From b31cc0420e77d34465e4cf7d7ab75df7755b44d6 Mon Sep 17 00:00:00 2001
From: Benoit Giannangeli <benoit.giannangeli@boursorama.fr>
Date: Wed, 22 Feb 2017 13:54:30 +0100
Subject: assert

---
 README.md         |  2 +-
 src/lauxlib.js    |  4 +---
 src/lbaselib.js   | 13 +++++++++++++
 tests/lbaselib.js | 29 +++++++++++++++++++++++++++++
 4 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 75768b7..689d71c 100644
--- a/README.md
+++ b/README.md
@@ -215,7 +215,7 @@
         - [x] ipairs
         - [x] select
         - [x] tonumber
-        - [ ] assert
+        - [x] assert
         - [ ] next
         - [ ] pairs
         - [ ] rawlen
diff --git a/src/lauxlib.js b/src/lauxlib.js
index c44780e..e295fe6 100644
--- a/src/lauxlib.js
+++ b/src/lauxlib.js
@@ -12,9 +12,7 @@ const CT     = lua.constant_types;
 const LUA_LOADED_TABLE = "_LOADED"
 
 const panic = function(L) {
-    let msg = `PANIC: unprotected error in call to Lua API (${lapi.lua_tostring(L, -1)})`;
-    console.error(msg);
-    return 0;
+    throw new Error(`PANIC: unprotected error in call to Lua API (${lapi.lua_tostring(L, -1)})`);
 };
 
 // const luaL_argerror = function(L, arg, extramsg) {
diff --git a/src/lbaselib.js b/src/lbaselib.js
index 9cc4fb1..fa0349b 100644
--- a/src/lbaselib.js
+++ b/src/lbaselib.js
@@ -165,6 +165,18 @@ const luaB_error = function(L) {
     return lapi.lua_error(L);
 };
 
+const luaB_assert = function(L) {
+    if (lapi.lua_toboolean(L, 1))  /* condition is true? */
+        return lapi.lua_gettop(L);  /* return all arguments */
+    else {
+        lauxlib.luaL_checkany(L, 1);  /* there must be a condition */
+        lapi.lua_remove(L, 1);  /* remove it */
+        lapi.lua_pushliteral(L, "assertion failed!");  /* default message */
+        lapi.lua_settop(L, 1);  /* leave only message (default if no other one) */
+        return luaB_error(L);  /* call 'error' */
+    }
+};
+
 const luaB_select = function(L) {
     let n = lapi.lua_gettop(L);
     if (lapi.lua_type(L, 1) === CT.LUA_TSTRING && lapi.lua_tostring(L, 1) === "#") {
@@ -220,6 +232,7 @@ const luaB_xpcall = function(L) {
 
 const base_funcs = {
     "collectgarbage": function () {},
+    "assert":         luaB_assert,
     "print":          luaB_print,
     "tostring":       luaB_tostring,
     "tonumber":       luaB_tonumber,
diff --git a/tests/lbaselib.js b/tests/lbaselib.js
index 6dc6bfb..a7b14d9 100644
--- a/tests/lbaselib.js
+++ b/tests/lbaselib.js
@@ -489,4 +489,33 @@ test('tonumber', function (t) {
         2,
         "Correct element(s) on the stack"
     );
+});
+
+
+test('assert', function (t) {
+    let luaCode = `
+        assert(1 < 0, "this doesn't makes sense")
+    `, L;
+    
+    t.plan(2);
+
+    t.doesNotThrow(function () {
+
+        let bc = toByteCode(luaCode).dataView;
+
+        L = lauxlib.luaL_newstate();
+
+        linit.luaL_openlibs(L);
+
+        lapi.lua_load(L, bc, "test-assert");
+
+        lapi.lua_pcall(L, 0, -1, 0);
+
+    }, "JS Lua program ran without error");
+
+    t.ok(
+        lapi.lua_tostring(L, -1).endsWith("this doesn't makes sense"),
+        "Error is on the stack"
+    );
+
 });
\ No newline at end of file
-- 
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