From 1e66d052fd50be46d3b0dc2482bc5ef2868befe4 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Fri, 6 May 2022 12:06:20 +0100
Subject: [PATCH] fs: fix FixRangeOption to make fetch to end Range options
 absolute

Before this change FixRangeOption was leaving `Range: bytes=21-`
alone, thus not fulfilling its contract of making Range requests
absolute.

As it happens this form isn't supported by Cloudflare R2.

After this change the request is normalised to `Range: bytes=21-25`.

See: #5642
---
 fs/open_options.go      | 3 ++-
 fs/open_options_test.go | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/open_options.go b/fs/open_options.go
index 8d997118a..268024b17 100644
--- a/fs/open_options.go
+++ b/fs/open_options.go
@@ -158,7 +158,8 @@ func FixRangeOption(options []OpenOption, size int64) {
 				x = &RangeOption{Start: size - x.End, End: -1}
 				options[i] = x
 			}
-			if x.End > size {
+			// If end is too big or undefined, fetch to the end
+			if x.End > size || x.End < 0 {
 				x = &RangeOption{Start: x.Start, End: size - 1}
 				options[i] = x
 			}
diff --git a/fs/open_options_test.go b/fs/open_options_test.go
index 52fc42ddb..6327a8c9e 100644
--- a/fs/open_options_test.go
+++ b/fs/open_options_test.go
@@ -183,7 +183,7 @@ func TestFixRangeOptions(t *testing.T) {
 				&RangeOption{Start: 1, End: -1},
 			},
 			want: []OpenOption{
-				&RangeOption{Start: 1, End: -1},
+				&RangeOption{Start: 1, End: 99},
 			},
 			size: 100,
 		},
@@ -193,7 +193,7 @@ func TestFixRangeOptions(t *testing.T) {
 				&RangeOption{Start: -1, End: 10},
 			},
 			want: []OpenOption{
-				&RangeOption{Start: 90, End: -1},
+				&RangeOption{Start: 90, End: 99},
 			},
 			size: 100,
 		},