Figuring out which packages a PKGBUILD can produce is not trivial, especially since arch became split-overridable and debug packages possible. However, it is essential to have for proper automatic repository management (read: dbscripts).

In comparison, the reverse (figuring out the PKGBUILD from the package) is easy, most of the time: It's either pkgbase or pkgname in .PKGINFO. Well, except for debug packages, which can contain no pkgbase even though they're a split product.

I would like to request an option for makepkg to output the build product filenames; perhaps in a format such as this:

foo-bar-1.0-1-x86_64
foo-baz-1.0-1-x86_64
foo-qux-1.0-1-any

I.e. without PKGEXT. This is combination with the makepkg configs from devtools should allow discovering the packages for each architecture.