[lldb/Lua] Implement a Simple Lua Script Interpreter Prototype

This implements a very elementary Lua script interpreter. It supports
running a single command as well as running interactively. It uses
editline if available. It's still missing a bunch of stuff though. Some
things that I intentionally ingored for now are that I/O isn't properly
hooked up (so every print goes to stdout) and the non-editline support
which is not handling a bunch of corner cases. The latter is a matter of
reusing existing code in the Python interpreter.

Discussion on the mailing list:
http://lists.llvm.org/pipermail/lldb-dev/2019-December/015812.html

Differential revision: https://reviews.llvm.org/D71234

4 files changed, 120 insertions, 12 deletions

diff --git a/lldb/source/Plugins/ScriptInterpreter/Lua/CMakeLists.txt b/lldb/source/Plugins/ScriptInterpreter/Lua/CMakeLists.txt
index 51161638a3d..498bd978395 100644
--- a/lldb/source/Plugins/ScriptInterpreter/Lua/CMakeLists.txt
+++ b/lldb/source/Plugins/ScriptInterpreter/Lua/CMakeLists.txt
@@ -1,7 +1,11 @@
 add_lldb_library(lldbPluginScriptInterpreterLua PLUGIN
+  Lua.cpp
   ScriptInterpreterLua.cpp
 
   LINK_LIBS
     lldbCore
     lldbInterpreter
-  )
\ No newline at end of file
+  )
+
+target_include_directories(lldbPluginScriptInterpreterLua PUBLIC ${LUA_INCLUDE_DIR})
+target_link_libraries(lldbPluginScriptInterpreterLua INTERFACE ${LUA_LIBRARIES})
diff --git a/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.cpp b/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.cpp
new file mode 100644
index 00000000000..a908ef08673
--- /dev/null
+++ b/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.cpp
@@ -0,0 +1,27 @@
+//===-- Lua.cpp -----------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "Lua.h"
+#include "llvm/Support/FormatVariadic.h"
+
+using namespace lldb_private;
+
+llvm::Error Lua::Run(llvm::StringRef buffer) {
+  int error =
+      luaL_loadbuffer(m_lua_state, buffer.data(), buffer.size(), "buffer") ||
+      lua_pcall(m_lua_state, 0, 0, 0);
+  if (!error)
+    return llvm::Error::success();
+
+  llvm::Error e = llvm::make_error<llvm::StringError>(
+      llvm::formatv("{0}\n", lua_tostring(m_lua_state, -1)),
+      llvm::inconvertibleErrorCode());
+  // Pop error message from the stack.
+  lua_pop(m_lua_state, 1);
+  return e;
+}
diff --git a/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.h b/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.h
new file mode 100644
index 00000000000..50b7ade4dc4
--- /dev/null
+++ b/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.h
@@ -0,0 +1,39 @@
+//===-- ScriptInterpreterLua.h ----------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef liblldb_Lua_h_
+#define liblldb_Lua_h_
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Error.h"
+
+#include "lua.hpp"
+
+namespace lldb_private {
+
+class Lua {
+public:
+  Lua() : m_lua_state(luaL_newstate()) {
+    assert(m_lua_state);
+    luaL_openlibs(m_lua_state);
+  }
+
+  ~Lua() {
+    assert(m_lua_state);
+    luaL_openlibs(m_lua_state);
+  }
+
+  llvm::Error Run(llvm::StringRef buffer);
+
+private:
+  lua_State *m_lua_state;
+};
+
+} // namespace lldb_private
+
+#endif // liblldb_Lua_h_
diff --git a/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.cpp b/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.cpp
index 78aa91a6959..b3f1689909f 100644
--- a/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.cpp
+++ b/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.cpp
@@ -7,35 +7,73 @@
 //===----------------------------------------------------------------------===//
 
 #include "ScriptInterpreterLua.h"
+#include "Lua.h"
 #include "lldb/Core/Debugger.h"
 #include "lldb/Core/PluginManager.h"
 #include "lldb/Core/StreamFile.h"
+#include "lldb/Interpreter/CommandReturnObject.h"
 #include "lldb/Utility/Stream.h"
 #include "lldb/Utility/StringList.h"
-
-#include "llvm/Support/Threading.h"
-
-#include <mutex>
+#include "lldb/Utility/Timer.h"
 
 using namespace lldb;
 using namespace lldb_private;
 
+class IOHandlerLuaInterpreter : public IOHandlerDelegate,
+                                public IOHandlerEditline {
+public:
+  IOHandlerLuaInterpreter(Debugger &debugger)
+      : IOHandlerEditline(debugger, IOHandler::Type::LuaInterpreter, "lua",
+                          ">>> ", "..> ", true, debugger.GetUseColor(), 0,
+                          *this, nullptr),
+        m_lua() {}
+
+  void IOHandlerInputComplete(IOHandler &io_handler,
+                              std::string &data) override {
+    if (llvm::Error error = m_lua.Run(data)) {
+      *GetOutputStreamFileSP() << llvm::toString(std::move(error));
+    }
+  }
+
+private:
+  Lua m_lua;
+};
+
 ScriptInterpreterLua::ScriptInterpreterLua(Debugger &debugger)
     : ScriptInterpreter(debugger, eScriptLanguageLua) {}
 
 ScriptInterpreterLua::~ScriptInterpreterLua() {}
 
 bool ScriptInterpreterLua::ExecuteOneLine(llvm::StringRef command,
-                                          CommandReturnObject *,
-                                          const ExecuteScriptOptions &) {
-  m_debugger.GetErrorStream().PutCString(
-      "error: the lua script interpreter is not yet implemented.\n");
-  return false;
+                                          CommandReturnObject *result,
+                                          const ExecuteScriptOptions &options) {
+  Lua l;
+  if (llvm::Error e = l.Run(command)) {
+    result->AppendErrorWithFormatv(
+        "lua failed attempting to evaluate '{0}': {1}\n", command,
+        llvm::toString(std::move(e)));
+    return false;
+  }
+  return true;
 }
 
 void ScriptInterpreterLua::ExecuteInterpreterLoop() {
-  m_debugger.GetErrorStream().PutCString(
-      "error: the lua script interpreter is not yet implemented.\n");
+  static Timer::Category func_cat(LLVM_PRETTY_FUNCTION);
+  Timer scoped_timer(func_cat, LLVM_PRETTY_FUNCTION);
+
+  Debugger &debugger = m_debugger;
+
+  // At the moment, the only time the debugger does not have an input file
+  // handle is when this is called directly from lua, in which case it is
+  // both dangerous and unnecessary (not to mention confusing) to try to embed
+  // a running interpreter loop inside the already running lua interpreter
+  // loop, so we won't do it.
+
+  if (!debugger.GetInputFile().IsValid())
+    return;
+
+  IOHandlerSP io_handler_sp(new IOHandlerLuaInterpreter(debugger));
+  debugger.PushIOHandler(io_handler_sp);
 }
 
 void ScriptInterpreterLua::Initialize() {