[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

10 files changed, 89 insertions, 3 deletions

diff --git a/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.cpp b/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.cpp
index dc64139fa4e..1dd0a9eade0 100644
--- a/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.cpp
+++ b/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.cpp
@@ -10,9 +10,9 @@
 #include "llvm/Support/FormatVariadic.h"
 
 using namespace lldb_private;
+using namespace lldb;
 
 llvm::Error Lua::Run(llvm::StringRef buffer) {
-  std::lock_guard<std::mutex> lock(m_mutex);
   int error =
       luaL_loadbuffer(m_lua_state, buffer.data(), buffer.size(), "buffer") ||
       lua_pcall(m_lua_state, 0, 0, 0);
diff --git a/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.h b/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.h
index ed1d159590a..adc6c611843 100644
--- a/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.h
+++ b/lldb/source/Plugins/ScriptInterpreter/Lua/Lua.h
@@ -9,6 +9,7 @@
 #ifndef liblldb_Lua_h_
 #define liblldb_Lua_h_
 
+#include "lldb/lldb-types.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Error.h"
 
@@ -38,7 +39,6 @@ public:
   llvm::Error Run(llvm::StringRef buffer);
 
 private:
-  std::mutex m_mutex;
   lua_State *m_lua_state;
 };
 
diff --git a/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.cpp b/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.cpp
index d5423b78b8c..e46851c4509 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);
diff --git a/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.h b/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.h
index b34c7d0e821..550e1035567 100644
--- a/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.h
+++ b/lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.h
@@ -43,8 +43,12 @@ public:
 
   Lua &GetLua();
 
+  llvm::Error EnterSession(lldb::user_id_t debugger_id);
+  llvm::Error LeaveSession();
+
 private:
   std::unique_ptr<Lua> m_lua;
+  bool m_session_is_active = false;
 };
 
 } // namespace lldb_private
diff --git a/lldb/test/Shell/ScriptInterpreter/Lua/Inputs/independent_state.in b/lldb/test/Shell/ScriptInterpreter/Lua/Inputs/independent_state.in
new file mode 100644
index 00000000000..6e15a8ff663
--- /dev/null
+++ b/lldb/test/Shell/ScriptInterpreter/Lua/Inputs/independent_state.in
@@ -0,0 +1,6 @@
+script foobar = 40 + 7
+script print(foobar)
+script d = lldb.SBDebugger.Create()
+script d:HandleCommand("script foobar = 40 + 2")
+script print(foobar)
+script d:HandleCommand("script print(foobar)")
diff --git a/lldb/test/Shell/ScriptInterpreter/Lua/Inputs/nested_sessions.in b/lldb/test/Shell/ScriptInterpreter/Lua/Inputs/nested_sessions.in
new file mode 100644
index 00000000000..75c57e364ca
--- /dev/null
+++ b/lldb/test/Shell/ScriptInterpreter/Lua/Inputs/nested_sessions.in
@@ -0,0 +1,6 @@
+script
+print(lldb.target, lldb.debugger:GetSelectedTarget())
+lldb.debugger:SetSelectedTarget(lldb.debugger:GetTargetAtIndex(0))
+print(lldb.target, lldb.debugger:GetSelectedTarget())
+lldb.debugger:HandleCommand("script print(lldb.target, lldb.debugger:GetSelectedTarget())")
+print(lldb.target, lldb.debugger:GetSelectedTarget())
diff --git a/lldb/test/Shell/ScriptInterpreter/Lua/Inputs/nested_sessions_2.in b/lldb/test/Shell/ScriptInterpreter/Lua/Inputs/nested_sessions_2.in
new file mode 100644
index 00000000000..a8cc2a57a55
--- /dev/null
+++ b/lldb/test/Shell/ScriptInterpreter/Lua/Inputs/nested_sessions_2.in
@@ -0,0 +1,2 @@
+script
+print(lldb.target, lldb.debugger:GetSelectedTarget())
diff --git a/lldb/test/Shell/ScriptInterpreter/Lua/convenience_variables.test b/lldb/test/Shell/ScriptInterpreter/Lua/convenience_variables.test
new file mode 100644
index 00000000000..022f2e38db4
--- /dev/null
+++ b/lldb/test/Shell/ScriptInterpreter/Lua/convenience_variables.test
@@ -0,0 +1,17 @@
+# REQUIRES: lua
+#
+# This tests that the convenience variables are not nil. Given that there is no
+# target we only expect the debugger to be valid.
+#
+# RUN: cat %s | %lldb --script-language lua 2>&1 | FileCheck %s
+script
+print(string.format("lldb.debugger is valid: %s", lldb.debugger:IsValid()))
+print(string.format("lldb.target is valid: %s", lldb.target:IsValid()))
+print(string.format("lldb.process is valid: %s", lldb.process:IsValid()))
+print(string.format("lldb.thread is valid: %s", lldb.thread:IsValid()))
+print(string.format("lldb.frame is valid: %s", lldb.frame:IsValid()))
+# CHECK: debugger is valid: true
+# CHECK: target is valid: false
+# CHECK: process is valid: false
+# CHECK: thread is valid: false
+# CHECK: frame is valid: false
diff --git a/lldb/test/Shell/ScriptInterpreter/Lua/independent_state.test b/lldb/test/Shell/ScriptInterpreter/Lua/independent_state.test
new file mode 100644
index 00000000000..2ade1b91c1c
--- /dev/null
+++ b/lldb/test/Shell/ScriptInterpreter/Lua/independent_state.test
@@ -0,0 +1,6 @@
+# REQUIRES: lua
+#
+# RUN:  %lldb --script-language lua -s %S/Inputs/independent_state.in 2>&1 | FileCheck %s
+# CHECK: 47
+# CHECK: 47
+# CHECK: 42
diff --git a/lldb/test/Shell/ScriptInterpreter/Lua/nested_sessions.test b/lldb/test/Shell/ScriptInterpreter/Lua/nested_sessions.test
new file mode 100644
index 00000000000..a81418b6af6
--- /dev/null
+++ b/lldb/test/Shell/ScriptInterpreter/Lua/nested_sessions.test
@@ -0,0 +1,12 @@
+# REQUIRES: lua
+# RUN: mkdir -p %t
+# RUN: echo "int main() { return 0; }" | %clang_host -x c - -o %t/foo
+# RUN: echo "int main() { return 0; }" | %clang_host -x c - -o %t/bar
+# RUN:  %lldb --script-language lua -o "file %t/bar" -o "file %t/foo" -s %S/Inputs/nested_sessions.in  -s %S/Inputs/nested_sessions_2.in 2>&1 | FileCheck %s
+# CHECK: script
+# CHECK-NEXT: foo foo
+# CHECK-NEXT: foo bar
+# CHECK-NEXT: foo bar
+# CHECK-NEXT: foo bar
+# CHECK: script
+# CHECK-NEXT: bar bar