webhook: resulting file was deleted because of defer outside of goroutine

internal/app/api/api.go

@@ -87,11 +87,12 @@ func newContext(r *resource) (context.Context, context.CancelFunc) {
 func print(c echo.Context, p printer.Printer, r *resource) error {
 	baseFilename, err := rand.Get()
 	if err != nil {
-		return fmt.Errorf("getting result file name: %v", err)
+		return hijackErr(fmt.Errorf("getting result file name: %v", err), r)
 	}
 	filename := fmt.Sprintf("%s.pdf", baseFilename)
 	fpath := fmt.Sprintf("%s/%s", r.dirPath, filename)
 	if r.webhookURL() == "" {
+		defer r.removeAll()
 		// if no webhook URL given, run conversion
 		// and directly return the resulting PDF file
 		// or an error.
@@ -104,6 +105,7 @@ func print(c echo.Context, p printer.Printer, r *resource) error {
 	// run the following lines in a goroutine so that
 	// it doesn't block.
 	go func() {
+		defer r.removeAll()
 		if err := p.Print(fpath); err != nil {
 			c.Logger().Errorf("%v", err)
 			return
@@ -123,3 +125,10 @@ func print(c echo.Context, p printer.Printer, r *resource) error {
 	}()
 	return nil
 }
+
+func hijackErr(err error, r *resource) error {
+	if r != nil {
+		defer r.removeAll()
+	}
+	return err
+}

internal/app/api/html.go

@@ -8,9 +8,8 @@ import (
 func convertHTML(c echo.Context) error {
 	r, err := newResource(c)
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
-	defer r.removeAll()
 	ctx, cancel := newContext(r)
 	if cancel != nil {
 		defer cancel()
@@ -18,26 +17,26 @@ func convertHTML(c echo.Context) error {
 	p := &printer.HTML{Context: ctx}
 	indexPath, err := r.filePath("index.html")
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	p.WithLocalURL(indexPath)
 	headerPath, _ := r.filePath("header.html")
 	if err := p.WithHeaderFile(headerPath); err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	footerPath, _ := r.filePath("footer.html")
 	if err := p.WithFooterFile(footerPath); err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	paperSize, err := r.paperSize()
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	p.PaperWidth = paperSize[0]
 	p.PaperHeight = paperSize[1]
 	paperMargins, err := r.paperMargins()
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	p.MarginTop = paperMargins[0]
 	p.MarginBottom = paperMargins[1]
@@ -45,7 +44,7 @@ func convertHTML(c echo.Context) error {
 	p.MarginRight = paperMargins[3]
 	landscape, err := r.landscape()
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	p.Landscape = landscape
 	return print(c, p, r)

internal/app/api/markdown.go

@@ -8,35 +8,34 @@ import (
 func convertMarkdown(c echo.Context) error {
 	r, err := newResource(c)
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
-	defer r.removeAll()
 	ctx, cancel := newContext(r)
 	if cancel != nil {
 		defer cancel()
 	}
 	indexPath, err := r.filePath("index.html")
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	p := &printer.Markdown{Context: ctx, TemplatePath: indexPath}
 	headerPath, _ := r.filePath("header.html")
 	if err := p.WithHeaderFile(headerPath); err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	footerPath, _ := r.filePath("footer.html")
 	if err := p.WithFooterFile(footerPath); err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	paperSize, err := r.paperSize()
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	p.PaperWidth = paperSize[0]
 	p.PaperHeight = paperSize[1]
 	paperMargins, err := r.paperMargins()
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	p.MarginTop = paperMargins[0]
 	p.MarginBottom = paperMargins[1]
@@ -44,7 +43,7 @@ func convertMarkdown(c echo.Context) error {
 	p.MarginRight = paperMargins[3]
 	landscape, err := r.landscape()
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	p.Landscape = landscape
 	return print(c, p, r)

internal/app/api/merge.go

@@ -1,6 +1,7 @@
 package api
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 	"os"
@@ -13,20 +14,23 @@ import (
 func merge(c echo.Context) error {
 	r, err := newResource(c)
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
-	defer r.removeAll()
 	fpaths, err := r.filePaths([]string{".pdf"})
 	if err != nil {
-		return err
+		return hijackErr(err, r)
+	}
+	if len(fpaths) == 0 {
+		return hijackErr(errors.New("no suitable PDF files to merge"), r)
 	}
 	baseFilename, err := rand.Get()
 	if err != nil {
-		return fmt.Errorf("getting result file name: %v", err)
+		return hijackErr(fmt.Errorf("getting result file name: %v", err), r)
 	}
 	filename := fmt.Sprintf("%s.pdf", baseFilename)
 	fpath := fmt.Sprintf("%s/%s", r.dirPath, filename)
 	if r.webhookURL() == "" {
+		defer r.removeAll()
 		// if no webhook URL given, run merge
 		// and directly return the resulting PDF file
 		// or an error.
@@ -39,6 +43,7 @@ func merge(c echo.Context) error {
 	// run the following lines in a goroutine so that
 	// it doesn't block.
 	go func() {
+		defer r.removeAll()
 		if err := printer.Merge(fpaths, fpath); err != nil {
 			c.Logger().Errorf("%v", err)
 			return

internal/app/api/office.go

@@ -24,30 +24,29 @@ var officeExts = []string{
 func convertOffice(c echo.Context) error {
 	r, err := newResource(c)
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
-	defer r.removeAll()
 	ctx, cancel := newContext(r)
 	if cancel != nil {
 		defer cancel()
 	}
 	fpaths, err := r.filePaths(officeExts)
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	if len(fpaths) == 0 {
-		return errors.New("no suitable office documents to convert")
+		return hijackErr(errors.New("no suitable office documents to convert"), r)
 	}
 	p := &printer.Office{Context: ctx, FilePaths: fpaths}
 	paperSize, err := r.paperSize()
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	p.PaperWidth = paperSize[0]
 	p.PaperHeight = paperSize[1]
 	landscape, err := r.landscape()
 	if err != nil {
-		return err
+		return hijackErr(err, r)
 	}
 	p.Landscape = landscape
 	return print(c, p, r)

internal/app/api/resource.go

@@ -49,17 +49,17 @@ func newResource(c echo.Context) (*resource, error) {
 	r := &resource{values: v, dirPath: dirPath}
 	form, err := c.MultipartForm()
 	if err != nil {
-		return nil, fmt.Errorf("getting multipart form: %v", err)
+		return r, fmt.Errorf("getting multipart form: %v", err)
 	}
 	for _, files := range form.File {
 		for _, fh := range files {
 			in, err := fh.Open()
 			if err != nil {
-				return nil, fmt.Errorf("%s: opening file: %v", fh.Filename, err)
+				return r, fmt.Errorf("%s: opening file: %v", fh.Filename, err)
 			}
 			defer in.Close()
 			if err := r.writeFile(fh.Filename, in); err != nil {
-				return nil, err
+				return r, err
 			}
 		}
 	}