import bpy


class TestImport(bpy.types.Operator):
    bl_idname = "import.test"
    bl_label = "Test Import"
    
    filepath: bpy.props.StringProperty(subtype='FILE_PATH', options={'SKIP_SAVE', 'HIDDEN'})
    directory: bpy.props.StringProperty(subtype='FILE_PATH', options={'SKIP_SAVE', 'HIDDEN'})
    files: bpy.props.CollectionProperty(type=bpy.types.OperatorFileListElement, options={'SKIP_SAVE', 'HIDDEN'})

    test_prop: bpy.props.BoolProperty(name="Test Prop", default=False)

    @classmethod
    def poll(cls, context):
        return (context.region and context.region.type == 'WINDOW')

    def execute(self, context):
        return {'FINISHED'}

    def invoke(self, context, event):
        if self.properties.is_property_set("filepath") or self.properties.is_property_set("directory"):
            return context.window_manager.invoke_props_dialog(self)
        context.window_manager.fileselect_add(self)
        return {'RUNNING_MODAL'}



class TEST_FH_import(bpy.types.FileHandler):
    bl_idname = "TEST_FH_import"
    bl_label = "File handler test"
    bl_import_operator = "import.test"
    bl_file_extensions = ".txt"

    @classmethod
    def poll_drop(cls, context):
        return (context.region and context.region.type == 'WINDOW')


bpy.utils.register_class(TestImport)
bpy.utils.register_class(TEST_FH_import)