Added undo command for CppInterOp (#513)

* added undo command for repl

* added undo command for repl

* added check for cling in CppInterOp.cpp

* added undo test for n > 1

* added unload feature for cling

* clang-format changes

* fixed c-api for undo

* test coverage

* test coverage

* test coverage

* skipped undo test for emscripten build

* skipped undo test for emscripten build

* using Cpp::Process ret val

* removed testing undo on first transac

* removed test for windows

---------

Co-authored-by: Abhinav Kumar <abhinavkumar@Abhinavs-MacBook-Air.local>

Author: kr-2003

include/clang/Interpreter/CppInterOp.h

@@ -785,6 +785,11 @@ namespace Cpp {
                                    unsigned complete_line = 1U,
                                    unsigned complete_column = 1U);
 
+  /// Reverts the last N operations performed by the interpreter.
+  ///\param[in] N The number of operations to undo. Defaults to 1.
+  ///\returns 0 on success, non-zero on failure.
+  CPPINTEROP_API int Undo(unsigned N = 1);
+
 } // end namespace Cpp
 
 #endif // CPPINTEROP_CPPINTEROP_H

lib/Interpreter/CXCppInterOp.cpp

@@ -306,7 +306,10 @@ TInterp_t clang_Interpreter_takeInterpreterAsPtr(CXInterpreter I) {
 
 enum CXErrorCode clang_Interpreter_undo(CXInterpreter I, unsigned int N) {
 #ifdef CPPINTEROP_USE_CLING
-  return CXError_Failure;
+  auto* interp = getInterpreter(I);
+  cling::Interpreter::PushTransactionRAII RAII(interp);
+  interp->unload(N);
+  return CXError_Success;
 #else
   return getInterpreter(I)->Undo(N) ? CXError_Failure : CXError_Success;
 #endif // CPPINTEROP_USE_CLING

lib/Interpreter/CppInterOp.cpp

@@ -3684,4 +3684,15 @@ namespace Cpp {
                          complete_column);
   }
 
+  int Undo(unsigned N) {
+#ifdef CPPINTEROP_USE_CLING
+    auto& I = getInterp();
+    cling::Interpreter::PushTransactionRAII RAII(&I);
+    I.unload(N);
+    return compat::Interpreter::kSuccess;
+#else
+    return getInterp().undo(N);
+#endif
+  }
+
   } // end namespace Cpp

lib/Interpreter/CppInterOpInterpreter.h

@@ -429,6 +429,15 @@ class Interpreter {
     return ret; // TODO: Implement
   }
 
+  CompilationResult undo(unsigned N = 1) {
+    if (llvm::Error Err = Undo(N)) {
+      llvm::logAllUnhandledErrors(std::move(Err), llvm::errs(),
+                                  "Failed to undo via ::undo");
+      return kFailure;
+    }
+    return kSuccess;
+  }
+
 }; // Interpreter
 } // namespace Cpp
 

unittests/CppInterOp/FunctionReflectionTest.cpp

@@ -1615,3 +1615,30 @@ TEST(FunctionReflectionTest, Destruct) {
   clang_Interpreter_takeInterpreterAsPtr(I);
   clang_Interpreter_dispose(I);
 }
+
+TEST(FunctionReflectionTest, UndoTest) {
+#ifdef _WIN32
+  GTEST_SKIP() << "Disabled on Windows. Needs fixing.";
+#endif
+#ifdef EMSCRIPTEN
+  GTEST_SKIP() << "Test fails for Emscipten builds";
+#else
+  Cpp::CreateInterpreter();
+  EXPECT_EQ(Cpp::Process("int a = 5;"), 0);
+  EXPECT_EQ(Cpp::Process("int b = 10;"), 0);
+  EXPECT_EQ(Cpp::Process("int x = 5;"), 0);
+  Cpp::Undo();
+  EXPECT_NE(Cpp::Process("int y = x;"), 0);
+  EXPECT_EQ(Cpp::Process("int x = 10;"), 0);
+  EXPECT_EQ(Cpp::Process("int y = 10;"), 0);
+  Cpp::Undo(2);
+  EXPECT_EQ(Cpp::Process("int x = 20;"), 0);
+  EXPECT_EQ(Cpp::Process("int y = 20;"), 0);
+  int ret = Cpp::Undo(100);
+#ifdef CPPINTEROP_USE_CLING
+  EXPECT_EQ(ret, 0);
+#else
+  EXPECT_EQ(ret, 1);
+#endif
+#endif
+  }