gofr-dev/gofr · error

validate func is empty

Error message

validate func is empty

What it means

errValidateFuncEmpty is returned by NewAPIKeyAuthProviderWithValidateFunc and NewBasicAuthProviderWithValidateFunc when the provided validate callback is nil. Without a validation function the provider has no way to decide whether credentials are valid, so construction fails immediately. It is a programming/config error at setup time.

Source

Thrown at pkg/gofr/http/middleware/auth.go:30

// AuthMethod represents a custom type to define the different authentication methods supported.
type AuthMethod int

const (
	JWTClaim AuthMethod = iota // JWTClaim represents the key used to store JWT claims within the request context.
	Username
	APIKey

	// #nosec G101
	headerXAPIKey       = "X-Api-Key"
	headerAuthorization = "Authorization"

	dummyValue = "dummy"
)

var (
	errContainerNil      = errors.New("container is nil")
	errValidateFuncEmpty = errors.New("validate func is empty")
)

// AuthHeaders returns the request header names GoFr's authentication middleware reads. It is the
// single source of truth for callers that must forward a request's identity — e.g. the MCP server
// re-dispatching a tool call through the router.
func AuthHeaders() []string {
	return []string{headerAuthorization, headerXAPIKey}
}

type AuthProvider interface {
	GetAuthMethod() AuthMethod
	ExtractAuthHeader(r *http.Request) (any, ErrorHTTP)
}

// AuthMiddleware creates a middleware function that enforces authentication based on the method provided.
func AuthMiddleware(a AuthProvider) func(handler http.Handler) http.Handler {
	return func(handler http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {

View on GitHub (pinned to 187eb24962)

Solutions

1. Pass a non-nil validation function to the constructor
2. If the validator is dynamic, initialize a default implementation before wiring middleware
3. Assert the function is non-nil at startup; fail fast with a clear log message
4. Add a test covering the constructor with your real validator wiring

Example fix

// before
var validate func(c *container.Container, user, pass string) bool
provider, _ := middleware.NewBasicAuthProviderWithValidateFunc(c, validate) // errValidateFuncEmpty
// after
validate := func(c *container.Container, user, pass string) bool {
    return c != nil && checkCredentials(user, pass)
}
provider, err := middleware.NewBasicAuthProviderWithValidateFunc(c, validate)

if validateFunc == nil {
    return errors.New("validate func must be provided to auth provider constructor")
}

func hasValidator(fn func(*container.Container, string, string) bool) bool { return fn != nil }

provider, err := middleware.NewAPIKeyAuthProviderWithValidateFunc(c, fn)
if err != nil {
    if errors.Is(err, middleware.ErrValidateFuncEmpty) {
        log.Fatal("no validate function wired for auth provider")
    }
    return err
}

When it happens

Trigger: Calling NewAPIKeyAuthProviderWithValidateFunc(c, nil) or NewBasicAuthProviderWithValidateFunc(c, nil), e.g. when the callback is conditionally assigned and ends up nil.

Common situations: Function variables resolved from config/flags that were never set, refactors that removed the assignment, or test scaffolding that forgot to inject a stub validator.

Related errors

• api keys list is empty
• user list is empty
• unsupported config file format
• %w: negative offset %d
• out of range

AI-assisted analysis of gofr-dev/gofr@187eb24962 (2026-09-01). Data as JSON: /api/errors/a1c9c73fc07b5050. Report an issue: GitHub.