add Lifecycle.RequireUnique methods for load-once deps

lifecycle.go

@@ -123,6 +123,12 @@ func (app *Lifecycle) Require(modules ...*Module) error {
 	return app.RequireL(app.logger, modules...)
 }
 
+// RequireUnique is the same as Require, but it returns an error if any requested
+// module is already set up--rather than ignoring it.
+func (app *Lifecycle) RequireUnique(modules ...*Module) error {
+	return app.RequireUniqueL(app.logger, modules...)
+}
+
 // RequireL adds module(s) to the lifecycle with a specific logger and
 // immediately runs any setup functions. See Require for more details.
 // This variation is useful when you need to set up modules with a non-
@@ -163,6 +169,23 @@ func (app *Lifecycle) RequireL(logger *slog.Logger, modules ...*Module) error {
 	return nil
 }
 
+// RequireUniqueL is the same as RequireL, but it returns an error if any requested
+// module is already set up--rather than ignoring it.
+func (app *Lifecycle) RequireUniqueL(logger *slog.Logger, modules ...*Module) error {
+	// Check if any module is already set up
+	for _, mod := range modules {
+		if mod == nil {
+			return fmt.Errorf("module is nil")
+		}
+
+		if _, ok := app.setupTracker[mod.name]; ok {
+			return fmt.Errorf("module '%s' is already set up, cannot require it again", mod.name)
+		}
+	}
+
+	return app.RequireL(logger, modules...)
+}
+
 // setupSingle is a helper function to set up a single module. Returns an error
 // if the module cannot be set up or if dependencies are not satisfied.
 func (app *Lifecycle) setupSingle(mod *Module, logger *slog.Logger) error {