Ugly patched version of Blenders unregister tool function that I can't get to work

unregister_tool.py

class ToolNotRegisteredError(Exception):
    """Adding special exception to be able to only catch this special exception"""
    pass
  
def unregister_tool(tool_cls):
    space_type = tool_cls.bl_space_type
    context_mode = tool_cls.bl_context_mode

    from bl_ui.space_toolsystem_common import (
        ToolSelectPanelHelper,
        ToolDef,
    )
    cls = ToolSelectPanelHelper._tool_class_from_space_type(space_type)
    if cls is None:
        raise Exception("Space type %r has no toolbar" % space_type)
    tools = cls._tools[context_mode]
    
    def get_tool_def(tool_list, bl_idname):
        for definition in tool_list:
            if definition is None:
                continue
            if isinstance(definition, ToolDef):
                if definition.idname == bl_idname:
                    return definition, definition
            else:
                for child_definition in definition:
                    if child_definition.idname == bl_idname:
                        return definition, child_definition
        return None, None
    if hasattr(tool_cls, "_bl_tool"):
         _tool_def = tool_def = tool_cls._bl_tool
    else:
        _tool_def, tool_def = get_tool_def(tools, tool_cls.bl_idname)
    if not tool_def:
        raise ToolNotRegisteredError("bpy.utils.unregister_tool: could not find %r (may not be registered)" % tool_cls.bl_idname)

    try:
        i = tools.index(_tool_def)
    except ValueError:
        i = -1

    def tool_list_clean(tool_list):
        # Trim separators.
        while tool_list and tool_list[-1] is None:
            del tool_list[-1]
        while tool_list and tool_list[0] is None:
            del tool_list[0]
        # Remove duplicate separators.
        for i in range(len(tool_list) - 1, -1, -1):
            is_none = tool_list[i] is None
            if is_none and prev_is_none:
                del tool_list[i]
            prev_is_none = is_none

    changed = False
    if i != -1:
        del tools[i]
        tool_list_clean(tools)
        changed = True

    if not changed:
        for i, item in enumerate(tools):
            if isinstance(item, tuple):
                try:
                    j = item.index(tool_def)
                except ValueError:
                    j = -1

                if j != -1:
                    item_clean = list(item)
                    del item_clean[j]
                    tool_list_clean(item_clean)
                    if item_clean:
                        tools[i] = tuple(item_clean)
                    else:
                        del tools[i]
                        tool_list_clean(tools)
                    del item_clean

                    # tuple(sub_item for sub_item in items if sub_item is not tool_def)
                    changed = True
                    break

    if not changed:
        raise Exception("Unable to remove %r" % tool_cls)
        
    if hasattr(tool_cls, "_bl_tool"):
        del tool_cls._bl_tool 

    keymap_data = tool_def.keymap
    if keymap_data is not None:
        from bpy import context
        wm = context.window_manager
        keyconfigs = wm.keyconfigs
        for kc in (keyconfigs.default, keyconfigs.addon):
            km = kc.keymaps.get(keymap_data[0])
            if km is None:
                print("Warning keymap %r not found in %r!" % (keymap_data[0], kc.name))
            else:
                kc.keymaps.remove(km)
    

unregister_tool_bug.md

The template Ui Tools Simple, throws an exception if ran multiple times in a row.
Exception: Tool 'my_template.my_circle_select' already exists!

And if you try to unregister it before registering it throws a different error. AttributeError: type object 'MyTool' has no attribute '_bl_tool'

This "patch" fixes this error but you will have to unregistering before registering your tool first.

This does seem to be a bug in blender. This is the line it crashes on https://github.com/blender/blender/blob/aec56e562a2799ea764671206f7b3b889b69829d/release/scripts/modules/bpy/utils/__init__.py#L954 The register_tool function is adding that to the class instance at https://github.com/blender/blender/blob/aec56e562a2799ea764671206f7b3b889b69829d/release/scripts/modules/bpy/utils/__init__.py#L872 If it is added to the class instance it makes sense that it isn't there on the uninstantiated class.
I wonder if the bpy.utils.register_class (so for a class and not tool) is calling the corresponding unregister function within it self not to get a "Already registed error" when running from the text editor.

usage.py

import bpy
from bpy.types import WorkSpaceTool

class MyTool(WorkSpaceTool):
    pass

if __name__ == "__main__":
    try:
        unregister_tool(MyTool)
    except ToolNotRegisteredError:
        pass
    bpy.utils.register_tool(MyTool)