return ErrProcessorNotFound error if procesor not found

backends/gateway.go

@@ -12,6 +12,8 @@ import (
 	"strings"
 )
 
+var ErrProcessorNotFound error
+
 // A backend gateway is a proxy that implements the Backend interface.
 // It is used to start multiple goroutine workers for saving mail, and then distribute email saving to the workers
 // via a channel. Shutting down via Shutdown() will stop all workers.
@@ -142,7 +144,7 @@ func (gw *BackendGateway) Reinitialize() error {
 // Decorators are functions of Decorator type, source files prefixed with p_*
 // Each decorator does a specific task during the processing stage.
 // This function uses the config value process_stack to figure out which Decorator to use
-func (gw *BackendGateway) newProcessorLine() Processor {
+func (gw *BackendGateway) newProcessorLine() (Processor, error) {
 	var decorators []Decorator
 	cfg := strings.ToLower(strings.TrimSpace(gw.gwConfig.ProcessorStack))
 	if len(cfg) == 0 {
@@ -153,11 +155,14 @@ func (gw *BackendGateway) newProcessorLine() Processor {
 		name := line[len(line)-1-i] // reverse order, since decorators are stacked
 		if makeFunc, ok := processors[name]; ok {
 			decorators = append(decorators, makeFunc())
+		} else {
+			ErrProcessorNotFound = errors.New(fmt.Sprintf("processor [%s] not found", name))
+			return nil, ErrProcessorNotFound
 		}
 	}
 	// build the call-stack of decorators
 	p := Decorate(DefaultProcessor{}, decorators...)
-	return p
+	return p, nil
 }
 
 // loadConfig loads the config for the GatewayConfig
@@ -187,7 +192,11 @@ func (gw *BackendGateway) Initialize(cfg BackendConfig) error {
 		}
 		var lines []Processor
 		for i := 0; i < workersSize; i++ {
-			lines = append(lines, gw.newProcessorLine())
+			p, err := gw.newProcessorLine()
+			if err != nil {
+				return err
+			}
+			lines = append(lines, p)
 		}
 		// initialize processors
 		if err := Svc.initialize(cfg); err != nil {