django2.X 路由兼容 include模块书写规范

使用以往框架的项目路由urls文件

    urlpatterns = [
    url(r'^user/',include('user.urls', namespace='user')),
    url(r'^',include('goods.urls',namespace='goods')),
]

报错, 错误信息:

    Specifying a namespace in include() without providing an app_name is not supported. Set the app_name attribute in the included module, or pass a 2-tuple containing the list of patterns and app_name instead.

解决方法:
    分别单独设置url路由文件路径, app_name应用名称 以及 namespace名称空间.
    格式如下:

    urlpatterns = [
    url(r'^user/',include(('user.urls', 'user'), namespace='user')),
    url(r'^',include(('goods.urls', 'goods'), namespace='goods')),
]

    或者

    设置应用url路由文件路径和 app_name. 没有设置的namespace与app_name属性同名.
    格式一如下:(需要在应用url路由文件中添加变量 app_name=['应用名'] )

    urlpatterns = [
    url(r'^user/',include('user.urls')),
    url(r'^',include('goods.urls')),
]

　
    格式二如下:

    urlpatterns = [
    url(r'^user/',include(('user.urls', 'user'), )),
    url(r'^',include(('goods.urls', 'goods'), )),
]

其中app_name属性可以通过include传入, 也可以单独设置在每个应用url路由文件中. 请根据解耦需要自行选择.

----------------------------------------

原因分析
   
查看源代码

可得知:
    django2.X中, 在include模块里, 重新规定了输入规范,app_name应用名称必须填写.
    
    include要求的三个参数:

    urlconf_module,url文件路径
    app_name,包名
    namespace,命名空间

　书写格式为:

include((urlconf_module,app_name),namespace)
urlconf_module,app_name包含在第一个参数的元组中, 第二参数namespace则应是字符串

    三个属性中:
    urlconf_module和app_name必须传入,app_name可以在父url文件传入也可在子url文件单独定义.
   namespace, 可传可不传.

    不可以只传入namespace!
　

源码片段:

def include(arg, namespace=None, app_name=None):
    if app_name and not namespace:
        raise ValueError('Must specify a namespace if specifying app_name.')

    if isinstance(arg, tuple):
        # callable returning a namespace hint
        if namespace:
            raise ImproperlyConfigured('Cannot override the namespace for a dynamic module that provides a namespace')
        urlconf_module, app_name, namespace = arg
    else:
        # No namespace hint - use manually provided namespace
        urlconf_module = arg

    if isinstance(urlconf_module, six.string_types):
        urlconf_module = import_module(urlconf_module)
    patterns = getattr(urlconf_module, 'urlpatterns', urlconf_module)

    # Make sure we can iterate through the patterns (without this, some
    # testcases will break).
    if isinstance(patterns, (list, tuple)):
        for url_pattern in patterns:
            # Test if the LocaleRegexURLResolver is used within the include;
            # this should throw an error since this is not allowed!
            if isinstance(url_pattern, LocaleRegexURLResolver):
                raise ImproperlyConfigured(
                    'Using i18n_patterns in an included URLconf is not allowed.')

    return (urlconf_module, app_name, namespace)

def include(arg, namespace=None):
    app_name = None
    if isinstance(arg, tuple):
        # Callable returning a namespace hint.
        try:
            urlconf_module, app_name = arg
        except ValueError:
            if namespace:
                raise ImproperlyConfigured(
                    'Cannot override the namespace for a dynamic module that '
                    'provides a namespace.'
                )
            raise ImproperlyConfigured(
                'Passing a %d-tuple to include() is not supported. Pass a '
                '2-tuple containing the list of patterns and app_name, and '
                'provide the namespace argument to include() instead.' % len(arg)
            )
    else:
        # No namespace hint - use manually provided namespace.
        urlconf_module = arg

    if isinstance(urlconf_module, str):
        urlconf_module = import_module(urlconf_module)
    patterns = getattr(urlconf_module, 'urlpatterns', urlconf_module)
    app_name = getattr(urlconf_module, 'app_name', app_name)
    if namespace and not app_name:
        raise ImproperlyConfigured(
            'Specifying a namespace in include() without providing an app_name '
            'is not supported. Set the app_name attribute in the included '
            'module, or pass a 2-tuple containing the list of patterns and '
            'app_name instead.',
        )
    namespace = namespace or app_name
    # Make sure the patterns can be iterated through (without this, some
    # testcases will break).
    if isinstance(patterns, (list, tuple)):
        for url_pattern in patterns:
            pattern = getattr(url_pattern, 'pattern', None)
            if isinstance(pattern, LocalePrefixPattern):
                raise ImproperlyConfigured(
                    'Using i18n_patterns in an included URLconf is not allowed.'
                )
    return (urlconf_module, app_name, namespace)