[pacman-dev] [PATCH] Added mirror support to makepkg's source array.

[Xyne]

On 2013-11-15 21:06 +1000
Allan McRae wrote:

>An idea is doing:
>
>source=("mirror://file.tar.gz")
>mirror=("http://foo.com/" "http://bar.com/")
>
>makepkg would replace "mirror://" in the source line with a value from
>the "mirror" array and try downloading from each one until success or
>total failure.
>
>To allow multiple sources to have different mirrors, I am proposing we
>detect an unknown protocol in the url and look for the corresponding
>array.  e.g. we could have source=("sourceforge://file.tar.gz") and look
>for the "sourceforge" array.
>
>Comments or other ideas?

Detecting "unknown" protocols is not future proof and will lead to an easy but
never-ending game of whack-a-mole. It would also lead to unnecessary repetition
in the "mirror" array.

I think it would be better to use a variable delimiter (possibly an illegal URL
character, or a PKGBUILD-variable for maximum flexibility), e.g.

source_delim='*'
source=("http://*mirror*file.tar.gz")
mirror=("foo.com/" "bar.com/")

You could even use "source_" as a prefix for the source variables to avoid
namespace polution (source_mirror, source_foo, etc).

Allowing variables at arbitrary points provides greater flexibility and
reduces verbosity (e.g. the repetition of the scheme in this case). If you
really want to limit this to URL prefixes, then I suggest enforcing a policy of
using lower-case schemes for regular URLs and upper-case pseudo-schemes for
mirrors, e.g.

source=("MIRROR://file.tar.gz")
MIRROR=("http://foo.com/" "http://bar.com/")

While I think the previous approach is better, this would also avoid the
eventual grief of a hard-coded list of recognized protocols.


Incidentally, if you generalize this enough you could probably re-use the code
to implement dependency alternatives, if you are interested in that. The logic
overlaps.

Regards,
Xyne