autodetecting dependencies

[A.J. Kehoe IV (Nanoman)]

Stephen Montgomery-Smith wrote:
>So suppose we are building port A.  It turns out that the configure in
>port A autodetects whether package B is present or not.  It will build
>either way.  But if built with package B, it will not operate without it.
>
>So suppose I build port A on machine X which has package B installed.
>Then I create a package from A, and copy the package to machine Y.
>Machine Y does not have package B installed, and so when package A is
>installed, it doesn't work on machine Y.
>
>What are the accepted ways of handling this?
>
>1.  Don't worry about it.  tinderbox builds will never build port A in
>the presence of package B.
>
>2.  Have the Makefile of port A detect whether package B is installed,
>and if it is then add B as a dependency of A.
>
>3.  Cripple the configure in port A so that it doesn't autodetect for
>package B.  (Sometimes this can be done using a suitable CONFIGURE_ARGS,
>but not in my particular situation.)
>
>I prefer the answer (1).  But I am interested in other people's
>opinions.  One problem with (2) or (3) is that the creator of the port
>might never find out which packages could be autodetected by port A's
>configure without performing an exhaustive search of the source code of A.
>
>Thanks, Stephen

In my opinion, it's best to use the OPTIONS framework and to avoid automatic detection entirely.  Consider this problem:

http://docs.freebsd.org/cgi/mid.cgi?20120304190922.GA58789

For your example, I would add this line to port A's Makefile:

OPTIONS=	PORT_B		"Enable Port B" off

I would then replace the automatic detection part of port A's Makefile with something like this:

.if defined(WITH_PORT_B) && !defined(WITHOUT_PORT_B)
RUN_DEPENDS+=	portb-1.0:${PORTSDIR}/category/portb
.endif

So, if you don't want port A built with package B as a dependency, you'd use the default on port A's OPTIONS "dialog" screen, otherwise, you'd put a check beside "PORT_B".

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