Discord.js snippets for diffing changes of Discord permission overwrites

diff-permission-overwrites.md

These are two potential scripts for computing (sane) diffs of permission overwrite changes on Discord channels with Discord.js.

discord-js-permission-overwrite-diffs-new.js

bot.on('channelUpdate', (oldChannel, newChannel) => {
    if (!oldChannel.guild) {
        return
    }

    // get all roles/members that did or did not have overwrites:
    const overwriteChanges = [...oldChannel.permissionOverwrites.keyArray(), ...newChannel.permissionOverwrites.keyArray()]
        // filter out duplicate role/member IDs
        .reduce((out, next) => out.includes(next) ? out : out.concat(next), [])
        // map to pairs
        .map(id => ({ id, before: oldChannel.permissionOverwrites.get(id), after: newChannel.permissionOverwrites.get(id) }))
        // convert the PermissionOverwrites objects into easier to deal with null-safe types
        .map(({ id, before, after }) => ({
            id,
            // get the overwrite type (role or member) from whichever object exists
            type: before ? before.type : after.type,
            before: {
                // instead of having potentially null values for before/after, just use an empty array
                allow: before ? before.allow.toArray() : [],
                deny: before ? before.deny.toArray() : []
            },
            after: {
                allow: after ? after.allow.toArray() : [],
                deny: after ? after.deny.toArray() : []
            }
        }))
        // find diffs
        .map(({ id, type, before, after }) => ({
            // preserve the ID & type
            id,
            type,
            // compute permissions that are removed
            // if the permission overwrite for the user/role wasn't deleted (after), filter out things that still exist (weren't deleted)
            removed: [...before.allow, ...before.deny].filter(it => ![...after.allow, ...after.deny].includes(it)),
            // if there are permission overwrites for the user/role after the update, make sure that anything that previously existed was removed
            newlyAllowed: after.allow.filter(it => !before.allow.includes(it)),
            newlyDenied: after.deny.filter(it => !before.deny.includes(it))
        }))
        // filter to only overwrites that changed in some way
        .filter(({ removed, newlyAllowed, newlyDenied }) => removed.length || newlyAllowed.length || newlyDenied.length)

    if (overwriteChanges.length < 1) {
        // no changes happened to permission in this channel update, so ignore
        return
    }

    // overwriteChanges is an array of permission overwrites that have changed, stored as objects in the format of:
    // {
    //     id: string - the id of the role/member that changed
    //     type: string - either 'role' or 'member'
    //     removed: string[] - any permissions that are no longer allowed/denied
    //     newlyAllowed: string[] - the newly allowed permissions
    //     newlyDenied: string[] - the newly denied permissions
    // }

    console.log(`Received channel permission update for #${oldChannel.name} in ${oldChannel.guild.name}:`)
    overwriteChanges.forEach(overwrite => console.log(overwrite))
});

discord-js-permission-overwrite-diffs.js

bot.on('channelUpdate', (oldChannel, newChannel) => {
    if (!oldChannel.guild) {
        return
    }

    // get all roles/members that did or did not have overwrites:
    const overwriteChanges = [...oldChannel.permissionOverwrites.keyArray(), ...newChannel.permissionOverwrites.keyArray()]
        // filter out duplicate role/member IDs
        .reduce((out, next) => out.includes(next) ? out : out.concat(next), [])
        // map to pairs
        .map(id => ({ id, before: oldChannel.permissionOverwrites.get(id), after: newChannel.permissionOverwrites.get(id) }))
        // find diffs
        .map(({ id, before, after }) => ({
            // preserve the ID
            id,
            // get the overwrite type (role or member) from whichever object exists
            type: before ? before.type : after.type,
            removed: !before ? [] : [...before.allow.toArray(), ...before.deny.toArray()]
                // if the permission overwrite for the user/role wasn't deleted (after), filter out things that still exist (weren't deleted)
                .filter(it => after ? ![...after.allow.toArray(), ...after.deny.toArray()].includes(it) : true),
            // if there are permission overwrites for the user/role after the update, make sure that anything that previously existed was removed
            newlyAllowed: !after ? [] : (before ? after.allow.remove(before.allow) : after.allow).toArray(),
            newlyDenied: !after ? [] : (before ? after.deny.remove(before.deny) : after.deny).toArray()
        }))
        // filter to only overwrites that changed in some way
        .filter(({ removed, newlyAllowed, newlyDenied }) => removed.length || newlyAllowed.length || newlyDenied.length)

    if (overwriteChanges.length < 1) {
        // no changes happened to permission in this channel update, so ignore
        return
    }
    
    // overwriteChanges is an array of permission overwrites that have changed, stored as objects in the format of:
    // {
    //     id: string - the id of the role/member that changed
    //     type: string - either 'role' or 'member'
    //     removed: string[] - any permissions that are no longer allowed/denied
    //     newlyAllowed: string[] - the newly allowed permissions
    //     newlyDenied: string[] - the newly denied permissions
    // }

    console.log(`Received channel permission update for #${oldChannel.name} in ${oldChannel.guild.name}:`)
    overwriteChanges.forEach(overwrite => console.log(overwrite))
});