/_stats broken after closing index with alias

[brainsiq]

If an aliased index is closed then the _stats endpoint returns an error

curl http://localhost:9200/_stats

{"error":{"root_cause":[{"type":"index_closed_exception","reason":"closed","index":"test_index"}],"type":"index_closed_exception","reason":"closed","index":"test_index"},"status":403}

This does not happen if the alias is removed first. I think that this should not error, it should just exclude the closed index from the stats as normal?

[clintongormley]

Related to #15730 and #14982

[javanna]

Same as described in #15730 (comment) .

The exception returned by GET _stats has been resolved by #15882, given that not specifying indices is considered a wildcard expressions. GET _stats?expand_wildcards=open,closed does return an exception as the expand_wildcards option is honoured.

If you do specify an alias that points to some closed index, you get back an exception by default: GET alias/_stats but ignore_unavailable allows to control whether closed indices should be ignored or not: GET alias/_stats?ignore_unavailable=true doesn't return exception.

I think we can close this one, the actual bug was same as #13278 which was fixed by #15882 .