Re: 9.6 TAP tests and extensions

Craig Ringer <craig@2ndquadrant.com> writes:
> While updating an extension for 9.6 I noticed that while the
> $(prove_check) definition is exposed for use by PGXS in
> Makefile.global, extensions can't actually use the TAP tests because
> we don't install the required Perl modules like PostgresNode.pm.

> I don't see any reason not to make this available to extension authors
> and doing so is harmless, so here's a small patch to install it. I
> think it's reasonable to add this to 9.6 even at this late stage; IMO
> it should've been installed from the beginning.

Without taking a position on the merits of this patch per se, I'd like
to say that I find the argument for back-patching into 9.6 and not
further than that to be pretty dubious.  $(prove_check) has been there
since 9.4, and in the past we've often regretted it when we failed
to back-patch TAP infrastructure fixes all the way back to 9.4.

Or to be concrete: how is an extension author, or more to the point an
extension Makefile, supposed to know whether it can use $(prove_check)?
How would this patch change that, and how would extension authors cope
with building against both patched and unpatched trees?  
        regards, tom lane