feed.go:21: index out of range [0] with length 0

It seems one of my feeds returns nothing and so triggers a panic because of a missing length check in src/parser/feed.go:21.

panic: runtime error: index out of range [0] with length 0

goroutine 343937 [running]:
github.com/nkanaev/yarr/src/parser.sniff(0xc00016f7ba, 0x2, 0x2, 0xc00016f7ba, 0x2)
        github.com/nkanaev/yarr/src/parser/feed.go:21 +0x390
github.com/nkanaev/yarr/src/parser.Parse(0x3da0c0, 0xc00049ff80, 0xc000642d80, 0x18, 0x3da440)
        github.com/nkanaev/yarr/src/parser/feed.go:59 +0x245
github.com/nkanaev/yarr/src/worker.listItems(0x4c, 0xc0002f4318, 0xc000642030, 0x14, 0x0, 0x0, 0xc0003fc0a0, 0x1d, 0xc0000240f0, 0
x23, ...)
        github.com/nkanaev/yarr/src/worker/crawler.go:193 +0x385
github.com/nkanaev/yarr/src/worker.(*Worker).worker(0xc00007dd10, 0xc000361c80, 0xc00037a060)
        github.com/nkanaev/yarr/src/worker/worker.go:136 +0x145
created by github.com/nkanaev/yarr/src/worker.(*Worker).refresher
        github.com/nkanaev/yarr/src/worker/worker.go:117 +0xcf
2021/06/30 09:43:24 main.go:86: using db file /var/db/yarr/storage.db
2021/06/30 09:43:24 main.go:133: starting server at http://10.192.0.5:7070
2021/06/30 09:43:24 worker.go:105: Refreshing feeds
2021/06/30 09:43:24 worker.go:76: auto-refresh 30m: starting

I simply added a length check that fixes it for me.

--- src/parser/feed.go.orig 2021-06-07 09:07:20 UTC
+++ src/parser/feed.go
@@ -18,6 +18,11 @@ type processor func(r io.Reader) (*Feed, error)
 func sniff(lookup string) (string, processor) {
    lookup = strings.TrimSpace(lookup)
    lookup = strings.TrimLeft(lookup, "\x00\xEF\xBB\xBF\xFE\xFF")
+
+   if len(lookup) < 1 {
+       return "", nil
+   }
+
    switch lookup[0] {
    case '<':
        decoder := xmlDecoder(strings.NewReader(lookup))

nkanaev / yarr

feed.go:21: index out of range [0] with length 0 #69