possible bug with IntEnums and function arg default value stub rendering

[nurpax]

I define an enum like so:

nb::enum_<ImGuiInputTextFlags_>(m, "InputTextFlags", nb::is_arithmetic())
    .value("NONE", ImGuiInputTextFlags_None)
    .value("CHARS_DECIMAL", ImGuiInputTextFlags_CharsDecimal)
    .value("CHARS_HEXADECIMAL", ImGuiInputTextFlags_CharsHexadecimal)
    .value("CHARS_UPPERCASE", ImGuiInputTextFlags_CharsUppercase)
    .value("CHARS_NO_BLANK", ImGuiInputTextFlags_CharsNoBlank)
    .value("AUTO_SELECT_ALL", ImGuiInputTextFlags_AutoSelectAll)
    .value("ENTER_RETURNS_TRUE", ImGuiInputTextFlags_EnterReturnsTrue)
    .value("CALLBACK_COMPLETION", ImGuiInputTextFlags_CallbackCompletion)
    .value("CALLBACK_HISTORY", ImGuiInputTextFlags_CallbackHistory)
    .value("CALLBACK_ALWAYS", ImGuiInputTextFlags_CallbackAlways)
    .value("CALLBACK_CHAR_FILTER", ImGuiInputTextFlags_CallbackCharFilter)
    .value("ALLOW_TAB_INPUT", ImGuiInputTextFlags_AllowTabInput)
    .value("CTRL_ENTER_FOR_NEW_LINE", ImGuiInputTextFlags_CtrlEnterForNewLine)
    .value("NO_HORIZONTAL_SCROLL", ImGuiInputTextFlags_NoHorizontalScroll)
    .value("ALWAYS_OVERWRITE", ImGuiInputTextFlags_AlwaysOverwrite)
    .value("READ_ONLY", ImGuiInputTextFlags_ReadOnly)
    .value("PASSWORD", ImGuiInputTextFlags_Password)
    .value("NO_UNDO_REDO", ImGuiInputTextFlags_NoUndoRedo)
    .value("CHARS_SCIENTIFIC", ImGuiInputTextFlags_CharsScientific)
    .value("CALLBACK_RESIZE", ImGuiInputTextFlags_CallbackResize)
    .value("CALLBACK_EDIT", ImGuiInputTextFlags_CallbackEdit)
    .value("ESCAPE_CLEARS_ALL", ImGuiInputTextFlags_EscapeClearsAll);

In addition, I have a function binding declare like this:

    m.def("input_text", [](const char* label, std::string text, ImGuiInputTextFlags_ flags_) { 
        int flags = (int)flags_;
        IM_ASSERT((flags & ImGuiInputTextFlags_CallbackResize) == 0);
        flags |= ImGuiInputTextFlags_CallbackResize;

        ImGuiInputTextCallback callback = nullptr;
        void* user_data = nullptr;

        InputTextCallback_UserData cb_user_data;
        cb_user_data.Str = &text;
        cb_user_data.ChainCallback = callback;

        cb_user_data.ChainCallbackUserData = user_data;
        bool changed = ImGui::InputText(label, (char*)text.c_str(), text.capacity() + 1, flags, InputTextCallback, &cb_user_data);
        return std::pair(changed, text);
    }, "label"_a, "text"_a, "flags"_a = ImGuiInputTextFlags_None);

The type stub for the input_text function becomes:

def input_text(label: str, text: str, flags: InputTextFlags = <InputTextFlags.NONE: 0>) -> tuple[bool, str]: ...

I was expecting the above to be

def input_text(label: str, text: str, flags: InputTextFlags = InputTextFlags.NONE -> tuple[bool, str]: ...

Fortunately, I can fix this by declaring the flags argument like this: "flags"_a.sig("InputTextFlags.NONE") = ImGuiInputTextFlags_None.

But is this actually a bug in how the stubs get rendered? According to the Nanobind docs on arg &sig(const char *sig), the signature would be rendered with str(value): "Override the signature of the default argument value. This is useful when the argument value is unusually complex so that the default method to explain it in docstrings and stubs (str(value)) does not produce acceptable output."

And actually if I use str() to render the NONE field, I get the expected output:

>>> import imgui
>>> imgui.InputTextFlags
<enum 'InputTextFlags'>
>>> imgui.InputTextFlags.NONE
<InputTextFlags.NONE: 0>
>>> str(imgui.InputTextFlags.NONE)
'InputTextFlags.NONE'

[wjakob]

It's annoying how enum.* render by default. I ended up changing the behavior for compatibility with nanobind 1.x. See 36eebac