fix: fail global deployment if no matchine machines found, improve caddy deploy output in particular

internal/cli/client/deploy.go

@@ -30,6 +30,8 @@ type Plan struct {
 // machines that should be included.
 type MachineFilter func(m *pb.MachineInfo) bool
 
+var ErrNoMatchingMachines = errors.New("no machines match the filter")
+
 // NewDeployment creates a new deployment for the given service specification.
 // If strategy is nil, a default RollingStrategy will be used.
 func (cli *Client) NewDeployment(spec api.ServiceSpec, strategy Strategy) (*Deployment, error) {
@@ -81,7 +83,7 @@ func (d *Deployment) Plan(ctx context.Context) (Plan, error) {
 
 	plan, err := d.Strategy.Plan(ctx, d.cli, d.Service, d.Spec)
 	if err != nil {
-		return Plan{}, fmt.Errorf("create plan using %T: %w", d.Strategy, err)
+		return Plan{}, fmt.Errorf("create plan using %s strategy: %w", d.Strategy.Type(), err)
 	}
 	d.plan = &plan
 

internal/cli/client/strategy.go

@@ -13,6 +13,8 @@ import (
 // Strategy defines how a service should be deployed or updated. Different implementations can provide various
 // deployment patterns such as rolling updates, blue/green deployments, etc.
 type Strategy interface {
+	// Type returns the type of the deployment strategy, e.g. "rolling", "blue-green".
+	Type() string
 	// Plan returns the operation to reconcile the service to the desired state.
 	// If the service does not exist (new deployment), svc will be nil.
 	Plan(ctx context.Context, cli *Client, svc *api.Service, spec api.ServiceSpec) (Plan, error)
@@ -25,6 +27,10 @@ type RollingStrategy struct {
 	MachineFilter MachineFilter
 }
 
+func (s *RollingStrategy) Type() string {
+	return "rolling"
+}
+
 func (s *RollingStrategy) Plan(
 	ctx context.Context, cli *Client, svc *api.Service, spec api.ServiceSpec,
 ) (Plan, error) {
@@ -81,6 +87,9 @@ func (s *RollingStrategy) planGlobal(
 		machines = slices.DeleteFunc(machines, func(m *pb.MachineMember) bool {
 			return !s.MachineFilter(m.Machine)
 		})
+		if len(machines) == 0 {
+			return plan, ErrNoMatchingMachines
+		}
 	}
 
 	// TODO: figure out how to return a warning if there are machines down. Embed the machinesDown in the plan?