better message formatting

api/pkg/merrors/errors.go

@@ -3,6 +3,7 @@ package merrors
 import (
 	"errors"
 	"fmt"
+	"strings"
 
 	"go.mongodb.org/mongo-driver/bson/primitive"
 )
@@ -27,8 +28,8 @@ func Internal(msg string) error {
 
 var ErrInvalidArg = errors.New("invalidArgError")
 
-func InvalidArgument(msg string) error {
-	return fmt.Errorf("%w: %s", ErrInvalidArg, msg)
+func InvalidArgument(msg string, argumentNames ...string) error {
+	return fmt.Errorf("%w: %s", ErrInvalidArg, invalidArgumentMessage(msg, argumentNames...))
 }
 
 var ErrDataConflict = errors.New("DataConflict")
@@ -64,8 +65,8 @@ func NoMessagingTopic(topic string) error {
 	return fmt.Errorf("%w: messaging topic '%s' not found", ErrNoMessagingTopic, topic)
 }
 
-func InvalidArgumentWrap(err error, msg string) error {
-	return wrapError(ErrInvalidArg, msg, err)
+func InvalidArgumentWrap(err error, msg string, argumentNames ...string) error {
+	return wrapError(ErrInvalidArg, invalidArgumentMessage(msg, argumentNames...), err)
 }
 
 func InternalWrap(err error, msg string) error {
@@ -79,3 +80,23 @@ func wrapError(base error, msg string, err error) error {
 	}
 	return errors.Join(baseErr, err)
 }
+
+func invalidArgumentMessage(msg string, argumentNames ...string) string {
+	names := make([]string, 0, len(argumentNames))
+	for _, name := range argumentNames {
+		name = strings.TrimSpace(name)
+		if name == "" {
+			continue
+		}
+		names = append(names, fmt.Sprintf("%q", name))
+	}
+	if len(names) == 0 {
+		return msg
+	}
+
+	prefix := "broken argument"
+	if len(names) > 1 {
+		prefix = "broken arguments"
+	}
+	return fmt.Sprintf("%s %s: %s", prefix, strings.Join(names, ", "), msg)
+}

api/pkg/merrors/errors_test.go

@@ -0,0 +1,47 @@
+package merrors
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+func TestInvalidArgumentSupportsBrokenArgumentName(t *testing.T) {
+	t.Run("without argument name keeps old behavior", func(t *testing.T) {
+		err := InvalidArgument("value is missing")
+		expected := "invalidArgError: value is missing"
+		if err.Error() != expected {
+			t.Fatalf("unexpected error message: %s", err)
+		}
+		if !errors.Is(err, ErrInvalidArg) {
+			t.Fatalf("error should wrap ErrInvalidArg")
+		}
+	})
+
+	t.Run("single argument name", func(t *testing.T) {
+		err := InvalidArgument("value is missing", "bot_token_env")
+		expected := `invalidArgError: broken argument "bot_token_env": value is missing`
+		if err.Error() != expected {
+			t.Fatalf("unexpected error message: %s", err)
+		}
+	})
+
+	t.Run("multiple argument names", func(t *testing.T) {
+		err := InvalidArgument("value mismatch", "bot_token_env", "chat_id_env", " ")
+		expected := `invalidArgError: broken arguments "bot_token_env", "chat_id_env": value mismatch`
+		if err.Error() != expected {
+			t.Fatalf("unexpected error message: %s", err)
+		}
+	})
+}
+
+func TestInvalidArgumentWrapSupportsBrokenArgumentName(t *testing.T) {
+	base := errors.New("root cause")
+	err := InvalidArgumentWrap(base, "value is missing", "bot_token_env")
+	if !strings.Contains(err.Error(), `invalidArgError: broken argument "bot_token_env": value is missing`) {
+		t.Fatalf("wrapped error should include broken argument name: %s", err)
+	}
+	if !errors.Is(err, ErrInvalidArg) || !errors.Is(err, base) {
+		t.Fatalf("wrapped error should preserve all error layers")
+	}
+}