How to use protoc-gen-validate (PGV) with connect-go ?

[s-takehana]

How to use protoc-gen-validate (PGV) with connect-go ?

I want to call Validate / ValidateAll in interceptor func.

[s-takehana]

type validator interface {
	ValidateAll() error
}

func NewValidationInterceptor() connect.UnaryInterceptorFunc {
	interceptor := func(next connect.UnaryFunc) connect.UnaryFunc {
		return connect.UnaryFunc(func(ctx context.Context, req connect.AnyRequest) (connect.AnyResponse, error) {
			if v, ok := req.Any().(validator); ok {
				if err := v.ValidateAll(); err != nil {
					return nil, connect.NewError(connect.CodeInvalidArgument, err)
				}
			}
			return next(ctx, req)
		})
	}
	return connect.UnaryInterceptorFunc(interceptor)
}

[akshayjshah]

Nope, you definitely can validate messages - the interceptor would wrap StreamingHandlerConn or StreamingClientConn, and validate each time a message is sent or received.

[ymmt2005]

Understood. Thank you!

[ymmt2005]

I ended up with something like

type interceptor struct{}

func (i *interceptor) WrapStreamingHandler(next connect.StreamingHandlerFunc) connect.StreamingHandlerFunc {
	return func(ctx context.Context, conn connect.StreamingHandlerConn) error {
		return next(ctx, validatingHandlerConn{conn})
	}
}

type validatingHandlerConn struct {
	connect.StreamingHandlerConn
}

func (conn validatingHandlerConn) Receive(a any) error {
	if err := conn.StreamingHandlerConn.Receive(a); err != nil {
		return err
	}
	// call Validate or ValidateAll ...
	return nil
}

[akshayjshah]

That looks about right!

[s-takehana]

validate-go is useful for protovalidate users.