fix(qpdf): allow warnings (#1135)

* Optionally allow warnings in QPDF operations

* warnings are not errors by default

* Apply suggestions from code review

Co-authored-by: Julien Neuhart <neuhart.julien@gmail.com>

* fix some merge artifacts

* follow the args convention

---------

Co-authored-by: Julien Neuhart <neuhart.julien@gmail.com>

pkg/modules/qpdf/qpdf.go

@@ -23,6 +23,7 @@ func init() {
 // interface.
 type QPdf struct {
 	binPath    string
+	globalArgs []string
 }
 
 // Descriptor returns a [QPdf]'s module descriptor.
@@ -41,6 +42,8 @@ func (engine *QPdf) Provision(ctx *gotenberg.Context) error {
 	}
 
 	engine.binPath = binPath
+	// Warnings should not cause errors.
+	engine.globalArgs = []string{"--warning-exit-0"}
 
 	return nil
 }
@@ -88,7 +91,10 @@ func (engine *QPdf) Split(ctx context.Context, logger *zap.Logger, mode gotenber
 		if !mode.Unify {
 			return nil, fmt.Errorf("split PDFs using mode '%s' without unify with QPDF: %w", mode.Mode, gotenberg.ErrPdfSplitModeNotSupported)
 		}
-		args = append(args, inputPath, "--pages", ".", mode.Span, "--", outputPath)
+		args = append(args, inputPath)
+		args = append(args, engine.globalArgs...)
+		args = append(args, "--pages", ".", mode.Span)
+		args = append(args, "--", outputPath)
 	default:
 		return nil, fmt.Errorf("split PDFs using mode '%s' with QPDF: %w", mode.Mode, gotenberg.ErrPdfSplitModeNotSupported)
 	}
@@ -110,6 +116,7 @@ func (engine *QPdf) Split(ctx context.Context, logger *zap.Logger, mode gotenber
 func (engine *QPdf) Merge(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
 	var args []string
 	args = append(args, "--empty")
+	args = append(args, engine.globalArgs...)
 	args = append(args, "--pages")
 	args = append(args, inputPaths...)
 	args = append(args, "--", outputPath)
@@ -131,10 +138,11 @@ func (engine *QPdf) Merge(ctx context.Context, logger *zap.Logger, inputPaths []
 // original annotations.
 func (engine *QPdf) Flatten(ctx context.Context, logger *zap.Logger, inputPath string) error {
 	var args []string
+	args = append(args, inputPath)
 	args = append(args, "--generate-appearances")
 	args = append(args, "--flatten-annotations=all")
 	args = append(args, "--replace-input")
-	args = append(args, inputPath)
+	args = append(args, engine.globalArgs...)
 
 	cmd, err := gotenberg.CommandContext(ctx, logger, engine.binPath, args...)
 	if err != nil {

pkg/modules/qpdf/qpdf_test.go

@@ -154,6 +154,15 @@ func TestQPdf_Merge(t *testing.T) {
 			},
 			expectError: false,
 		},
+		{
+			scenario: "success even with warnings",
+			ctx:      context.TODO(),
+			inputPaths: []string{
+				"/tests/test/testdata/pdfengines/sample1.pdf",
+				"/tests/test/testdata/pdfengines/sample5.pdf",
+			},
+			expectError: false,
+		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
 			engine := new(QPdf)
@@ -236,6 +245,14 @@ func TestQPdf_Split(t *testing.T) {
 			expectError:            false,
 			expectOutputPathsCount: 1,
 		},
+		{
+			scenario:               "success even with warnings",
+			ctx:                    context.TODO(),
+			mode:                   gotenberg.SplitMode{Mode: gotenberg.SplitModePages, Span: "1-2", Unify: true},
+			inputPath:              "/tests/test/testdata/pdfengines/sample5.pdf",
+			expectError:            false,
+			expectOutputPathsCount: 1,
+		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
 			engine := new(QPdf)
@@ -304,6 +321,13 @@ func TestQPdf_Flatten(t *testing.T) {
 			createCopy:  true,
 			expectError: false,
 		},
+		{
+			scenario:    "success even with warnings",
+			ctx:         context.TODO(),
+			inputPath:   "/tests/test/testdata/pdfengines/sample5.pdf",
+			createCopy:  true,
+			expectError: false,
+		},
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
 			engine := new(QPdf)