From 14cab0fff0948fa243a1331bd7c1041aadc2c6ec Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Mon, 4 May 2020 12:17:46 +0100
Subject: [PATCH] local: fix "file not found" errors on post transfer Hash
 calculation

Before this change the local backend was returning file not found
errors for post transfer hashes for files which were moved. This was
caused by the routine which checks for the object being changed.

After this change we ignore file not found errors while checking to
see if the object has changed. If the hash has to be computed then a
file not found error will be thrown when it is opened, otherwise the
cached hash will be returned.
---
 backend/local/local.go | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/backend/local/local.go b/backend/local/local.go
index 126edd4d0..bcd6d9b68 100644
--- a/backend/local/local.go
+++ b/backend/local/local.go
@@ -768,8 +768,17 @@ func (o *Object) Hash(ctx context.Context, r hash.Type) (string, error) {
 	oldtime := o.modTime
 	oldsize := o.size
 	err := o.lstat()
+	var changed bool
 	if err != nil {
-		return "", errors.Wrap(err, "hash: failed to stat")
+		if os.IsNotExist(errors.Cause(err)) {
+			// If file not found then we assume any accumulated
+			// hashes are OK - this will error on Open
+			changed = true
+		} else {
+			return "", errors.Wrap(err, "hash: failed to stat")
+		}
+	} else {
+		changed = !o.modTime.Equal(oldtime) || oldsize != o.size
 	}
 
 	o.fs.objectHashesMu.Lock()
@@ -777,7 +786,7 @@ func (o *Object) Hash(ctx context.Context, r hash.Type) (string, error) {
 	hashValue, hashFound := o.hashes[r]
 	o.fs.objectHashesMu.Unlock()
 
-	if !o.modTime.Equal(oldtime) || oldsize != o.size || hashes == nil || !hashFound {
+	if changed || hashes == nil || !hashFound {
 		var in io.ReadCloser
 
 		if !o.translatedLink {