Bug report criteria

• This bug report is not security related, security issues should be disclosed privately via etcd maintainers.
• This is not a support request or question, support requests or questions should be raised in the etcd discussion forums.
• You have read the etcd bug reporting guidelines.
• Existing open issues along with etcd frequently asked questions have been checked and this is not a duplicate.

What happened?

I ran etcdctl member add -w json --hex=true, with the aim of extracting the newly added member ID for use with etcdctl member promote later. However, the member ID was printed as decimal:

> etcdctl member add test-node --peer-urls=https://10.16.36.111:2380 --learner=true -w json --hex=true
{"header":{"cluster_id":8614491861582198852,"member_id":9202843606982955899,"raft_term":2},"member":{"ID":12981492951526344977,"peerURLs":["https://10.16.36.111:2380"],"isLearner":true},"members":[{"ID":677637297205855628,"name":"etcd-i-0287724fa565aba47","peerURLs":["https://10.16.43.142:2380"],"clientURLs":["https://10.16.43.142:2379"]},{"ID":9202843606982955899,"name":"etcd-i-0a11bcfc6be104246","peerURLs":["https://10.16.33.50:2380"],"clientURLs":["https://10.16.33.50:2379"]},{"ID":12981492951526344977,"peerURLs":["https://10.16.36.111:2380"],"isLearner":true},{"ID":16455373321881049425,"name":"etcd-i-0e6aa2e540fd3c248","peerURLs":["https://10.16.36.53:2380"],"clientURLs":["https://10.16.36.53:2379"]}]

This does not match the behaviour of etcdctl member list -w json --hex=true, which prints the member IDs in hexadecimal, compatible for use with other etcdctl commands.

What did you expect to happen?

I expect etcdctl member add ... -w json --hex=true to print the IDs in hexadecimal, just like etcdctl member list does.

How can we reproduce it (as minimally and precisely as possible)?

Run the following command (the new member doesn't actually ever have to join the cluster, it can be immediately deleted afterwards):

etcdctl member add test-node --peer-urls=https://10.16.36.111:2380 --learner=true -w json --hex=true

Anything else we need to know?

No response

Etcd version (please run commands below)

$ etcd --version
etcd Version: 3.5.15
Git SHA: 9a5533382
Go Version: go1.21.12
Go OS/Arch: linux/arm64

$ etcdctl version
etcdctl version: 3.5.15
API version: 3.5

Etcd configuration (command line flags or environment variables)

Etcd debug information (please run commands below, feel free to obfuscate the IP address or FQDN in the output)

$ etcdctl member list -w table
# paste output here

$ etcdctl --endpoints=<member list> endpoint status -w table
# paste output here

Relevant log output