Crash due to index of of range in JSON encoder

[lammel]

We are seeing application crashes due to an error which seems to be caused by zerolog.

panic: runtime error: index out of range [-1]

goroutine 15 [running]:
github.com/rs/zerolog/internal/json.Encoder.AppendKey(...)
        /home/rl/.go/pkg/mod/github.com/rs/zerolog@v1.19.0/internal/json/base.go:7
github.com/rs/zerolog.(*Event).Str(0xc0000ae300, 0xac8fb3, 0x5, 0xac8ed2, 0x5, 0xc00008d9d8)
        /home/rl/.go/pkg/mod/github.com/rs/zerolog@v1.19.0/event.go:226 +0x1c2
github.com/rs/zerolog.(*Logger).newEvent(0xfe48a0, 0xc00069c000, 0x0, 0x4)
        /home/rl/.go/pkg/mod/github.com/rs/zerolog@v1.19.0/log.go:420 +0x32d
github.com/rs/zerolog.(*Logger).Debug(...)
        /home/rl/.go/pkg/mod/github.com/rs/zerolog@v1.19.0/log.go:293
github.com/rs/zerolog/log.Debug(...)
        /home/rl/.go/pkg/mod/github.com/rs/zerolog@v1.19.0/log/log.go:59
neotel.at/api/pcr-api/poller.pollEnterprises(0xc000284300, 0x0)
        /home/rl/work/pcr-api/poller/poller.go:85 +0xc3

In internal/json/base.go an array access might become out of range as:

func (e Encoder) AppendKey(dst []byte, key string) []byte {
	if dst[len(dst)-1] != '{' {
		dst = append(dst, ',')
	}
	return append(e.AppendString(dst, key), ':')
}

This could probably be fixed by using:

	if len(dst) > 0 && dst[len(dst)-1] != '{' {

But the issue might be something else, as we are logging quite data over the day and the crashed occur only around once a day.

[lammel]

Actually it seems the issue was introduced with commit 14dcf38 which removed the check for the length of the array to make it inlineable. This can cause the index out of range now in case the array is empty.

I'd suggest to readd the guard or see if there is a safe way to inline, without trading safety.

[lammel]

This issue is a duplicate of issue #239 which was fixed with PR #244.
Closing.