What causes "no field %s found" in grpc-ecosystem/grpc-gateway?

Use the fully-qualified field name: pkg.Message.field

no field %s found

Error message

no field %s found

What it means

Field-level options are validated against a map of fully-qualified field names (FQFN) built from all registered messages. If opts.Field names a field whose qualified name is not present, this error is returned and option registration aborts.

Source

Thrown at internal/descriptor/registry.go:812

	for _, opt := range opts.Service {
		qualifiedService := "." + opt.Service
		if _, ok := services[qualifiedService]; !ok {
			return fmt.Errorf("no service %s found", opt.Service)
		}
		r.serviceOptions[qualifiedService] = opt.Option
	}

	// build map of all registered fields
	fields := make(map[string]struct{})
	for _, m := range r.msgs {
		for _, f := range m.Fields {
			fields[f.FQFN()] = struct{}{}
		}
	}
	for _, opt := range opts.Field {
		qualifiedField := "." + opt.Field
		if _, ok := fields[qualifiedField]; !ok {
			return fmt.Errorf("no field %s found", opt.Field)
		}
		r.fieldOptions[qualifiedField] = opt.Option
	}
	return nil
}

// GetOpenAPIFileOption returns a registered OpenAPI option for a file
func (r *Registry) GetOpenAPIFileOption(file string) (*options.Swagger, bool) {
	opt, ok := r.fileOptions[file]
	return opt, ok
}

// GetOpenAPIMethodOption returns a registered OpenAPI option for a method
func (r *Registry) GetOpenAPIMethodOption(qualifiedMethod string) (*options.Operation, bool) {
	opt, ok := r.methodOptions[qualifiedMethod]
	return opt, ok
}

View on GitHub (pinned to a58a4436a3)

Solutions

Use the fully-qualified field name: pkg.Message.field
Verify the field still exists on the message in the loaded protos
Update the options entry after schema refactors
Compare your field list against the registry's collected FQFNs

Example fix

// before
Field: "Book.title"
// after
Field: "examples.library.v1.Book.title"

Defensive patterns

Strategy: validation

Validate before calling

want := "." + opt.Field
if !knownFields[want] {
    return fmt.Errorf("field %q not found; use pkg.Message.field", opt.Field)
}
err = reg.RegisterOptions(opts)

Prevention

Use fully-qualified field names (pkg.Message.field) in options entries
Update options entries in the same change that renames or removes fields
Generate the field list from descriptors instead of hand-writing it

When it happens

Trigger: Registering options with opts.Field referencing a field that does not exist, is misspelled, is missing package/message qualification, or whose message lives in an unloaded file.

Common situations: Field renamed or removed from a message; qualifying only by message name without package; targeting a field inside a oneof/nested message with an incorrect path; options shared across repos with diverging schemas.

Related errors

AI-assisted analysis of grpc-ecosystem/grpc-gateway@a58a4436a3 (2026-09-02). Data as JSON: /api/errors/93f0d0a87bd9c3f3. Report an issue: GitHub.