misc.Exists: bubble up any unexpected errors

Fixes https://gitlab.com/postmarketOS/postmarketos-mkinitfs/-/issues/6

cmd/mkinitfs/main.go

@@ -48,9 +48,12 @@ func main() {
 	}
 
 	deviceinfoFile := "/etc/deviceinfo"
-	if !misc.Exists(deviceinfoFile) {
+	if exists, err := misc.Exists(deviceinfoFile); !exists {
 		log.Printf("NOTE: %q not found, this file is required by mkinitfs.\n", deviceinfoFile)
 		return
+	} else if err != nil {
+		retCode = 1
+		log.Printf("received unexpected error when getting status for %q: %s", deviceinfoFile, err)
 	}
 
 	devinfo, err := deviceinfo.ReadDeviceinfo(deviceinfoFile)

internal/filelist/modules/modules.go

@@ -40,10 +40,12 @@ func (m *Modules) List() (*filelist.FileList, error) {
 	files := filelist.NewFileList()
 
 	modDir := filepath.Join("/lib/modules", kernVer)
-	if !misc.Exists(modDir) {
+	if exists, err := misc.Exists(modDir); !exists {
 		// dir /lib/modules/<kernel> if kernel built without module support, so just print a message
 		log.Printf("-- kernel module directory not found: %q, not including modules", modDir)
 		return files, nil
+	} else if err != nil {
+		return nil, fmt.Errorf("received unexpected error when getting status for %q: %w", modDir, err)
 	}
 
 	// modules.* required by modprobe
@@ -148,8 +150,10 @@ func getModulesInDir(modPath string) (files []string, err error) {
 func getModule(modName string, modDir string) (files []string, err error) {
 
 	modDep := filepath.Join(modDir, "modules.dep")
-	if !misc.Exists(modDep) {
+	if exists, err := misc.Exists(modDep); !exists {
 		return nil, fmt.Errorf("kernel module.dep not found: %s", modDir)
+	} else if err != nil {
+		return nil, fmt.Errorf("received unexpected error when getting module.dep status: %w", err)
 	}
 
 	fd, err := os.Open(modDep)
@@ -165,9 +169,12 @@ func getModule(modName string, modDir string) (files []string, err error) {
 
 	for _, dep := range deps {
 		p := filepath.Join(modDir, dep)
-		if !misc.Exists(p) {
+		if exists, err := misc.Exists(p); !exists {
 			return nil, fmt.Errorf("tried to include a module that doesn't exist in the modules directory (%s): %s", modDir, p)
+		} else if err != nil {
+			return nil, fmt.Errorf("received unexpected error when getting status for %q: %w", p, err)
 		}
+
 		files = append(files, p)
 	}
 

internal/filelist/osksdl/osksdl.go

@@ -28,8 +28,11 @@ func New(mesaDriverName string) *OskSdl {
 // disk (d)encryption
 func (s *OskSdl) List() (*filelist.FileList, error) {
 	files := filelist.NewFileList()
-	if !misc.Exists("/usr/bin/osk-sdl") {
+
+	if exists, err := misc.Exists("/usr/bin/osk-sdl"); !exists {
 		return files, nil
+	} else if err != nil {
+		return files, fmt.Errorf("received unexpected error when getting status for %q: %w", "/usr/bin/osk-sdl", err)
 	}
 
 	log.Println("- Including osk-sdl support")
@@ -145,8 +148,10 @@ func getOskConfFontPath(oskConfPath string) (string, error) {
 			path = fields[2]
 		}
 	}
-	if !misc.Exists(path) {
+	if exists, err := misc.Exists(path); !exists {
 		return path, fmt.Errorf("unable to find font: %s", path)
+	} else if err != nil {
+		return path, fmt.Errorf("received unexpected error when getting status for %q: %w", path, err)
 	}
 
 	return path, nil

internal/misc/misc.go

@@ -4,6 +4,7 @@
 package misc
 
 import (
+	"errors"
 	"log"
 	"os"
 	"time"
@@ -47,10 +48,18 @@ func TimeFunc(start time.Time, name string) {
 	log.Printf("%s completed in: %s", name, elapsed)
 }
 
-// Exists tests if the given file/dir exists or not
-func Exists(file string) bool {
-	if _, err := os.Stat(file); err == nil {
-		return true
+// Exists tests if the given file/dir exists or not. Returns any errors related
+// to os.Stat if the type is *not* ErrNotExist. If an error is returned, then
+// the value of the returned boolean cannot be trusted.
+func Exists(file string) (bool, error) {
+	_, err := os.Stat(file)
+	if err == nil {
+		return true, nil
+	} else if errors.Is(err, os.ErrNotExist) {
+		// Don't return the error, the file doesn't exist which is OK
+		return false, nil
 	}
-	return false
+
+	// Other errors from os.Stat returned here
+	return false, err
 }