Harden action handler registration for nk0

2 files changed, 34 insertions, 1 deletions

diff --git a/internal/hexaiaction/action_handler.go b/internal/hexaiaction/action_handler.go
index 8da90ea..c01edbd 100644
--- a/internal/hexaiaction/action_handler.go
+++ b/internal/hexaiaction/action_handler.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"reflect"
 	"sync"
 
 	"codeberg.org/snonux/hexai/internal/appconfig"
@@ -28,6 +29,9 @@ type CodeActionHandler = ActionHandler
 type actionHandlerFunc func(context.Context, actionRequest) (string, error)
 
 func (f actionHandlerFunc) Execute(ctx context.Context, req actionRequest) (string, error) {
+	if f == nil {
+		return "", fmt.Errorf("hexaiaction: nil action handler")
+	}
 	return f(ctx, req)
 }
 
@@ -44,7 +48,7 @@ func (r *actionHandlerRegistry) register(kind ActionKind, handler ActionHandler)
 	if kind == "" {
 		panic("hexaiaction: cannot register empty action kind")
 	}
-	if handler == nil {
+	if isNilActionHandler(handler) {
 		panic(fmt.Sprintf("hexaiaction: cannot register nil handler for %q", kind))
 	}
 
@@ -56,6 +60,20 @@ func (r *actionHandlerRegistry) register(kind ActionKind, handler ActionHandler)
 	r.handlers[kind] = handler
 }
 
+func isNilActionHandler(handler ActionHandler) bool {
+	if handler == nil {
+		return true
+	}
+
+	value := reflect.ValueOf(handler)
+	switch value.Kind() {
+	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Pointer, reflect.Slice:
+		return value.IsNil()
+	default:
+		return false
+	}
+}
+
 func (r *actionHandlerRegistry) lookup(kind ActionKind) (ActionHandler, bool) {
 	r.mu.RLock()
 	defer r.mu.RUnlock()
diff --git a/internal/hexaiaction/action_handler_test.go b/internal/hexaiaction/action_handler_test.go
index 1d811fe..92df3b1 100644
--- a/internal/hexaiaction/action_handler_test.go
+++ b/internal/hexaiaction/action_handler_test.go
@@ -55,6 +55,10 @@ func TestActionHandlerRegistryRejectsInvalidRegistrations(t *testing.T) {
 		"nil handler": func(registry *actionHandlerRegistry) {
 			registry.register(ActionKind("nil"), nil)
 		},
+		"typed nil handler": func(registry *actionHandlerRegistry) {
+			var handler actionHandlerFunc
+			registry.register(ActionKind("typed-nil"), handler)
+		},
 		"duplicate kind": func(registry *actionHandlerRegistry) {
 			registry.register(ActionKind("dup"), actionHandlerFunc(handleSkipAction))
 			registry.register(ActionKind("dup"), actionHandlerFunc(handleSkipAction))
@@ -85,3 +89,14 @@ func TestActionHandlerRegistryNilPanicNamesKind(t *testing.T) {
 	}()
 	newActionHandlerRegistry().register(ActionCustom, nil)
 }
+
+func TestActionHandlerFuncNilExecuteReturnsError(t *testing.T) {
+	var handler actionHandlerFunc
+	_, err := handler.Execute(context.Background(), actionRequest{})
+	if err == nil {
+		t.Fatal("expected error")
+	}
+	if !strings.Contains(err.Error(), "nil action handler") {
+		t.Fatalf("expected nil handler error, got %v", err)
+	}
+}