Compile effective flag aliases during installation

registry.go

@@ -18,10 +18,12 @@ func (a *App) Register(declarations ...Declaration) error {
 }
 
 type installationCandidate struct {
-	commands     map[string]*commandNode
-	routingRules []RoutingRule
-	aliases      *internalalias.Resolver
-	changed      bool
+	commands       map[string]*commandNode
+	routingRules   []RoutingRule
+	aliases        *internalalias.Resolver
+	flagAliases    map[string]resolvedFlagAliases
+	discoveryFlags map[string]resolvedFlagAliases
+	changed        bool
 }
 
 type canonicalNode struct {
@@ -81,6 +83,8 @@ func (a *App) installBatch(declarations ...Declaration) error {
 	a.commands = candidate.commands
 	a.routingRules = candidate.routingRules
 	a.aliases = candidate.aliases
+	a.flagAliases = candidate.flagAliases
+	a.discoveryFlags = candidate.discoveryFlags
 	a.snapshot = nil
 	return nil
 }
@@ -138,12 +142,24 @@ func (a *App) buildInstallationCandidate(commands []Command, addedRules []Routin
 	if err := validateCommandAliases(rules, resolver, tree); err != nil {
 		return nil, err
 	}
+	flagAliases, discoveryFlags, err := compileFlagAliases(rules, tree, resolver)
+	if err != nil {
+		return nil, err
+	}
+	candidate.flagAliases = flagAliases
+	candidate.discoveryFlags = discoveryFlags
 	return candidate, nil
 }
 
 func normalizeRoutingRules(rules []RoutingRule) ([]RoutingRule, error) {
 	unique := make(map[routingRuleKey]RoutingRule, len(rules))
 	commandTargets := make(map[string]string)
+	type scopedFlagKey struct {
+		kind   routingRuleKind
+		scope  string
+		source string
+	}
+	flagTargets := make(map[scopedFlagKey]string)
 	for _, rule := range rules {
 		if rule.record == nil {
 			return nil, fmt.Errorf("invalid zero routing rule declaration")
@@ -160,6 +176,12 @@ func normalizeRoutingRules(rules []RoutingRule) ([]RoutingRule, error) {
 				return nil, fmt.Errorf("conflicting command aliases for %q", rule.record.sourcePath.String())
 			}
 			commandTargets[key.source] = key.target
+		} else {
+			scopeKey := scopedFlagKey{kind: key.kind, scope: key.scope, source: key.source}
+			if previous, exists := flagTargets[scopeKey]; exists && previous != key.target {
+				return nil, fmt.Errorf("conflicting flag aliases for %q", rule.record.sourceFlag.token())
+			}
+			flagTargets[scopeKey] = key.target
 		}
 		unique[key] = rule
 	}