chore(pdfengines): better custom error message if invalid args

pkg/modules/api/middlewares.go

@@ -61,6 +61,11 @@ func ParseError(err error) (int, string) {
 		return http.StatusBadRequest, "At least one PDF engine cannot process the requested metadata, while others may have failed to convert due to different issues"
 	}
 
+	var invalidArgsError *gotenberg.PdfEngineInvalidArgsError
+	if errors.As(err, &invalidArgsError) {
+		return http.StatusBadRequest, invalidArgsError.Error()
+	}
+
 	var httpErr HttpError
 	if errors.As(err, &httpErr) {
 		return httpErr.HttpError()

pkg/modules/pdfengines/routes.go

@@ -270,16 +270,6 @@ func EncryptPdfStub(ctx *api.Context, engine gotenberg.PdfEngine, userPassword,
 	for _, inputPath := range inputPaths {
 		err := engine.Encrypt(ctx, ctx.Log(), inputPath, userPassword, ownerPassword)
 		if err != nil {
-			if errors.Is(err, gotenberg.ErrPdfEngineEncryptionPasswordsNotSupported) {
-				return api.WrapError(
-					err,
-					api.NewSentinelHttpError(
-						http.StatusBadRequest,
-						"Invalid form data: both 'userPassword' and 'ownerPassword' form fields must be provided and different",
-					),
-				)
-			}
-
 			return fmt.Errorf("encrypt PDF '%s': %w", inputPath, err)
 		}
 	}

pkg/modules/pdftk/pdftk.go

@@ -152,7 +152,7 @@ func (engine *PdfTk) Encrypt(ctx context.Context, logger *zap.Logger, inputPath,
 	}
 
 	if ownerPassword == userPassword || ownerPassword == "" {
-		return gotenberg.ErrPdfEngineEncryptionPasswordsNotSupported
+		return gotenberg.NewPdfEngineInvalidArgs("pdftk", "both 'userPassword' and 'ownerPassword' must be provided and different. Consider switching to another PDF engine if this behavior does not work with your workflow")
 	}
 
 	// Create a temp output file in the same directory.