[lldb/Lua] Make lldb.debugger et al available to Lua

The Python script interpreter makes the current debugger, target,
process, thread and frame available to interactive scripting sessions
through convenience variables. This patch does the same for Lua.

Differential revision: https://reviews.llvm.org/D71801

1 files changed, 34 insertions, 1 deletions

diff --git a/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.cpp b/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.cpp
index d5423b78b8c4..e46851c45092 100644
--- a/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.cpp
+++ b/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.cpp
@@ -27,7 +27,13 @@ public:
       : IOHandlerEditline(debugger, IOHandler::Type::LuaInterpreter, "lua",
                           ">>> ", "..> ", true, debugger.GetUseColor(), 0,
                           *this, nullptr),
-        m_script_interpreter(script_interpreter) {}
+        m_script_interpreter(script_interpreter) {
+    llvm::cantFail(m_script_interpreter.EnterSession(debugger.GetID()));
+  }
+
+  ~IOHandlerLuaInterpreter() {
+    llvm::cantFail(m_script_interpreter.LeaveSession());
+  }
 
   void IOHandlerInputComplete(IOHandler &io_handler,
                               std::string &data) override {
@@ -89,6 +95,33 @@ void ScriptInterpreterLua::Initialize() {
 
 void ScriptInterpreterLua::Terminate() {}
 
+llvm::Error ScriptInterpreterLua::EnterSession(user_id_t debugger_id) {
+  if (m_session_is_active)
+    return llvm::Error::success();
+
+  const char *fmt_str =
+      "lldb.debugger = lldb.SBDebugger.FindDebuggerWithID({0}); "
+      "lldb.target = lldb.debugger:GetSelectedTarget(); "
+      "lldb.process = lldb.target:GetProcess(); "
+      "lldb.thread = lldb.process:GetSelectedThread(); "
+      "lldb.frame = lldb.thread:GetSelectedFrame()";
+  return m_lua->Run(llvm::formatv(fmt_str, debugger_id).str());
+}
+
+llvm::Error ScriptInterpreterLua::LeaveSession() {
+  if (!m_session_is_active)
+    return llvm::Error::success();
+
+  m_session_is_active = false;
+
+  llvm::StringRef str = "lldb.debugger = nil; "
+                        "lldb.target = nil; "
+                        "lldb.process = nil; "
+                        "lldb.thread = nil; "
+                        "lldb.frame = nil";
+  return m_lua->Run(str);
+}
+
 lldb::ScriptInterpreterSP
 ScriptInterpreterLua::CreateInstance(Debugger &debugger) {
   return std::make_shared<ScriptInterpreterLua>(debugger);