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

pkg/gotenberg/pdfengine.go

@@ -3,6 +3,7 @@ package gotenberg
 import (
 	"context"
 	"errors"
+	"fmt"
 
 	"go.uber.org/zap"
 )
@@ -27,12 +28,27 @@ var (
 	// ErrPdfEncryptionNotSupported is returned when encryption
 	// is not supported by the PDF engine.
 	ErrPdfEncryptionNotSupported = errors.New("encryption not supported")
-
-	// ErrPdfEngineEncryptionPasswordsNotSupported is returned when provided
-	// passwords are not supported by the PDF engine.
-	ErrPdfEngineEncryptionPasswordsNotSupported = errors.New("passwords not supported")
 )
 
+// PdfEngineInvalidArgsError represents an error returned by a PDF engine when
+// invalid arguments are provided. It includes the name of the engine and a
+// detailed message describing the issue.
+type PdfEngineInvalidArgsError struct {
+	engine string
+	msg    string
+}
+
+// Error implements the error interface.
+func (e *PdfEngineInvalidArgsError) Error() string {
+	return fmt.Sprintf("%s: %s", e.engine, e.msg)
+}
+
+// NewPdfEngineInvalidArgs creates a new PdfEngineInvalidArgsError with the
+// given engine name and message.
+func NewPdfEngineInvalidArgs(engine, msg string) error {
+	return &PdfEngineInvalidArgsError{engine, msg}
+}
+
 const (
 	// SplitModeIntervals represents a mode where a PDF is split at specific
 	// intervals.

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.