Is it possible to provide an WrapProcess API in v9?

[win5do]

Problem

I want to achieve two functionalities, but I found that I can't do it using go-redis/v9.

1. If ctx has a stress test flag, change the key to a shadow key

I want replace client's Process to hook all Command.

type clientWrap struct {
	redis.UniversalClient
}

func (s *clientWrap) Process(ctx context.Context, cmd redis.Cmder) error {
	return s.UniversalClient.Process(ctx, rewriteCmder(ctx, cmd))
}

go-redis/v9 Hook API can't change origin redis.Cmder, can only create a new redis.Cmder, which may affect the value obtained by the outermost API.

func (redisHook) ProcessHook(hook redis.ProcessHook) redis.ProcessHook {
	return func(ctx context.Context, cmd redis.Cmder) error {
		fmt.Printf("starting processing: <%s>\n", cmd)
		err := hook(ctx, cmd)
		fmt.Printf("finished processing: <%s>\n", cmd)
		return err
	}
}

func (c *Client) Process(ctx context.Context, cmd Cmder) error {
	err := c.processHook(ctx, cmd)
	cmd.SetErr(err)
	return err
}

If you can overwrite Process, you can do this easily and safely. In v6 version WrapProcess API is available.

// go-redis/v6
// WrapProcess wraps function that processes Redis commands.
func (c *baseClient) WrapProcess(
	fn func(oldProcess func(cmd Cmder) error) func(cmd Cmder) error,
) {
	c.process = fn(c.process)
}

2. Implement interface like Pipeliner

I am working on migrating some old projects and hope to provide a v9 to v6 API bridge layer to reduce the modification of old code.

Pipeliner need to implement all method in Cmdable, it would be much easier if cmdable could be overwrite like in v9 code.

func (c *Pipeline) init() {
	c.cmdable = c.Process
	c.statefulCmdable = c.Process
}

// go-redis/v6
type Cmdable interface {
	Pipeline() Pipeliner
	Pipelined(fn func(Pipeliner) error) ([]Cmder, error)

	TxPipelined(fn func(Pipeliner) error) ([]Cmder, error)
	TxPipeline() Pipeliner
        
        // ...
}

type Pipeliner interface {
	StatefulCmdable
	Do(args ...interface{}) *Cmd
	Process(cmd Cmder) error
	Close() error
	Discard() error
	Exec() ([]Cmder, error)
}

Request

Provide an API to modify Process similar to WrapProcess in go-reids/v6.

Or do any of you have alternative solutions?

[ndyakov]

Hello @win5do, I will review why this functionality was dropped and get back to you. In the meantime, can you provide me an example of the usecase you are describing.

[win5do]

WrapProcess API is used as a hook in v6 version and was removed probably because of the new Hook API.

What kind of usecase is needed? I described two usecases above.