1 files changed, 269 insertions, 0 deletions
diff --git a/ext/pybind11/tests/test_embed/test_interpreter.cpp b/ext/pybind11/tests/test_embed/test_interpreter.cpp
new file mode 100644
index 000000000..6b5f051f2
--- /dev/null
+++ b/ext/pybind11/tests/test_embed/test_interpreter.cpp
@@ -0,0 +1,269 @@
+#include <pybind11/embed.h>
+#include <catch.hpp>
+
+#include <thread>
+#include <fstream>
+#include <functional>
+
+namespace py = pybind11;
+using namespace py::literals;
+
+class Widget {
+public:
+    Widget(std::string message) : message(message) { }
+    virtual ~Widget() = default;
+
+    std::string the_message() const { return message; }
+    virtual int the_answer() const = 0;
+
+private:
+    std::string message;
+};
+
+class PyWidget final : public Widget {
+    using Widget::Widget;
+
+    int the_answer() const override { PYBIND11_OVERLOAD_PURE(int, Widget, the_answer); }
+};
+
+PYBIND11_EMBEDDED_MODULE(widget_module, m) {
+    py::class_<Widget, PyWidget>(m, "Widget")
+        .def(py::init<std::string>())
+        .def_property_readonly("the_message", &Widget::the_message);
+
+    m.def("add", [](int i, int j) { return i + j; });
+}
+
+PYBIND11_EMBEDDED_MODULE(throw_exception, ) {
+    throw std::runtime_error("C++ Error");
+}
+
+PYBIND11_EMBEDDED_MODULE(throw_error_already_set, ) {
+    auto d = py::dict();
+    d["missing"].cast<py::object>();
+}
+
+TEST_CASE("Pass classes and data between modules defined in C++ and Python") {
+    auto module = py::module::import("test_interpreter");
+    REQUIRE(py::hasattr(module, "DerivedWidget"));
+
+    auto locals = py::dict("hello"_a="Hello, World!", "x"_a=5, **module.attr("__dict__"));
+    py::exec(R"(
+        widget = DerivedWidget("{} - {}".format(hello, x))
+        message = widget.the_message
+    )", py::globals(), locals);
+    REQUIRE(locals["message"].cast<std::string>() == "Hello, World! - 5");
+
+    auto py_widget = module.attr("DerivedWidget")("The question");
+    auto message = py_widget.attr("the_message");
+    REQUIRE(message.cast<std::string>() == "The question");
+
+    const auto &cpp_widget = py_widget.cast<const Widget &>();
+    REQUIRE(cpp_widget.the_answer() == 42);
+}
+
+TEST_CASE("Import error handling") {
+    REQUIRE_NOTHROW(py::module::import("widget_module"));
+    REQUIRE_THROWS_WITH(py::module::import("throw_exception"),
+                        "ImportError: C++ Error");
+    REQUIRE_THROWS_WITH(py::module::import("throw_error_already_set"),
+                        Catch::Contains("ImportError: KeyError"));
+}
+
+TEST_CASE("There can be only one interpreter") {
+    static_assert(std::is_move_constructible<py::scoped_interpreter>::value, "");
+    static_assert(!std::is_move_assignable<py::scoped_interpreter>::value, "");
+    static_assert(!std::is_copy_constructible<py::scoped_interpreter>::value, "");
+    static_assert(!std::is_copy_assignable<py::scoped_interpreter>::value, "");
+
+    REQUIRE_THROWS_WITH(py::initialize_interpreter(), "The interpreter is already running");
+    REQUIRE_THROWS_WITH(py::scoped_interpreter(), "The interpreter is already running");
+
+    py::finalize_interpreter();
+    REQUIRE_NOTHROW(py::scoped_interpreter());
+    {
+        auto pyi1 = py::scoped_interpreter();
+        auto pyi2 = std::move(pyi1);
+    }
+    py::initialize_interpreter();
+}
+
+bool has_pybind11_internals_builtin() {
+    auto builtins = py::handle(PyEval_GetBuiltins());
+    return builtins.contains(PYBIND11_INTERNALS_ID);
+};
+
+bool has_pybind11_internals_static() {
+    return py::detail::get_internals_ptr() != nullptr;
+}
+
+TEST_CASE("Restart the interpreter") {
+    // Verify pre-restart state.
+    REQUIRE(py::module::import("widget_module").attr("add")(1, 2).cast<int>() == 3);
+    REQUIRE(has_pybind11_internals_builtin());
+    REQUIRE(has_pybind11_internals_static());
+
+    // Restart the interpreter.
+    py::finalize_interpreter();
+    REQUIRE(Py_IsInitialized() == 0);
+
+    py::initialize_interpreter();
+    REQUIRE(Py_IsInitialized() == 1);
+
+    // Internals are deleted after a restart.
+    REQUIRE_FALSE(has_pybind11_internals_builtin());
+    REQUIRE_FALSE(has_pybind11_internals_static());
+    pybind11::detail::get_internals();
+    REQUIRE(has_pybind11_internals_builtin());
+    REQUIRE(has_pybind11_internals_static());
+
+    // Make sure that an interpreter with no get_internals() created until finalize still gets the
+    // internals destroyed
+    py::finalize_interpreter();
+    py::initialize_interpreter();
+    bool ran = false;
+    py::module::import("__main__").attr("internals_destroy_test") =
+        py::capsule(&ran, [](void *ran) { py::detail::get_internals(); *static_cast<bool *>(ran) = true; });
+    REQUIRE_FALSE(has_pybind11_internals_builtin());
+    REQUIRE_FALSE(has_pybind11_internals_static());
+    REQUIRE_FALSE(ran);
+    py::finalize_interpreter();
+    REQUIRE(ran);
+    py::initialize_interpreter();
+    REQUIRE_FALSE(has_pybind11_internals_builtin());
+    REQUIRE_FALSE(has_pybind11_internals_static());
+
+    // C++ modules can be reloaded.
+    auto cpp_module = py::module::import("widget_module");
+    REQUIRE(cpp_module.attr("add")(1, 2).cast<int>() == 3);
+
+    // C++ type information is reloaded and can be used in python modules.
+    auto py_module = py::module::import("test_interpreter");
+    auto py_widget = py_module.attr("DerivedWidget")("Hello after restart");
+    REQUIRE(py_widget.attr("the_message").cast<std::string>() == "Hello after restart");
+}
+
+TEST_CASE("Subinterpreter") {
+    // Add tags to the modules in the main interpreter and test the basics.
+    py::module::import("__main__").attr("main_tag") = "main interpreter";
+    {
+        auto m = py::module::import("widget_module");
+        m.attr("extension_module_tag") = "added to module in main interpreter";
+
+        REQUIRE(m.attr("add")(1, 2).cast<int>() == 3);
+    }
+    REQUIRE(has_pybind11_internals_builtin());
+    REQUIRE(has_pybind11_internals_static());
+
+    /// Create and switch to a subinterpreter.
+    auto main_tstate = PyThreadState_Get();
+    auto sub_tstate = Py_NewInterpreter();
+
+    // Subinterpreters get their own copy of builtins. detail::get_internals() still
+    // works by returning from the static variable, i.e. all interpreters share a single
+    // global pybind11::internals;
+    REQUIRE_FALSE(has_pybind11_internals_builtin());
+    REQUIRE(has_pybind11_internals_static());
+
+    // Modules tags should be gone.
+    REQUIRE_FALSE(py::hasattr(py::module::import("__main__"), "tag"));
+    {
+        auto m = py::module::import("widget_module");
+        REQUIRE_FALSE(py::hasattr(m, "extension_module_tag"));
+
+        // Function bindings should still work.
+        REQUIRE(m.attr("add")(1, 2).cast<int>() == 3);
+    }
+
+    // Restore main interpreter.
+    Py_EndInterpreter(sub_tstate);
+    PyThreadState_Swap(main_tstate);
+
+    REQUIRE(py::hasattr(py::module::import("__main__"), "main_tag"));
+    REQUIRE(py::hasattr(py::module::import("widget_module"), "extension_module_tag"));
+}
+
+TEST_CASE("Execution frame") {
+    // When the interpreter is embedded, there is no execution frame, but `py::exec`
+    // should still function by using reasonable globals: `__main__.__dict__`.
+    py::exec("var = dict(number=42)");
+    REQUIRE(py::globals()["var"]["number"].cast<int>() == 42);
+}
+
+TEST_CASE("Threads") {
+    // Restart interpreter to ensure threads are not initialized
+    py::finalize_interpreter();
+    py::initialize_interpreter();
+    REQUIRE_FALSE(has_pybind11_internals_static());
+
+    constexpr auto num_threads = 10;
+    auto locals = py::dict("count"_a=0);
+
+    {
+        py::gil_scoped_release gil_release{};
+        REQUIRE(has_pybind11_internals_static());
+
+        auto threads = std::vector<std::thread>();
+        for (auto i = 0; i < num_threads; ++i) {
+            threads.emplace_back([&]() {
+                py::gil_scoped_acquire gil{};
+                locals["count"] = locals["count"].cast<int>() + 1;
+            });
+        }
+
+        for (auto &thread : threads) {
+            thread.join();
+        }
+    }
+
+    REQUIRE(locals["count"].cast<int>() == num_threads);
+}
+
+// Scope exit utility https://stackoverflow.com/a/36644501/7255855
+struct scope_exit {
+    std::function<void()> f_;
+    explicit scope_exit(std::function<void()> f) noexcept : f_(std::move(f)) {}
+    ~scope_exit() { if (f_) f_(); }
+};
+
+TEST_CASE("Reload module from file") {
+    // Disable generation of cached bytecode (.pyc files) for this test, otherwise
+    // Python might pick up an old version from the cache instead of the new versions
+    // of the .py files generated below
+    auto sys = py::module::import("sys");
+    bool dont_write_bytecode = sys.attr("dont_write_bytecode").cast<bool>();
+    sys.attr("dont_write_bytecode") = true;
+    // Reset the value at scope exit
+    scope_exit reset_dont_write_bytecode([&]() {
+        sys.attr("dont_write_bytecode") = dont_write_bytecode;
+    });
+
+    std::string module_name = "test_module_reload";
+    std::string module_file = module_name + ".py";
+
+    // Create the module .py file
+    std::ofstream test_module(module_file);
+    test_module << "def test():\n";
+    test_module << "    return 1\n";
+    test_module.close();
+    // Delete the file at scope exit
+    scope_exit delete_module_file([&]() {
+        std::remove(module_file.c_str());
+    });
+
+    // Import the module from file
+    auto module = py::module::import(module_name.c_str());
+    int result = module.attr("test")().cast<int>();
+    REQUIRE(result == 1);
+
+    // Update the module .py file with a small change
+    test_module.open(module_file);
+    test_module << "def test():\n";
+    test_module << "    return 2\n";
+    test_module.close();
+
+    // Reload the module
+    module.reload();
+    result = module.attr("test")().cast<int>();
+    REQUIRE(result == 2);
+}