Less repetitive error messages in internal/cache

Many instances of errors.Wrap in this package would produce messages
like "Open: open <filename>: no such file or directory"; those now omit
the first "Open:" (or "Stat:", or "MkdirAll"). The function readVersion
now appends its own name to the error message, rather than the function
that failed, to make it easier to spot. Other function names (e.g.,
Load) are already added further up in the call chain.

internal/cache/cache.go

@@ -33,12 +33,12 @@ func readVersion(dir string) (v uint, err error) {
 	}
 
 	if err != nil {
-		return 0, errors.Wrap(err, "ReadFile")
+		return 0, errors.Wrap(err, "readVersion")
 	}
 
 	ver, err := strconv.ParseUint(string(buf), 10, 32)
 	if err != nil {
-		return 0, errors.Wrap(err, "ParseUint")
+		return 0, errors.Wrap(err, "readVersion")
 	}
 
 	return uint(ver), nil
@@ -56,13 +56,13 @@ const cachedirTagSignature = "Signature: 8a477f597d28d172789f06886806bc55\n"
 
 func writeCachedirTag(dir string) error {
 	if err := fs.MkdirAll(dir, dirMode); err != nil {
-		return err
+		return errors.WithStack(err)
 	}
 
 	tagfile := filepath.Join(dir, "CACHEDIR.TAG")
 	_, err := fs.Lstat(tagfile)
 	if err != nil && !os.IsNotExist(err) {
-		return errors.Wrap(err, "Lstat")
+		return errors.WithStack(err)
 	}
 
 	f, err := fs.OpenFile(tagfile, os.O_CREATE|os.O_EXCL|os.O_WRONLY, fileMode)
@@ -71,16 +71,16 @@ func writeCachedirTag(dir string) error {
 			return nil
 		}
 
-		return errors.Wrap(err, "OpenFile")
+		return errors.WithStack(err)
 	}
 
 	debug.Log("Create CACHEDIR.TAG at %v", dir)
 	if _, err := f.Write([]byte(cachedirTagSignature)); err != nil {
 		_ = f.Close()
-		return errors.Wrap(err, "Write")
+		return errors.WithStack(err)
 	}
 
-	return f.Close()
+	return errors.WithStack(f.Close())
 }
 
 // New returns a new cache for the repo ID at basedir. If basedir is the empty
@@ -98,7 +98,7 @@ func New(id string, basedir string) (c *Cache, err error) {
 
 	err = fs.MkdirAll(basedir, 0700)
 	if err != nil {
-		return nil, err
+		return nil, errors.WithStack(err)
 	}
 
 	// create base dir and tag it as a cache directory
@@ -124,7 +124,7 @@ func New(id string, basedir string) (c *Cache, err error) {
 	if os.IsNotExist(err) {
 		err = fs.MkdirAll(cachedir, dirMode)
 		if err != nil {
-			return nil, err
+			return nil, errors.WithStack(err)
 		}
 		created = true
 	}
@@ -138,13 +138,13 @@ func New(id string, basedir string) (c *Cache, err error) {
 	if v < cacheVersion {
 		err = ioutil.WriteFile(filepath.Join(cachedir, "version"), []byte(fmt.Sprintf("%d", cacheVersion)), fileMode)
 		if err != nil {
-			return nil, errors.Wrap(err, "WriteFile")
+			return nil, errors.WithStack(err)
 		}
 	}
 
 	for _, p := range cacheLayoutPaths {
 		if err = fs.MkdirAll(filepath.Join(cachedir, p), dirMode); err != nil {
-			return nil, err
+			return nil, errors.WithStack(err)
 		}
 	}
 

internal/cache/file.go

@@ -48,13 +48,13 @@ func (c *Cache) load(h restic.Handle, length int, offset int64) (io.ReadCloser,
 
 	f, err := fs.Open(c.filename(h))
 	if err != nil {
-		return nil, errors.Wrap(err, "Open")
+		return nil, errors.WithStack(err)
 	}
 
 	fi, err := f.Stat()
 	if err != nil {
 		_ = f.Close()
-		return nil, errors.Wrap(err, "Stat")
+		return nil, errors.WithStack(err)
 	}
 
 	if fi.Size() <= crypto.Extension {
@@ -94,15 +94,11 @@ func (c *Cache) saveWriter(h restic.Handle) (io.WriteCloser, error) {
 	p := c.filename(h)
 	err := fs.MkdirAll(filepath.Dir(p), 0700)
 	if err != nil {
-		return nil, errors.Wrap(err, "MkdirAll")
+		return nil, errors.WithStack(err)
 	}
 
 	f, err := fs.OpenFile(p, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0400)
-	if err != nil {
+	return f, errors.WithStack(err)
-		return nil, errors.Wrap(err, "Create")
-	}
-
-	return f, err
 }
 
 // Save saves a file in the cache.
@@ -133,7 +129,7 @@ func (c *Cache) Save(h restic.Handle, rd io.Reader) error {
 
 	if err = f.Close(); err != nil {
 		_ = c.remove(h)
-		return errors.Wrap(err, "Close")
+		return errors.WithStack(err)
 	}
 
 	return nil