fix(cli): make command registration snapshot-safe

Co-Authored-By: Virgil <virgil@lethean.io>

pkg/cli/commands.go

@@ -105,15 +105,23 @@ func loadLocaleSources(sources ...LocaleSource) {
 func RegisteredLocales() []fs.FS {
 	registeredCommandsMu.Lock()
 	defer registeredCommandsMu.Unlock()
-	return registeredLocales
+	if len(registeredLocales) == 0 {
+		return nil
+	}
+	out := make([]fs.FS, len(registeredLocales))
+	copy(out, registeredLocales)
+	return out
 }
 
 // RegisteredCommands returns an iterator over the registered command functions.
 func RegisteredCommands() iter.Seq[CommandRegistration] {
 	return func(yield func(CommandRegistration) bool) {
 		registeredCommandsMu.Lock()
-		defer registeredCommandsMu.Unlock()
-		for _, fn := range registeredCommands {
+		snapshot := make([]CommandRegistration, len(registeredCommands))
+		copy(snapshot, registeredCommands)
+		registeredCommandsMu.Unlock()
+
+		for _, fn := range snapshot {
 			if !yield(fn) {
 				return
 			}
@@ -125,10 +133,12 @@ func RegisteredCommands() iter.Seq[CommandRegistration] {
 // Called by Init() after creating the root command.
 func attachRegisteredCommands(root *cobra.Command) {
 	registeredCommandsMu.Lock()
-	defer registeredCommandsMu.Unlock()
+	snapshot := make([]CommandRegistration, len(registeredCommands))
+	copy(snapshot, registeredCommands)
+	commandsAttached = true
+	registeredCommandsMu.Unlock()
 
-	for _, fn := range registeredCommands {
+	for _, fn := range snapshot {
 		fn(root)
 	}
-	commandsAttached = true
 }

pkg/cli/commands_test.go

@@ -148,6 +148,26 @@ func TestRegisterCommands_Bad(t *testing.T) {
 		require.NoError(t, err)
 		assert.Equal(t, "late", cmd.Use)
 	})
+
+	t.Run("nested registration during startup does not deadlock", func(t *testing.T) {
+		resetGlobals(t)
+
+		RegisterCommands(func(root *cobra.Command) {
+			root.AddCommand(&cobra.Command{Use: "outer", Short: "Outer"})
+			RegisterCommands(func(root *cobra.Command) {
+				root.AddCommand(&cobra.Command{Use: "inner", Short: "Inner"})
+			})
+		})
+
+		err := Init(Options{AppName: "test"})
+		require.NoError(t, err)
+
+		for _, name := range []string{"outer", "inner"} {
+			cmd, _, err := RootCmd().Find([]string{name})
+			require.NoError(t, err)
+			assert.Equal(t, name, cmd.Use)
+		}
+	})
 }
 
 // TestLocaleLoading_Good verifies locale files become available to the active i18n service.