[lldb/Lua] Support loading Lua modules

Implements the command script import command for Lua.

Differential revision: https://reviews.llvm.org/D71825

lldb/source/Plugins/ScriptInterpreter/Lua/Lua.cpp

@@ -7,6 +7,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "Lua.h"
+#include "lldb/Host/FileSystem.h"
+#include "lldb/Utility/FileSpec.h"
 #include "llvm/Support/FormatVariadic.h"
 
 using namespace lldb_private;
@@ -26,3 +28,32 @@ llvm::Error Lua::Run(llvm::StringRef buffer) {
   lua_pop(m_lua_state, 1);
   return e;
 }
+
+llvm::Error Lua::LoadModule(llvm::StringRef filename) {
+  FileSpec file(filename);
+  if (!FileSystem::Instance().Exists(file)) {
+    return llvm::make_error<llvm::StringError>("invalid path",
+                                               llvm::inconvertibleErrorCode());
+  }
+
+  ConstString module_extension = file.GetFileNameExtension();
+  if (module_extension != ".lua") {
+    return llvm::make_error<llvm::StringError>("invalid extension",
+                                               llvm::inconvertibleErrorCode());
+  }
+
+  int error = luaL_loadfile(m_lua_state, filename.data()) ||
+              lua_pcall(m_lua_state, 0, 1, 0);
+  if (error) {
+    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;
+  }
+
+  ConstString module_name = file.GetFileNameStrippingExtension();
+  lua_setglobal(m_lua_state, module_name.GetCString());
+  return llvm::Error::success();
+}

lldb/source/Plugins/ScriptInterpreter/Lua/Lua.h

@@ -37,6 +37,7 @@ public:
   }
 
   llvm::Error Run(llvm::StringRef buffer);
+  llvm::Error LoadModule(llvm::StringRef filename);
 
 private:
   lua_State *m_lua_state;

lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.cpp

@@ -83,6 +83,18 @@ void ScriptInterpreterLua::ExecuteInterpreterLoop() {
   debugger.PushIOHandler(io_handler_sp);
 }
 
+bool ScriptInterpreterLua::LoadScriptingModule(
+    const char *filename, bool init_session, lldb_private::Status &error,
+    StructuredData::ObjectSP *module_sp) {
+
+  if (llvm::Error e = m_lua->LoadModule(filename)) {
+    error.SetErrorStringWithFormatv("lua failed to import '{0}': {1}\n",
+                                    filename, llvm::toString(std::move(e)));
+    return false;
+  }
+  return true;
+}
+
 void ScriptInterpreterLua::Initialize() {
   static llvm::once_flag g_once_flag;
 

lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.h

@@ -25,6 +25,11 @@ public:
 
   void ExecuteInterpreterLoop() override;
 
+  virtual bool
+  LoadScriptingModule(const char *filename, bool init_session,
+                      lldb_private::Status &error,
+                      StructuredData::ObjectSP *module_sp = nullptr) override;
+
   // Static Functions
   static void Initialize();
 

lldb/test/Shell/ScriptInterpreter/Lua/Inputs/testmodule.lua

@@ -0,0 +1,7 @@
+local mymodule = {}
+
+function mymodule.foo()
+  print("Hello World!")
+end
+
+return mymodule

lldb/test/Shell/ScriptInterpreter/Lua/command_script_import.test

@@ -0,0 +1,13 @@
+# REQUIRES: lua
+# RUN: %lldb --script-language lua -o 'command script import %S/Inputs/testmodule.lua' -o 'script testmodule.foo()' 2>&1 | FileCheck %s
+# CHECK: Hello World!
+
+# RUN: mkdir -p %t
+# RUN: cp %S/Inputs/testmodule.lua %t/testmodule.notlua
+# RUN: %lldb --script-language lua -o 'command script import %t/testmodule.notlua' -o 'script testmodule.foo()' 2>&1 | FileCheck %s --check-prefix EXTENSION
+# EXTENSION: error: module importing failed: lua failed to import '{{.*}}testmodule.notlua': invalid extension
+# EXTENSION-NOT: Hello World!
+
+# RUN: %lldb --script-language lua -o 'command script import %S/Inputs/bogus' -o 'script testmodule.foo()' 2>&1 | FileCheck %s --check-prefix NONEXISTING
+# NONEXISTING: error: module importing failed: lua failed to import '{{.*}}bogus': invalid path
+# NONEXISTING-NOT: Hello World!