[wip] Added undo operation for xeus-cpp

src/xinterpreter.cpp

@@ -133,14 +133,17 @@ __get_cxx_version ()
 
         auto input_guard = input_redirection(config.allow_stdin);
 
-        // Check for magics
-        for (auto& pre : preamble_manager.preamble)
+        if (code.find("%undo") != 0) 
         {
-            if (pre.second.is_match(code))
+            // Check for magics
+            for (auto& pre : preamble_manager.preamble)
             {
-                pre.second.apply(code, kernel_res);
-                cb(kernel_res);
-                return;
+                if (pre.second.is_match(code))
+                {
+                    pre.second.apply(code, kernel_res);
+                    cb(kernel_res);
+                    return;
+                }
             }
         }
 
@@ -168,7 +171,42 @@ __get_cxx_version ()
         try
         {
             StreamRedirectRAII R(err);
-            compilation_result = Cpp::Process(code.c_str());
+            if (code.rfind("%undo", 0) == 0)
+            {
+#ifdef EMSCRIPTEN
+                throw std::logic_error("Undo is not supported in xeus-cpp-lite");
+#else
+                int n = 1;  // Default value
+                if (code.length() > 5)
+                {
+                    try
+                    {
+                        n = std::stoi(code.substr(6));
+                    }
+                    catch (const std::invalid_argument&)
+                    {
+                        throw std::runtime_error(
+                            "Invalid format for %undo. Expected '%undo n' where n is an integer"
+                        );
+                    }
+                    catch (const std::out_of_range&)
+                    {
+                        throw std::runtime_error("Number out of range for %undo");
+                    }
+                }
+                compilation_result = static_cast<bool>(Cpp::Undo(n));
+#endif
+            }
+            else
+            {
+                compilation_result = Cpp::Process(code.c_str());
+            }
+        }
+        catch (std::logic_error& e)
+        {
+            errorlevel = 1;
+            ename = "Logic Error: ";
+            evalue = e.what();
         }
         catch (std::exception& e)
         {

test/test_interpreter.cpp

@@ -1076,3 +1076,78 @@ TEST_SUITE("file") {
         infile.close();
     }
 }
+
+
+TEST_SUITE("undo_and_redefinition")
+{
+#if defined(XEUS_CPP_EMSCRIPTEN_WASM_BUILD)
+    TEST_CASE("RedefinitionAndUndoErrors"
+            * doctest::should_fail(true)
+            * doctest::description("TODO: Currently fails for the Emscripten build"))
+#else
+    TEST_CASE("RedefinitionAndUndoErrors")
+#endif
+    {
+        std::vector<const char*> Args = {/*"-v", "resource-dir", "..."*/};
+        xcpp::interpreter interpreter((int) Args.size(), Args.data());
+        std::string code = R"(
+            int x = 5;
+        )";
+        nl::json user_expressions = nl::json::object();
+        xeus::execute_request_config config;
+        config.silent = false;
+        config.store_history = false;
+        config.allow_stdin = false;
+        nl::json header = nl::json::object();
+        xeus::xrequest_context::guid_list id = {};
+        xeus::xrequest_context context(header, id);
+
+        // Execute first code: define int x = 5
+        std::promise<nl::json> promise1;
+        std::future<nl::json> future1 = promise1.get_future();
+        auto callback1 = [&promise1](nl::json result)
+        {
+            promise1.set_value(result);
+        };
+        interpreter
+            .execute_request(std::move(context), std::move(callback1), code, std::move(config), user_expressions);
+        nl::json execute1 = future1.get();
+        REQUIRE(execute1["status"] == "ok");
+
+        code = R"(%undo)";
+        std::promise<nl::json> promise2;
+        std::future<nl::json> future2 = promise2.get_future();
+        auto callback2 = [&promise2](nl::json result)
+        {
+            promise2.set_value(result);
+        };
+        interpreter
+            .execute_request(std::move(context), std::move(callback2), code, std::move(config), user_expressions);
+        nl::json execute2 = future2.get();
+        REQUIRE(execute2["status"] == "ok");
+
+        code = "int x = 10;";
+        std::promise<nl::json> promise3;
+        std::future<nl::json> future3 = promise3.get_future();
+        auto callback3 = [&promise3](nl::json result)
+        {
+            promise3.set_value(result);
+        };
+        interpreter
+            .execute_request(std::move(context), std::move(callback3), code, std::move(config), user_expressions);
+        nl::json execute3 = future3.get();
+        REQUIRE(execute3["status"] == "ok");
+
+        code = "int x = 20;";
+        std::promise<nl::json> promise4;
+        std::future<nl::json> future4 = promise4.get_future();
+        auto callback4 = [&promise4](nl::json result)
+        {
+            promise4.set_value(result);
+        };
+        interpreter
+            .execute_request(std::move(context), std::move(callback4), code, std::move(config), user_expressions);
+        nl::json execute4 = future4.get();
+        REQUIRE(execute4["status"] == "error");
+    }
+}