GuildMember.nickname has incorrect typings

[octylFractal]

Please describe the problem you are having in as much detail as possible:
I am trying to avoid saving a nickname if it is not set, but the typings incorrectly claim string | null when it is actually string | undefined.

Include a reproducible code sample here, if possible:

    const nickname = member.nickname;
    if (nickname !== null) {
        console.log(memTag, 'Saving name:', nickname);
        setUserName(member.user.id, member.guild.id, nickname);
    }

This code will log "Saving name: undefined" when someone has no nickname, rather than not logging a message at all.

Further details:

• discord.js version: 12.2.0
• Node.js version: 14.1.0
• Operating system: Linux
• Priority this issue should have – please be realistic and elaborate if possible: High priority, causes unexpected bugs due to undeclared branch possibilities that the compiler cannot know

• I have also tested the issue on latest master, commit hash: f9f3661

[almostSouji]

"member" seems to not refer to a GuildMember instance then.

We receive a member presence from discord in the form

{
  user: [Object],
  roles: [Array],
  nick: null,
  premium_since: null,
  mute: false,
  deaf: false,
  joined_at: '2017-08-10T23:07:00.313000+00:00'
}

If there is no nickname this property will be null

discord.js/src/structures/GuildMember.js

Line 79 in d827544

if (typeof data.nick !== 'undefined') this.nickname = data.nick;

This check updates the members nickname, if it's not undefined (undefined meaning it's not present in the update data, discord only sends partial data on updates). In the initial payload it will be null, null is not undefined so will get initialized with null

Edit: If the nickname is removed the data will have null as well!

---

• User (e.g. <Message>.author): global discord user (avatar, username, tag)
• GuildMember (e.g. <Message>.member): user data associated with a specific server (guild, nickname, roles, permissions, voice channel, etc.)
• converting User to GuildMember: you need to fetch it from the guild you need the information for (<Guild>.members.fetch(<User>))
• converting GuildMember to User: <GuildMember>.user

[octylFractal]

I'm not sure how that could be possible ("member" seems to not refer to a GuildMember instance then), here is how I fetch the member:

async function onJoinGuild(guild: Guild) {
    console.log('Joined guild', guild.name, `(${guild.id})`);
    const members = await guild.members.fetch();
    members.forEach(m => {
        console.log("Nickname", m.nickname);
    });
}

With this, I still log undefined nicknames. Do you mean to tell me that the fetch() method also has incorrect typing?

[almostSouji]

I guess i was a bit quick to dismiss this, i feel reminded of #4593 where we had undefined for NSFW channels and can indeed reproduce having both undefined and null nicknames on servers. We will look further into causes and remedies available.

[almostSouji]

This is not a matter of incorrect typings but a bug of the library not handling the initial data correctly. The field is simply not present (access will return undefined) if the member in question has no nick name, causing this value to be inserted. The wanted, documented and typed behavior is null.