ingress: fix crash when parsing from stdin

When injecting a single email or an mbox from stdin, ParseMail is
invoked with the wrong context object which does not have a reference to
the event bus.

This results in a NULL pointer dereference on Queries.Commit():

	for _, e := range q.pendingEvents {
		q.Events.Enqueue(&e) // q.Events is nil
	}

Use the correct context object to fix the issue.

Add a panic() to ensure that transactions can never be started with
a nil event bus anymore.

Fixes: 82a9d25 ("ingress: pass context with event bus to SMTP mail parser")
Reported-by: Thomas Bracht Laumann Jespersen <t@laumann.xyz>
Signed-off-by: Robin Jarry <robin@jarry.cc>

Author: rjarry

cmd/pw/ingress/main.go

@@ -63,15 +63,15 @@ func (c *CLI) Run(ctx *pw.Context) error {
 				if err != nil {
 					break
 				}
-				err = mail.ParseMail(ctx, ctx.DB, msg, c.ListID)
+				err = mail.ParseMail(ctx.Context, ctx.DB, msg, c.ListID)
 				if errors.As(err, &dupErr) {
 					log.Debugf("ignoring %s", err)
 				} else if err != nil {
 					break
 				}
 			}
 		} else {
-			err = mail.ParseMail(ctx, ctx.DB, os.Stdin, c.ListID)
+			err = mail.ParseMail(ctx.Context, ctx.DB, os.Stdin, c.ListID)
 		}
 		if errors.As(err, &dupErr) {
 			log.Debugf("ignoring %s", err)

pkg/db/db.go

@@ -124,10 +124,11 @@ func WithBus(ctx context.Context, bus EventBus) context.Context {
 }
 
 func GetBus(ctx context.Context) EventBus {
-	if bus, ok := ctx.Value(busCtxKey{}).(EventBus); ok {
-		return bus
+	bus := ctx.Value(busCtxKey{}).(EventBus)
+	if bus == nil {
+		panic("Queries.Begin() context has no event bus value")
 	}
-	return nil
+	return bus
 }
 
 // Queries provides typed database access methods. It wraps a bun.IDB