🤗 [Question]: How to skip a handler function if the auth middleware fails and directly skip to response handler?

[balanikaran]

Question Description

I'm having the code structure like this below:

someRouter.Use(auth.SomeAuthMiddleware)

someRouter.Post(
	"/someEndpoint",
	controller.SomeEndpointHandler,
	genericResponseHandler.GenericJSONResponseHandler,
)

What I want is, if my Auth Middleware fails for some reason, my SomeEndpointHandler should not run, and it should directly skip to the GenericJSONResponseHandler with the set status code.

Is that even possible? Or is my approach of code design is correct or not?

Code Snippet (optional)

No response

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[ReneWerner87]

fail with "panic" or error?

if you want your handlers to continue, you would have to catch these errors, react to them and ignore them in the flow and put some information in the locals(https://docs.gofiber.io/api/ctx#locals) that you can use later for skipping

[balanikaran]

Yeah, I'm just setting the relevant status_code in the locals and then skipping the handlers by checking in the very beginning of the following handlers. I just wanted to know if there is any short-circuiting kind of pattern available.

[ReneWerner87]

I just wanted to know if there is any short-circuiting kind of pattern available. no i think not @efectn @Trim21 any other ideas ?

[trim21]

So if I understand correctly, you want GenericJSONResponseHandler to be executed but not SomeEndpointHandler when SomeAuthMiddleware failed to authorized current request.

Common case for this is to just response (or return a error) in the SomeAuthMiddleware and don't' call c.Next(), so the middleware and handler after this middleware won't be executed by nature.

Guessing from your handler name, the GenericJSONResponseHandler is used to create final response,

You can use a middleware GenericJSONResponseMiddleware and add it before auth middleware, use a customized error, return it in your auth middleware and use errors.As to check if the error is expected error type.

would look like this:

type myError struct {
	Code     int
	Message  string
	Response any
}

func (e myError) Error() string {
	return e.Message
}

func GenericJSONResponseHandler(c *fiber.Ctx) error {
	err := c.Next()

	var ef myError
	if errors.As(err, &ef) {
		return c.Status(ef.Code).JSON(ef.Response)
	}

	return err
}

var logined bool

func SomeAuthMiddleware(c *fiber.Ctx) error {
	if !logined {
		return myError{
			Code:     http.StatusUnauthorized,
			Message:  "",
			Response: fiber.Map{"err": "not login"},
		}
	}

	return c.Next()
}

[balanikaran]

Hey, thanks for the solution here, let me evaluate if we can use it in our code.

This was really helpful. :)

[efectn]

If you have some questions more, feel free to reopen the issue.