Make a seat pass no repair, read every machine before passing, keep the gate's pass in memory (issue 1317, review round 1)

cmd/mesh-controller/seat_pass.go

@@ -73,23 +73,31 @@ func seatPassHandAct(p catalogue.SeatPass) link.HandAct {
 	}
 }
 
-// theMeshPassesSeatsOn is passSeatsOn as the composition runs it: against the store's record, with the hand act
-// on the bus. Said to where the composition says its other lines (sayLeftOut).
-func theMeshPassesSeatsOn(ctx context.Context, inv *inventory.Inventory, shelf map[string]catalogue.Manifest,
-	assigned map[string][]string, holdings []catalogue.Held) []catalogue.Held {
-	var assignments []catalogue.Assignment
+// assignmentsOf are the assignments of every machine, as the passing of a seat reads them. **A module assigned and
+// missing from the shelf is still assigned**: it is an assignment with no claims, so its holder is not taken for gone.
+func assignmentsOf(shelf map[string]catalogue.Manifest, assigned map[string][]string) []catalogue.Assignment {
+	var out []catalogue.Assignment
 	for node, modules := range assigned {
 		for _, module := range modules {
-			if m, ok := shelf[module]; ok {
-				assignments = append(assignments, catalogue.Assignment{Node: node, Manifest: m})
+			m, ok := shelf[module]
+			if !ok {
+				m = catalogue.Manifest{Module: module}
 			}
+			out = append(out, catalogue.Assignment{Node: node, Manifest: m})
 		}
 	}
-	var w io.Writer = os.Stderr
-	if lw, ok := ctx.Value(leftOutKey{}).(io.Writer); ok {
-		w = lw
+	return out
+}
+
+// seatPassingOn is how a composition on this inventory passes a seat: against the store's record with the hand act
+// on the bus, or, on a throwaway mesh (the merge gate's), in memory only, writing nothing anywhere.
+func seatPassingOn(inv *inventory.Inventory, w io.Writer) seatPassing {
+	if inv.Throwaway() {
+		return seatPassing{say: w,
+			pass: func(context.Context, catalogue.SeatPass) (bool, error) { return true, nil },
+			act:  func(context.Context, catalogue.SeatPass) error { return nil }}
 	}
-	return passSeatsOn(ctx, seatPassing{
+	return seatPassing{
 		say: w,
 		pass: func(ctx context.Context, p catalogue.SeatPass) (bool, error) {
 			return inv.PassSeat(ctx, p.Seat.Name, p.Seat.Scope, p.From, p.To)
@@ -100,5 +108,22 @@ func theMeshPassesSeatsOn(ctx context.Context, inv *inventory.Inventory, shelf m
 				return err
 			})
 		},
-	}, holdings, assignments)
+	}
+}
+
+// theMeshPassesSeatsOn is passSeatsOn as the composition runs it. **Only when every machine's assignments were
+// read** (assignedErr nil): a machine whose read failed would look as if its modules were assigned nowhere, and
+// its holder would lose the seat. Said to where the composition says its other lines (sayLeftOut).
+func theMeshPassesSeatsOn(ctx context.Context, inv *inventory.Inventory, shelf map[string]catalogue.Manifest,
+	assigned map[string][]string, assignedErr error, holdings []catalogue.Held) []catalogue.Held {
+	var w io.Writer = os.Stderr
+	if lw, ok := ctx.Value(leftOutKey{}).(io.Writer); ok {
+		w = lw
+	}
+	if assignedErr != nil {
+		fmt.Fprintf(w, "no seat is passed on in this composition: a machine's assignments could not be read, so a "+
+			"holder on record might look assigned nowhere: %v\n", assignedErr)
+		return holdings
+	}
+	return passSeatsOn(ctx, seatPassingOn(inv, w), holdings, assignmentsOf(shelf, assigned))
 }