL, NULL);
+
+	napi_value argv[argc];
+	void * args[argc];
+	napi_value recv;
+
+	napi_get_cb_info(env, info, &argc, argv, &recv, &f);
+
+	for (iterator = 0; iterator < argc; ++iterator)
+	{
+		args[iterator] = metacall_node_napi_to_value(env, recv, argv[iterator]);
+	}
+
+	void * ret = metacallfv(f, args);
+
+	for (iterator = 0; iterator < argc; ++iterator)
+	{
+		metacall_value_destroy(args[iterator]);
+	}
+
+	napi_value result = metacall_node_value_to_napi(env, ret);
+
+	metacall_value_destroy(ret);
+
+	return result;
+}
+
 /* END-TODO */
 
 /* BEGIN-TODO: Remove this, it is duplicated code copied from node loader */
@@ -423,7 +457,7 @@ void * metacall_node_napi_to_value(/*loader_impl_node node_impl,*/ napi_env env,
 	}
 	else if (valuetype == napi_function)
 	{
-		void * f = metacall_function("__metacall_node_callback__");
+		void * f = metacall_function("__metacall_node_callback_value_to_napi__");
 		metacall_node_callback_closure closure = static_cast<metacall_node_callback_closure>(malloc(sizeof(struct metacall_node_callback_closure_type)));
 		napi_value length;
 		uint32_t argc;
@@ -609,15 +643,11 @@ napi_value metacall_node_value_to_napi(/* loader_impl_node node_impl,*/ napi_env
 	}
 	else if (id == METACALL_FUNCTION)
 	{
-		/* TODO: Implement function to pass callbacks through the callback again */
-		/*
 		void * f = metacall_value_to_function(arg_value);
 
-		// TODO:
-		status = napi_create_double(env, double_value, &v);
+		status = napi_create_function(env, NULL, 0, metacall_node_callback_napi_to_value, f, &v);
 
 		metacall_node_exception(env, status);
-		*/
 	}
 	else
 	{
@@ -863,7 +893,7 @@ napi_value metacall_node_initialize(napi_env env, napi_value exports)
 		return NULL;
 	}
 
-	if (metacall_register("__metacall_node_callback__", metacall_node_callback, METACALL_INVALID, 0) != 0)
+	if (metacall_register("__metacall_node_callback_value_to_napi__", metacall_node_callback_value_to_napi, METACALL_INVALID, 0) != 0)
 	{
 		/* TODO: Show error message (when error handling is properly implemented in the core lib) */
 		napi_throw_error(env, NULL, "MetaCall failed to initialize callback support");

source/ports/node_port/test/index.js

@@ -110,13 +110,23 @@ describe('metacall', () => {
 	describe('callback', () => {
 		it('callback (py)', () => {
 			const f = require('function.py');
-			const c = 5;
 			assert.notStrictEqual(f, undefined);
+
+			// Passing callback as an argument
+			const c = 5;
 			assert.strictEqual(f.function_with_args((a, b) => {
 				const result = a + b + c;
+				assert.strictEqual(a, 2);
+				assert.strictEqual(b, 3);
+				assert.strictEqual(c, 5);
 				console.log(`${a} + ${b} + ${c} = ${result}`);
 				return result;
 			}, 2, 3), 10);
+
+			// Passing callback as a return value
+			const callback = f.function_ret_lambda(10);
+			assert.notStrictEqual(callback, undefined);
+			assert.strictEqual(callback(3), 30);
 		});
 	});
 });

source/scripts/python/function/source/function.py

@@ -8,6 +8,10 @@ def function_with_args(cb, left, right):
 	print('Executing:', cb, '(', left, ',', right, ')');
 	return cb(left, right);
 
+def print_and_return(x):
+	print('Executing lambda with argument:', x);
+	return x;
+
 def function_ret_lambda(y):
 	print('Returning lambda with captured arg:', y);
-	return lambda x: x * y
+	return lambda x: print_and_return(x) * y