Refactor: fixing (potential) bugs around closing

app/preferences.go

@@ -64,19 +64,22 @@ func (p *preferences) load() {
 	}
 }
 
-func (p *preferences) loadFromFile(path string) error {
+func (p *preferences) loadFromFile(path string) (err error) {
 	file, err := os.Open(path) // #nosec
 	if err != nil {
 		if os.IsNotExist(err) {
-			err := os.MkdirAll(filepath.Dir(path), 0700)
-			if err != nil {
+			if err := os.MkdirAll(filepath.Dir(path), 0700); err != nil {
 				return err
 			}
 			return nil
 		}
 		return err
 	}
-	defer file.Close()
+	defer func() {
+		if r := file.Close(); r != nil {
+			err = r
+		}
+	}()
 	decode := json.NewDecoder(file)
 
 	p.InMemoryPreferences.WriteValues(func(values map[string]interface{}) {

cmd/fyne/internal/commands/bundle.go

@@ -138,35 +138,23 @@ func (b *Bundler) Run(args []string) {
 	}
 }
 
-func (b *Bundler) bundleAction(ctx *cli.Context) error {
+func (b *Bundler) bundleAction(ctx *cli.Context) (err error) {
 	if ctx.Args().Len() != 1 {
 		return errors.New("missing required file or directory parameter after flags")
 	}
 
 	outFile := os.Stdout
 	if b.out != "" {
-		fileModes := os.O_RDWR | os.O_CREATE | os.O_TRUNC
-		if b.noheader {
-			fileModes = os.O_RDWR | os.O_APPEND
+		file, closeFile, err := getOutputFile(b.out, b.noheader)
+		if err != nil {
+			return err
 		}
-
-		f, err := os.OpenFile(b.out, fileModes, 0666)
-		if err == nil {
-			outFile = f
-		} else {
-			if os.IsNotExist(err) {
-				f, err = os.Create(b.out)
-				if err == nil {
-					outFile = f
-				} else {
-					fyne.LogError("Unable to read, or create, output file : "+b.out, err)
-					return err
-				}
-			} else {
-				fyne.LogError("Unable to open output file", err)
-				return err
+		defer func() {
+			if r := closeFile(); r != nil {
+				err = r
 			}
-		}
+		}()
+		outFile = file
 	}
 
 	arg := ctx.Args().First()
@@ -227,6 +215,30 @@ func (b *Bundler) doBundle(filepath string, out *os.File) {
 	writeResource(filepath, b.name, out)
 }
 
+func getOutputFile(filePath string, noheader bool) (file *os.File, close func() error, err error) {
+	fileModes := os.O_RDWR | os.O_CREATE | os.O_TRUNC
+	if noheader {
+		fileModes = os.O_RDWR | os.O_APPEND
+	}
+
+	f, err := os.OpenFile(filePath, fileModes, 0666)
+	if err != nil {
+		if !os.IsNotExist(err) {
+			fyne.LogError("Unable to open output file", err)
+			return nil, nil, err
+		}
+
+		// try creating the file
+		f, err = os.Create(filePath)
+		if err != nil {
+			fyne.LogError("Unable to read, or create, output file : "+filePath, err)
+			return nil, nil, err
+		}
+	}
+
+	return f, f.Close, nil
+}
+
 func sanitiseName(file, prefix string) string {
 	titled := strings.Title(file)
 

cmd/fyne/internal/commands/package-darwin.go

@@ -20,25 +20,31 @@ type darwinData struct {
 	Category      string
 }
 
-func (p *Packager) packageDarwin() error {
+func (p *Packager) packageDarwin() (err error) {
 	appDir := util.EnsureSubDir(p.dir, p.name+".app")
 	exeName := filepath.Base(p.exe)
 
 	contentsDir := util.EnsureSubDir(appDir, "Contents")
 	info := filepath.Join(contentsDir, "Info.plist")
-	infoFile, _ := os.Create(info)
+	infoFile, err := os.Create(info)
+	if err != nil {
+		return errors.Wrap(err, "Failed to write plist template")
+	}
+	defer func() {
+		if r := infoFile.Close(); r != nil {
+			err = r
+		}
+	}()
 
 	tplData := darwinData{Name: p.name, ExeName: exeName, AppID: p.appID, Version: p.appVersion, Build: p.appBuild,
 		Category: strings.ToLower(p.category)}
-	err := templates.InfoPlistDarwin.Execute(infoFile, tplData)
-	if err != nil {
+	if err := templates.InfoPlistDarwin.Execute(infoFile, tplData); err != nil {
 		return errors.Wrap(err, "Failed to write plist template")
 	}
 
 	macOSDir := util.EnsureSubDir(contentsDir, "MacOS")
 	binName := filepath.Join(macOSDir, exeName)
-	err = util.CopyExeFile(p.exe, binName)
-	if err != nil {
+	if err := util.CopyExeFile(p.exe, binName); err != nil {
 		return errors.Wrap(err, "Failed to copy exe file")
 	}
 
@@ -58,7 +64,11 @@ func (p *Packager) packageDarwin() error {
 	if err != nil {
 		return errors.Wrap(err, "Failed to open destination file")
 	}
-	defer dest.Close()
+	defer func() {
+		if r := dest.Close(); r != nil {
+			err = r
+		}
+	}()
 	if err := icns.Encode(dest, srcImg); err != nil {
 		return errors.Wrap(err, "Failed to encode icns")
 	}

cmd/fyne/internal/commands/release.go

@@ -8,6 +8,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strings"
+	"text/template"
 
 	"fyne.io/fyne/v2"
 	"fyne.io/fyne/v2/cmd/fyne/internal/mobile"
@@ -260,23 +261,22 @@ func (r *Releaser) packageIOSRelease() error {
 	}
 
 	payload := filepath.Join(r.dir, "Payload")
-	os.Mkdir(payload, 0750)
+	_ = os.Mkdir(payload, 0750)
 	defer os.RemoveAll(payload)
 	appName := mobile.AppOutputName(r.os, r.name)
 	payloadAppDir := filepath.Join(payload, appName)
-	os.Rename(filepath.Join(r.dir, appName), payloadAppDir)
+	if err := os.Rename(filepath.Join(r.dir, appName), payloadAppDir); err != nil {
+		return err
+	}
 
-	entitlementPath := filepath.Join(r.dir, "entitlements.plist")
-	entitlements, _ := os.Create(entitlementPath)
-	entitlementData := struct{ TeamID, AppID string }{
+	cleanup, err := r.writeEntitlements(templates.EntitlementsDarwinMobile, struct{ TeamID, AppID string }{
 		TeamID: team,
 		AppID:  r.appID,
-	}
-	err = templates.EntitlementsDarwinMobile.Execute(entitlements, entitlementData)
-	entitlements.Close()
+	})
 	if err != nil {
 		return errors.New("failed to write entitlements plist template")
 	}
+	defer cleanup()
 
 	cmd := exec.Command("codesign", "-f", "-vv", "-s", r.certificate, "--entitlements",
 		"entitlements.plist", "Payload/"+appName+"/")
@@ -297,14 +297,12 @@ func (r *Releaser) packageMacOSRelease() error {
 	unsignedPath := r.name + "-unsigned.pkg"
 
 	defer os.RemoveAll(r.name + ".app") // this was the output of package and it can get in the way of future builds
-	entitlementPath := filepath.Join(r.dir, "entitlements.plist")
-	entitlements, _ := os.Create(entitlementPath)
-	err := templates.EntitlementsDarwin.Execute(entitlements, nil)
-	entitlements.Close()
+
+	cleanup, err := r.writeEntitlements(templates.EntitlementsDarwin, nil)
 	if err != nil {
 		return errors.New("failed to write entitlements plist template")
 	}
-	defer os.Remove(entitlementPath)
+	defer cleanup()
 
 	cmd := exec.Command("codesign", "-vfs", appCert, "--entitlement", "entitlements.plist", r.name+".app")
 	err = cmd.Run()
@@ -328,7 +326,7 @@ func (r *Releaser) packageMacOSRelease() error {
 
 func (r *Releaser) packageWindowsRelease(outFile string) error {
 	payload := filepath.Join(r.dir, "Payload")
-	os.Mkdir(payload, 0750)
+	_ = os.Mkdir(payload, 0750)
 	defer os.RemoveAll(payload)
 
 	manifestPath := filepath.Join(payload, "appxmanifest.xml")
@@ -447,6 +445,26 @@ func (r *Releaser) validate() error {
 	return nil
 }
 
+func (r *Releaser) writeEntitlements(tmpl *template.Template, entitlementData interface{}) (cleanup func(), err error) {
+	entitlementPath := filepath.Join(r.dir, "entitlements.plist")
+	entitlements, err := os.Create(entitlementPath)
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		if r := entitlements.Close(); r != nil {
+			err = r
+		}
+	}()
+
+	if err := tmpl.Execute(entitlements, entitlementData); err != nil {
+		return nil, err
+	}
+	return func() {
+		_ = os.Remove(entitlementPath)
+	}, nil
+}
+
 func (r *Releaser) zipAlign(path string) error {
 	unaligned := filepath.Join(filepath.Dir(path), "unaligned.apk")
 	err := os.Rename(path, unaligned)

cmd/fyne/internal/util/file.go

@@ -39,9 +39,8 @@ func EnsureSubDir(parent, name string) string {
 	return path
 }
 
-func copyFileMode(src, tgt string, perm os.FileMode) error {
-	_, err := os.Stat(src)
-	if err != nil {
+func copyFileMode(src, tgt string, perm os.FileMode) (err error) {
+	if _, err := os.Stat(src); err != nil {
 		return err
 	}
 
@@ -55,7 +54,11 @@ func copyFileMode(src, tgt string, perm os.FileMode) error {
 	if err != nil {
 		return err
 	}
-	defer target.Close()
+	defer func() {
+		if r := target.Close(); r != nil {
+			err = r
+		}
+	}()
 
 	_, err = io.Copy(target, source)
 	return err

resource.go

@@ -63,6 +63,7 @@ func LoadResourceFromURLString(urlStr string) (Resource, error) {
 	if err != nil {
 		return nil, err
 	}
+	defer res.Body.Close()
 
 	bytes, err := ioutil.ReadAll(res.Body)
 	if err != nil {