Add pre_get_blogs_of_user filter.

[nerrad]

See original discussion on #31746

The filter has been broken out into its own ticket so that discussion on longer term improvement of get_blogs_of_user() can be continued there.

See https://core.trac.wordpress.org/attachment/ticket/31746/31746.3.diff for patch.

[jtsternberg]

Related patch. https://core.trac.wordpress.org/attachment/ticket/31746/31746.3.diff

[jeremyfelt]

36707.diff​ is a riff on/refresh of @jtsternberg's original patch and uses count() rather than empty() to check the returned data from the filter.

Should we start with false instead and allow for the return of an empty array?

[jtsternberg]

Replying to jeremyfelt:

36707.diff​ is a riff on/refresh of @jtsternberg's original patch and uses count() rather than empty() to check the returned data from the filter.

Should we start with false instead and allow for the return of an empty array?

Actually yah, that seems like a good idea, though it probably should be null in keeping with the precedent of other 'pre_* filters in WordPress.

Also, it looks like the static variable is a no-go?

[jeremyfelt]

Replying to jtsternberg:

Should we start with false instead and allow for the return of an empty array?

Actually yah, that seems like a good idea, though it probably should be null in keeping with the precedent of other 'pre_* filters in WordPress.

+1

Also, it looks like the static variable is a no-go?

For this ticket, yes. We can continue discussing improvements to get_blogs_of_user() on #31746.

[jeremyfelt]

In 37326:

Multisite: Add the pre_get_blogs_of_user filter

This allows a plugin to short circuit get_blogs_of_user() in cases where the default behavior of the function is unnecessary or slow. (e.g. A user is a member of thousands of sites.)

Props jsternberg.
See #31746, Fixes #36707.

[jtsternberg]

Thanks @jeremyfelt!