Feature: Web REPL using Emscripten

.gitignore

@@ -5,3 +5,4 @@
 ^default.prof*
 ^fuzz-*
 ^luau$
+/.vs

CLI/Repl.cpp

@@ -253,6 +253,41 @@ static void completeRepl(lua_State* L, const char* editBuffer, std::vector<std::
     completeIndexer(L, editBuffer, start, completions);
 }
 
+#ifdef LUAU_WEB_REPL
+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)
+    {
+        std::unique_ptr<lua_State, void (*)(lua_State*)> globalState(luaL_newstate(), lua_close);
+        lua_State* L = globalState.get();
+
+        setupState(L);
+
+        luaL_sandboxthread(L);
+
+        linenoise::SetCompletionCallback([L](const char* editBuffer, std::vector<std::string>& completions) {
+            completeRepl(L, editBuffer, completions);
+        });
+
+        std::string error = runCode(L, source);
+
+        if (error.length())
+        {
+            fprintf(stdout, "%s\n", error.c_str());
+        }
+    }
+}
+#endif
+
 static void runRepl()
 {
     std::unique_ptr<lua_State, void (*)(lua_State*)> globalState(luaL_newstate(), lua_close);
@@ -424,6 +459,7 @@ static int assertionHandler(const char* expr, const char* file, int line)
     return 1;
 }
 
+#ifndef LUAU_WEB_REPL
 int main(int argc, char** argv)
 {
     Luau::assertHandler() = assertionHandler;
@@ -515,3 +551,4 @@ int main(int argc, char** argv)
         return failed;
     }
 }
+#endif

CMakeLists.txt

@@ -6,28 +6,58 @@ endif()
 
 cmake_minimum_required(VERSION 3.0)
 project(Luau LANGUAGES CXX)
+set(CMAKE_CXX_STANDARD 17)
 
 option(LUAU_BUILD_CLI "Build CLI" ON)
+option(LUAU_BUILD_WEB_REPL "Build Web CLI" ON)
 option(LUAU_BUILD_TESTS "Build tests" ON)
 
 add_library(Luau.Ast STATIC)
 add_library(Luau.Compiler STATIC)
 add_library(Luau.Analysis STATIC)
 add_library(Luau.VM STATIC)
 
-if(LUAU_BUILD_CLI)
-    add_executable(Luau.Repl.CLI)
-    add_executable(Luau.Analyze.CLI)
+if(LUAU_BUILD_WEB_REPL AND EMSCRIPTEN)
+    # this is a hack, disable cli and tests since we're compiling using emscripten
+    set(LUAU_BUILD_CLI OFF)
+    set(LUAU_BUILD_TESTS OFF)
 
-    # This also adds target `name` on Linux/macOS and `name.exe` on Windows
-    set_target_properties(Luau.Repl.CLI PROPERTIES OUTPUT_NAME luau)
-    set_target_properties(Luau.Analyze.CLI PROPERTIES OUTPUT_NAME luau-analyze)
-endif()
+    add_definitions(-DLUAU_WEB_REPL)
+
+    # luau web repl
+    add_executable(Luau.Repl.Web)
 
-if(LUAU_BUILD_TESTS)
-    add_executable(Luau.UnitTest)
-    add_executable(Luau.Conformance)
+    # configuration below
+    target_compile_options(Luau.Repl.Web PRIVATE ${LUAU_OPTIONS})
+
+    target_include_directories(Luau.Repl.Web PRIVATE extern)
+    target_link_libraries(Luau.Repl.Web PRIVATE Luau.Compiler Luau.VM)
+
+    if(UNIX)
+        target_link_libraries(Luau.Repl.Web PRIVATE pthread)
+    endif()
+
+    # declare exported functions to emscripten
+    target_link_options(Luau.Repl.Web PRIVATE -sEXPORTED_FUNCTIONS=['_getExceptionFromPtr','_executeScript'] -sEXPORTED_RUNTIME_METHODS=['ccall','cwrap'] -sNO_DISABLE_EXCEPTION_CATCHING)
+
+    # custom output directory for webm + js file
+    set_target_properties(Luau.Repl.Web PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${CMAKE_SOURCE_DIR}/docs/assets/luau)
+else()
+    if(LUAU_BUILD_CLI)
+        add_executable(Luau.Repl.CLI)
+        add_executable(Luau.Analyze.CLI)
+
+        # This also adds target `name` on Linux/macOS and `name.exe` on Windows
+        set_target_properties(Luau.Repl.CLI PROPERTIES OUTPUT_NAME luau)
+        set_target_properties(Luau.Analyze.CLI PROPERTIES OUTPUT_NAME luau-analyze)
+    endif()
+
+    if(LUAU_BUILD_TESTS)
+        add_executable(Luau.UnitTest)
+        add_executable(Luau.Conformance)
+    endif()
 endif()
+
 include(Sources.cmake)
 
 target_compile_features(Luau.Ast PUBLIC cxx_std_17)
@@ -54,7 +84,8 @@ else()
     list(APPEND LUAU_OPTIONS -Wall) # All warnings
     list(APPEND LUAU_OPTIONS -Werror) # Warnings are errors
 
-    if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    # temporary hot fix (removes need for commenting out line above when compiling with Clang)
+    if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
         list(APPEND LUAU_OPTIONS -Wno-unused) # GCC considers variables declared/checked in if() as unused
     endif()
 endif()

Sources.cmake

@@ -160,6 +160,16 @@ if(TARGET Luau.Repl.CLI)
         CLI/Repl.cpp)
 endif()
 
+if (TARGET Luau.Repl.Web)
+    # Luau.Repl.Web Sources
+    target_sources(Luau.Repl.Web PRIVATE
+        CLI/FileUtils.h
+        CLI/FileUtils.cpp
+        CLI/Profiler.h
+        CLI/Profiler.cpp
+        CLI/Repl.cpp)
+endif()
+
 if(TARGET Luau.Analyze.CLI)
     # Luau.Analyze.CLI Sources
     target_sources(Luau.Analyze.CLI PRIVATE

docs/_data/navigation.yml

@@ -25,3 +25,5 @@ pages:
     url: /profile
   - title: Library
     url: /library
+  - title: Demo
+    url: /demo

docs/_includes/repl.html

@@ -0,0 +1,53 @@
+<form>
+    <div>
+        <label>Script:</label>
+        <br>
+        <textarea rows="10" cols="70" id="script">print("Hello World!")</textarea>
+        <br><br>
+        <button onclick="clearInput(); return false;">
+            Clear Input
+        </button>
+        <button onclick="executeScript(); return false;">
+            Run
+        </button>
+    </div>
+    <br><br>
+    <div>
+        <label>Output:</label>
+        <br>
+        <textarea readonly rows="10" cols="70" id="output"></textarea>
+        <br><br>
+        <button onclick="clearOutput(); return false;">
+            Clear Output
+        </button>
+    </div>
+</form>
+
+<script>
+    function output(text) {
+        document.getElementById("output").value += new Date().toLocaleTimeString() + ": " + text + "\n";
+    }
+
+    var Module = {
+        'print': function (msg) { output(msg) },
+        'printErr': function (err) { } // potentially unused?
+    };
+
+    function clearInput() {
+        document.getElementById("script").value = "";
+    }
+
+    function clearOutput() {
+        document.getElementById("output").value = "";
+    }
+
+    function executeScript() {
+        try {
+            Module.ccall('executeScript', null, ['string'], [document.getElementById("script").value]);
+        }
+        catch (e) {
+            output(Module.ccall('getExceptionFromPtr', 'string', ['number'], [e]).replace('stdin', '[ERROR]'));
+        }
+    }
+</script>
+<script async src="assets/luau/Luau.Repl.Web.js"></script>

docs/_pages/demo.md

@@ -0,0 +1,7 @@
+---
+permalink: /demo
+title: Demo
+toc: true
+---
+
+{% include repl.html %}