Add filter point before group membership requests are saved

[dcavins]

We currently don't offer a way to prevent membership requests from being saved on a per-request basis. Say, for example, you want to add a required extended profile field, or you want to require that the "comments" field be completed before accepting the membership.

The attached patch adds a filter that fires immediately before the member is saved so that plugins can stop the process if necessary.

Please let me know if there's a smarter way to accomplish this.

[r-a-y]

I think we should add the bail condition to BP_Groups_Member::save().

Then you could manipulate the request object on the 'groups_member_before_save' hook. See bp_groups_member.patch for what I have in mind.

[dcavins]

Thanks for your comments, r-a-y!

I think that your pre-save bail condition makes perfect sense in BP_Groups_Member::save(), since it would be applicable to every group membership case.

I do wonder, though, about how easy it'd be for a beginner BP-er to find it and see how it could be used to stop a request from being created (like knowing how to identify membership requests vs invitations at the groups_member_before_save filter and that emptying the user_id would then torpedo the save).

Maybe there's value to adding both approaches--the covers-every-case bail condition and the really-obviously-named filter. :)

[r-a-y]

I do wonder, though, about how easy it'd be for a beginner BP-er to find it and see how it could be used to stop a request from being created (like knowing how to identify membership requests vs invitations at the groups_member_before_save filter and that emptying the user_id would then torpedo the save).

For sure! Let's do both.

[boonebgorges]

In 9999:

Bail out of saving a group membership if the group_id or user_id props are not set.

In addition to basic validation, this also provides a roundabout way for
developers to noop a membership save at the 'group_member_before_save' hook.

Props r-a-y.
See #6524.

[DJPaul]

@dcavins is there more to do here?

[dcavins]

@djpaul: Yes, I'd like to do more, but it can be done elsewhere. I'll close this ticket.