embed: guarantee the returned file of FS.Open implements io.Seeker

Fixes #45745 Change-Id: Ib49a9605a38074f544a5d28116862e191cea8c0f Reviewed-on: https://go-review.googlesource.com/c/go/+/313352 Run-TryBot: Hajime Hoshi <hajimehoshi@gmail.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org> Trust: Than McIntosh <thanm@google.com>
golang · Sep 10, 2021 · 90c5660 · 90c5660
1 parent c69f5c0
commit 90c5660
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/src/embed/embed.go b/src/embed/embed.go
@@ -291,6 +291,8 @@ func (f FS) readDir(dir string) []file {
 }
 
 // Open opens the named file for reading and returns it as an fs.File.
+//
+// The returned file implements io.Seeker when the file is not a directory.
 func (f FS) Open(name string) (fs.File, error) {
 	file := f.lookup(name)
 	if file == nil {
@@ -338,6 +340,10 @@ type openFile struct {
 	offset int64 // current read offset
 }
 
+var (
+	_ io.Seeker = (*openFile)(nil)
+)
+
 func (f *openFile) Close() error               { return nil }
 func (f *openFile) Stat() (fs.FileInfo, error) { return f.f, nil }