event backend none: return an error when reading events

podman --events-backend none events should return with an error since it
will never be able to actually list events.

Fixes part three of #15688

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

2 files changed, 8 insertions, 7 deletions

diff --git a/libpod/events/events_linux.go b/libpod/events/events_linux.go
index b11467aca..66b125dd5 100644
--- a/libpod/events/events_linux.go
+++ b/libpod/events/events_linux.go
@@ -20,7 +20,7 @@ func NewEventer(options EventerOptions) (Eventer, error) {
 	case strings.ToUpper(LogFile.String()):
 		return newLogFileEventer(options)
 	case strings.ToUpper(Null.String()):
-		return NewNullEventer(), nil
+		return newNullEventer(), nil
 	case strings.ToUpper(Memory.String()):
 		return NewMemoryEventer(), nil
 	default:
diff --git a/libpod/events/nullout.go b/libpod/events/nullout.go
index 587a1b98b..da3820c23 100644
--- a/libpod/events/nullout.go
+++ b/libpod/events/nullout.go
@@ -2,10 +2,11 @@ package events
 
 import (
 	"context"
+	"errors"
 )
 
-// EventToNull is an eventer type that only performs write operations
-// and only writes to /dev/null. It is meant for unittests only
+// EventToNull is an eventer type that does nothing.
+// It is meant for unittests only
 type EventToNull struct{}
 
 // Write eats the event and always returns nil
@@ -13,14 +14,14 @@ func (e EventToNull) Write(ee Event) error {
 	return nil
 }
 
-// Read does nothing. Do not use it.
+// Read does nothing and returns an error.
 func (e EventToNull) Read(ctx context.Context, options ReadOptions) error {
-	return nil
+	return errors.New("cannot read events with the \"none\" backend")
 }
 
-// NewNullEventer returns a new null eventer.  You should only do this for
+// newNullEventer returns a new null eventer.  You should only do this for
 // the purposes of internal libpod testing.
-func NewNullEventer() Eventer {
+func newNullEventer() Eventer {
 	return EventToNull{}
 }