          ]
  
  
  class OrderingFilter(BaseFilterBackend):
      # The URL query parameter used for the ordering.
      ordering_param = api_settings.ORDERING_PARAM
      ordering_fields = None
 
</s> remove         for path, method, view in view_endpoints:
            if not self.has_view_permissions(path, method, view):
                continue
            link = view.schema.get_link(path, method, base_url=self.url)
            subpath = path[len(prefix):]
            keys = self.get_keys(subpath, method, view)
            insert_into(links, keys, link)
 </s> add     def create_view(self, callback, method, request=None):
        """
        Given a callback, return an actual view instance.
        """
        view = callback.cls(**getattr(callback, 'initkwargs', {}))
        view.args = ()
        view.kwargs = {}
        view.format_kwarg = None
        view.request = None
        view.action_map = getattr(callback, 'actions', None) </s> remove     def get_count(self, queryset):
        """
        Determine an object count, supporting either querysets or regular lists.
        """
        try:
            return queryset.count()
        except (AttributeError, TypeError):
            return len(queryset)
 </s> add     def get_schema_operation_parameters(self, view):
        parameters = [
            {
                'name': self.limit_query_param,
                'required': False,
                'in': 'query',
                'description': force_text(self.limit_query_description),
                'schema': {
                    'type': 'integer',
                },
            },
            {
                'name': self.offset_query_param,
                'required': False,
                'in': 'query',
                'description': force_text(self.offset_query_description),
                'schema': {
                    'type': 'integer',
                },
            },
        ]
        return parameters </s> remove     def get_link(self, path, method, base_url):
        """
        Generate `coreapi.Link` for self.view, path and method.

        This is the main _public_ access point.

        Parameters:

        * path: Route path for view from URLConf.
        * method: The HTTP request method.
        * base_url: The project "mount point" as given to SchemaGenerator
        """
        raise NotImplementedError(".get_link() must be overridden.")


class AutoSchema(ViewInspector):
    """
    Default inspector for APIView

    Responsible for per-view introspection and schema generation.
    """
    def __init__(self, manual_fields=None):
        """
        Parameters:

        * `manual_fields`: list of `coreapi.Field` instances that
            will be added to auto-generated fields, overwriting on `Field.name`
        """
        super().__init__()
        if manual_fields is None:
            manual_fields = []
        self._manual_fields = manual_fields

    def get_link(self, path, method, base_url):
        fields = self.get_path_fields(path, method)
        fields += self.get_serializer_fields(path, method)
        fields += self.get_pagination_fields(path, method)
        fields += self.get_filter_fields(path, method)

        manual_fields = self.get_manual_fields(path, method)
        fields = self.update_fields(fields, manual_fields)

        if fields and any([field.location in ('form', 'body') for field in fields]):
            encoding = self.get_encoding(path, method)
        else:
            encoding = None

        description = self.get_description(path, method)

        if base_url and path.startswith('/'):
            path = path[1:]

        return coreapi.Link(
            url=parse.urljoin(base_url, path),
            action=method.lower(),
            encoding=encoding,
            fields=fields,
            description=description
        )

    def get_description(self, path, method):
        """
        Determine a link description.

        This will be based on the method docstring if one exists,
        or else the class docstring.
        """
        view = self.view

        method_name = getattr(view, 'action', method.lower())
        method_docstring = getattr(view, method_name, None).__doc__
        if method_docstring:
            # An explicit docstring on the method or action.
            return self._get_description_section(view, method.lower(), formatting.dedent(smart_text(method_docstring)))
        else:
            return self._get_description_section(view, getattr(view, 'action', method.lower()), view.get_view_description())

    def _get_description_section(self, view, header, description):
        lines = [line for line in description.splitlines()]
        current_section = ''
        sections = {'': ''}

        for line in lines:
            if header_regex.match(line):
                current_section, seperator, lead = line.partition(':')
                sections[current_section] = lead.strip()
            else:
                sections[current_section] += '\n' + line

        # TODO: SCHEMA_COERCE_METHOD_NAMES appears here and in `SchemaGenerator.get_keys`
        coerce_method_names = api_settings.SCHEMA_COERCE_METHOD_NAMES
        if header in sections:
            return sections[header].strip()
        if header in coerce_method_names:
            if coerce_method_names[header] in sections:
                return sections[coerce_method_names[header]].strip()
        return sections[''].strip()

    def get_path_fields(self, path, method):
        """
        Return a list of `coreapi.Field` instances corresponding to any
        templated path variables.
        """
        view = self.view
        model = getattr(getattr(view, 'queryset', None), 'model', None)
        fields = []

        for variable in uritemplate.variables(path):
            title = ''
            description = ''
            schema_cls = coreschema.String
            kwargs = {}
            if model is not None:
                # Attempt to infer a field description if possible.
                try:
                    model_field = model._meta.get_field(variable)
                except Exception:
                    model_field = None

                if model_field is not None and model_field.verbose_name:
                    title = force_text(model_field.verbose_name)

                if model_field is not None and model_field.help_text:
                    description = force_text(model_field.help_text)
                elif model_field is not None and model_field.primary_key:
                    description = get_pk_description(model, model_field)

                if hasattr(view, 'lookup_value_regex') and view.lookup_field == variable:
                    kwargs['pattern'] = view.lookup_value_regex
                elif isinstance(model_field, models.AutoField):
                    schema_cls = coreschema.Integer

            field = coreapi.Field(
                name=variable,
                location='path',
                required=True,
                schema=schema_cls(title=title, description=description, **kwargs)
            )
            fields.append(field)

        return fields

    def get_serializer_fields(self, path, method):
        """
        Return a list of `coreapi.Field` instances corresponding to any
        request body input, as determined by the serializer class.
        """
        view = self.view

        if method not in ('PUT', 'PATCH', 'POST'):
            return []

        if not hasattr(view, 'get_serializer'):
            return []

        try:
            serializer = view.get_serializer()
        except exceptions.APIException:
            serializer = None
            warnings.warn('{}.get_serializer() raised an exception during '
                          'schema generation. Serializer fields will not be '
                          'generated for {} {}.'
                          .format(view.__class__.__name__, method, path))

        if isinstance(serializer, serializers.ListSerializer):
            return [
                coreapi.Field(
                    name='data',
                    location='body',
                    required=True,
                    schema=coreschema.Array()
                )
            ]

        if not isinstance(serializer, serializers.Serializer):
            return []

        fields = []
        for field in serializer.fields.values():
            if field.read_only or isinstance(field, serializers.HiddenField):
                continue

            required = field.required and method != 'PATCH'
            field = coreapi.Field(
                name=field.field_name,
                location='form',
                required=required,
                schema=field_to_schema(field)
            )
            fields.append(field)

        return fields

    def get_pagination_fields(self, path, method):
        view = self.view

        if not is_list_view(path, method, view):
            return []

        pagination = getattr(view, 'pagination_class', None)
        if not pagination:
            return []

        paginator = view.pagination_class()
        return paginator.get_schema_fields(view)

    def _allows_filters(self, path, method):
        """
        Determine whether to include filter Fields in schema.

        Default implementation looks for ModelViewSet or GenericAPIView
        actions/methods that cause filtering on the default implementation.

        Override to adjust behaviour for your view.

        Note: Introduced in v3.7: Initially "private" (i.e. with leading underscore)
            to allow changes based on user experience.
        """
        if getattr(self.view, 'filter_backends', None) is None:
            return False

        if hasattr(self.view, 'action'):
            return self.view.action in ["list", "retrieve", "update", "partial_update", "destroy"]

        return method.lower() in ["get", "put", "patch", "delete"]

    def get_filter_fields(self, path, method):
        if not self._allows_filters(path, method):
            return []

        fields = []
        for filter_backend in self.view.filter_backends:
            fields += filter_backend().get_schema_fields(self.view)
        return fields

    def get_manual_fields(self, path, method):
        return self._manual_fields

    @staticmethod
    def update_fields(fields, update_with):
        """
        Update list of coreapi.Field instances, overwriting on `Field.name`.

        Utility function to handle replacing coreapi.Field fields
        from a list by name. Used to handle `manual_fields`.

        Parameters:

        * `fields`: list of `coreapi.Field` instances to update
        * `update_with: list of `coreapi.Field` instances to add or replace.
        """
        if not update_with:
            return fields

        by_name = OrderedDict((f.name, f) for f in fields)
        for f in update_with:
            by_name[f.name] = f
        return list(by_name.values())

    def get_encoding(self, path, method):
        """
        Return the 'encoding' parameter to use for a given endpoint.
        """
        view = self.view

        # Core API supports the following request encodings over HTTP...
        supported_media_types = {
            'application/json',
            'application/x-www-form-urlencoded',
            'multipart/form-data',
        }
        parser_classes = getattr(view, 'parser_classes', [])
        for parser_class in parser_classes:
            media_type = getattr(parser_class, 'media_type', None)
            if media_type in supported_media_types:
                return media_type
            # Raw binary uploads are supported with "application/octet-stream"
            if media_type == '*/*':
                return 'application/octet-stream'

        return None


class ManualSchema(ViewInspector):
    """
    Allows providing a list of coreapi.Fields,
    plus an optional description.
    """
    def __init__(self, fields, description='', encoding=None):
        """
        Parameters:

        * `fields`: list of `coreapi.Field` instances.
        * `description`: String description for view. Optional.
        """
        super().__init__()
        assert all(isinstance(f, coreapi.Field) for f in fields), "`fields` must be a list of coreapi.Field instances"
        self._fields = fields
        self._description = description
        self._encoding = encoding

    def get_link(self, path, method, base_url):

        if base_url and path.startswith('/'):
            path = path[1:]

        return coreapi.Link(
            url=parse.urljoin(base_url, path),
            action=method.lower(),
            encoding=self._encoding,
            fields=self._fields,
            description=self._description
        )

 </s> add 
    def get_schema_operation_parameters(self, view):
        return [
            {
                'name': self.search_param,
                'required': False,
                'in': 'query',
                'description': force_text(self.search_description),
                'schema': {
                    'type': 'string',
                },
            },
        ]

          ]
  
    def get_schema_operation_parameters(self, view):
        return [
            {
                'name': self.search_param,
                'required': False,
                'in': 'query',
                'description': force_text(self.search_description),
                'schema': {
                    'type': 'string',
                },
            },
        ]

  
  class OrderingFilter(BaseFilterBackend):
      # The URL query parameter used for the ordering.
      ordering_param = api_settings.ORDERING_PARAM
      ordering_fields = None
keep add keep keep keep keep keep
 Added OpenAPI Schema Generation. (#6532)

Co-authored-by: Lucidiot <lucidiot@protonmail.com>
Co-authored-by: dongfangtianyu <dongfangtianyu@qq.com> 
rest_framework/filters.py