From b90bf4cd52a547d1101426bf3af05ed8e50f27a5 Mon Sep 17 00:00:00 2001
From: Pelanyo Kamara <pkamara@disroot.org>
Date: Mon, 8 Nov 2021 19:06:47 +0000
Subject: [PATCH] add emscripten -fexceptions

---
 CLI/Repl.cpp             | 24 ++++++++++++------------
 CMakeLists.txt           |  5 ++++-
 docs/_includes/repl.html | 15 ++++++---------
 3 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/CLI/Repl.cpp b/CLI/Repl.cpp
index a0c74016..36159841 100644
--- a/CLI/Repl.cpp
+++ b/CLI/Repl.cpp
@@ -174,7 +174,7 @@ static std::string runCode(lua_State* L, const std::string& source)
     else
     {
         std::string error;
-
+        
         if (status == LUA_YIELD)
         {
             error = "thread yielded unexpectedly";
@@ -187,6 +187,11 @@ static std::string runCode(lua_State* L, const std::string& source)
         error += "\nstack backtrace:\n";
         error += lua_debugtrace(T);
 
+#ifdef __EMSCRIPTEN__
+        // nicer formatting for errors in web repl
+        error = "Error:" + error;
+#endif
+
         fprintf(stdout, "%s", error.c_str());
     }
 
@@ -197,16 +202,7 @@ static std::string runCode(lua_State* L, const std::string& source)
 #ifdef __EMSCRIPTEN__
 extern "C"
 {
-    // Luau errors are exceptions (see luaD_throw) which cannot be directly
-    // handled by emscripten. However we can recieve the pointer in JS and
-    // pass it through to this method to get the string content of the
-    // exception.
-    const char* getExceptionFromPtr(int ptr)
-    {
-        return reinterpret_cast<std::exception*>(ptr)->what();
-    }
-
-    void executeScript(const char* source)
+    const char* executeScript(const char* source)
     {
         // setup flags
         for (Luau::FValue<bool>* flag = Luau::FValue<bool>::list; flag; flag = flag->next)
@@ -220,14 +216,18 @@ extern "C"
         // setup state
         setupState(L);
 
+        // sandbox thread
+        luaL_sandboxthread(L);
+
         // run code + collect error
         std::string error = runCode(L, source);
 
         // output error(s)
         if (error.length())
         {
-            fprintf(stdout, "%s\n", error.c_str());
+            return std::move(error.c_str());
         }
+        return NULL;
     }
 }
 #endif
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 79c7ee31..36014a98 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -19,6 +19,9 @@ if(LUAU_BUILD_CLI)
     add_executable(Luau.Repl.CLI)
     if(NOT EMSCRIPTEN)
         add_executable(Luau.Analyze.CLI)
+    else()
+        # add -fexceptions for emscripten to allow exceptions to be caught in C++
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fexceptions")
     endif()
 
     # This also adds target `name` on Linux/macOS and `name.exe` on Windows
@@ -85,7 +88,7 @@ if(LUAU_BUILD_CLI)
 
     if(EMSCRIPTEN)
         # declare exported functions to emscripten
-        target_link_options(Luau.Repl.CLI PRIVATE -sEXPORTED_FUNCTIONS=['_getExceptionFromPtr','_executeScript'] -sEXPORTED_RUNTIME_METHODS=['ccall','cwrap'] -sNO_DISABLE_EXCEPTION_CATCHING)
+        target_link_options(Luau.Repl.CLI PRIVATE -sEXPORTED_FUNCTIONS=['_executeScript'] -sEXPORTED_RUNTIME_METHODS=['ccall','cwrap'] -fexceptions)
 
         # custom output directory for wasm + js file
         set_target_properties(Luau.Repl.CLI PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${CMAKE_SOURCE_DIR}/docs/assets/luau)
diff --git a/docs/_includes/repl.html b/docs/_includes/repl.html
index c2189a52..034dc5f7 100644
--- a/docs/_includes/repl.html
+++ b/docs/_includes/repl.html
@@ -25,12 +25,11 @@
 
 <script>
     function output(text) {
-        document.getElementById("output").value += new Date().toLocaleTimeString() + ": " + text + "\n";
+        document.getElementById("output").value += "[" + new Date().toLocaleTimeString() + "] " + text.replace('stdin:', '') + "\n";
     }
 
     var Module = {
-        'print': function (msg) { output(msg) },
-        'printErr': function (err) { } // potentially unused?
+        'print': function (msg) { output(msg) }
     };
 
     function clearInput() {
@@ -42,12 +41,10 @@
     }
 
     function executeScript() {
-        try {
-            Module.ccall('executeScript', null, ['string'], [document.getElementById("script").value]);
-        }
-        catch (e) {
-            output(Module.ccall('getExceptionFromPtr', 'string', ['number'], [e]).replace('stdin', '[ERROR]'));
+        var err = Module.ccall('executeScript', 'string', ['string'], [document.getElementById("script").value]);
+        if (err) {
+            output('Error:' + err.replace('stdin:', ''));
         }
     }
 </script>
-<script async src="assets/luau/Luau.Repl.Web.js"></script>
\ No newline at end of file
+<script async src="assets/luau/luau.js"></script>
\ No newline at end of file