perf: avoid duplicate provider metadata fetch on stop

The previous implementation fetched the provider binary path and
metadata twice per service during `compose stop`: once in stop.go
to gate on the `stop` capability, and again inside runPlugin via
setupPluginCommand.

setupPluginCommand now signals "skip" by returning (nil, nil) when
the requested command is absent from the provider's metadata.
stop.go calls runPlugin directly; the skip-when-unadvertised check
moves into runPlugin.

Addresses PR #13779 review feedback.

Signed-off-by: Guillaume Lours <[email protected]>

docs/extension.md

@@ -111,8 +111,8 @@ The provider is responsible for releasing all resources associated with the serv
 
 When the user runs `docker compose stop`, Compose invokes `<provider> compose --project-name <NAME> stop <SERVICE>` for each
 provider-backed service in reverse dependency order. The provider should pause the resource without releasing it, so a later
-`docker compose start` or `docker compose up` can resume it. Any `setenv` JSON message returned during `stop` is ignored,
-since dependent services are also stopping.
+`docker compose up` can resume it (note that `docker compose start` only restarts existing containers and does not invoke
+provider hooks). Any `setenv` JSON message returned during `stop` is ignored, since dependent services are also stopping.
 
 The `stop` hook is opt-in: Compose invokes it only when the provider declares a `stop` block in its `metadata` subcommand
 output. Providers that do not advertise `stop` in metadata (or do not implement the `metadata` subcommand at all) are

pkg/compose/plugins.go

@@ -66,6 +66,9 @@ func (s *composeService) runPlugin(ctx context.Context, project *types.Project,
 	if err != nil {
 		return err
 	}
+	if cmd == nil {
+		return nil
+	}
 
 	variables, err := s.executePlugin(cmd, command, service)
 	if err != nil {
@@ -188,9 +191,10 @@ func (s *composeService) setupPluginCommand(ctx context.Context, project *types.
 	case "down":
 		currentCommandMetadata = cmdOptionsMetadata.Down
 	case "stop":
-		if cmdOptionsMetadata.Stop != nil {
-			currentCommandMetadata = *cmdOptionsMetadata.Stop
+		if cmdOptionsMetadata.Stop == nil {
+			return nil, nil
 		}
+		currentCommandMetadata = *cmdOptionsMetadata.Stop
 	}
 
 	provider := *service.Provider

pkg/compose/stop.go

@@ -54,14 +54,6 @@ func (s *composeService) stop(ctx context.Context, projectName string, options a
 		}
 		serv := project.Services[service]
 		if serv.Provider != nil {
-			path, err := s.getPluginBinaryPath(serv.Provider.Type)
-			if err != nil {
-				return err
-			}
-			metadata := s.getPluginMetadata(path, serv.Provider.Type, project)
-			if metadata.Stop == nil {
-				return nil
-			}
 			return s.runPlugin(ctx, project, serv, "stop")
 		}
 		return s.stopContainers(ctx, &serv, containers.filter(isService(service)).filter(isNotOneOff), options.Timeout, event)