Require configuration selectors only for applicable scopes

selectors.go

@@ -27,10 +27,15 @@ func configInputFlags[C any](suite ConfigSuite[C], formatDefault string) []Flag[
 }
 
 func adaptSelector[C any](selector Selector[C]) Flag[configInput[C]] {
-	return adaptContextSelector(selector,
+	flag := adaptContextSelector(selector,
 		func(input *configInput[C]) *C { return &input.SelectorContext },
 		func(input *configInput[C], state selectorState[C]) { input.selectors = append(input.selectors, state) },
 	)
+	if flag.binding.meta.Required {
+		flag.binding.meta.Required = false // Scope-aware preflight enforces this requirement.
+		flag.binding.meta.Usage += " (required where applicable)"
+	}
+	return flag
 }
 
 func adaptContextSelector[C any, I any](selector Selector[C], selectContext func(*I) *C, record func(*I, selectorState[C])) Flag[I] {
@@ -53,6 +58,8 @@ func adaptContextSelector[C any, I any](selector Selector[C], selectContext func
 				return nil, err
 			}
 			state := selectorState[C]{
+				name:     binding.meta.Name,
+				required: binding.meta.Required,
 				scopes:   append([]string(nil), selector.Scopes...),
 				supplied: len(values) > 0,
 				apply:    apply,
@@ -128,9 +135,6 @@ func selectConfigScopes[C any](suite ConfigSuite[C], input configInput[C], opera
 		}
 	}
 	for _, selector := range input.selectors {
-		if !selector.supplied {
-			continue
-		}
 		applies := false
 		for _, scopeName := range scopes {
 			if selectorApplies(selector.scopes, scopeName) {
@@ -138,7 +142,10 @@ func selectConfigScopes[C any](suite ConfigSuite[C], input configInput[C], opera
 				break
 			}
 		}
-		if !applies {
+		if applies && selector.required && !selector.supplied {
+			return nil, fmt.Errorf("required flag --%s was not supplied", selector.name)
+		}
+		if selector.supplied && !applies {
 			return nil, fmt.Errorf("selector is not applicable to configuration scope %q", input.Scope)
 		}
 	}