Improve error
diff --git a/go/pkg/cas/upload.go b/go/pkg/cas/upload.go
index f3b1d5b..d867ed5 100644
--- a/go/pkg/cas/upload.go
+++ b/go/pkg/cas/upload.go
@@ -106,13 +106,19 @@
digest *repb.Digest // may be nil, e.g. for dangling symlinks
}
-// ErrSkip when returned by UploadOptions.Prelude, means the file/dir must be
-// not be uploaded.
-//
-// Note that if UploadOptions.PreserveSymlinks is true and the ErrSkip is
-// returned for a symlink target, but not the symlink itself, then it may
-// result in a dangling symlink.
-var ErrSkip = errors.New("skip file")
+var (
+ // ErrSkip when returned by UploadOptions.Prelude, means the file/dir must be
+ // not be uploaded.
+ //
+ // Note that if UploadOptions.PreserveSymlinks is true and the ErrSkip is
+ // returned for a symlink target, but not the symlink itself, then it may
+ // result in a dangling symlink.
+ ErrSkip = errors.New("skip file")
+
+ // ErrNoDigest indicates that the requested digest is uknown.
+ // Use errors.Is instead of direct equality check.
+ ErrNoDigest = errors.New("the requested digest is unknown")
+)
// UploadResult is the result of a Client.Upload call.
// It provides file/dir digests and statistics.
@@ -121,9 +127,6 @@
u *uploader
}
-// ErrNoDigest indicates that the requested digest is uknown.
-var ErrNoDigest = errors.New("the requested digest is unknown")
-
// Digest returns the digest computed for a file/dir at ps.Path.
//
// To retrieve a digest of a regular file, only ps.Path is checked - other
@@ -132,7 +135,8 @@
// To retrieve a digest of a directory or a symlink, ps.Exclude must match one
// of the PathSpecs passed to Client.Upload earlier.
//
-// If the digest is unknown, returns (nil, nil).
+// If the digest is unknown, returns (nil, err), where err is ErrDigestUnknown
+// according to errors.Is.
// If the file is a danging symlink, then its digest is unknown.
func (r *UploadResult) Digest(ps *PathSpec) (digest.Digest, error) {
if !filepath.IsAbs(ps.Path) {
@@ -148,7 +152,7 @@
key := makeFSCacheKey(ps.Path, info.Mode(), ps.Exclude)
switch val, err, loaded := r.u.fsCache.Load(key); {
case !loaded:
- return digest.Digest{}, ErrNoDigest
+ return digest.Digest{}, errors.Wrapf(ErrNoDigest, "digest not found for %#v", ps)
case err != nil:
return digest.Digest{}, err
default:
