Extending the dependency syntax
ijones at syntaxpolice.org
Tue Aug 9 11:47:43 EDT 2005
"Simon Marlow" <simonmar at microsoft.com> writes:
> I'd like to wrap up this little design issue which stalled. I'll
> propose something a little simpler, which should hopefully be closer to
> what people are used to from other package systems, and which should
> translate more easily.
The more I think about your proposal, the more I like it. I've
already thought of a lot of places where I could use it.
> To recap, the goal is to support:
> - build options that result in an executable or library being built
> in a different way, or with a particular feature. The build option
> may imply additional dependencies.
> - a choice between dependencies, where the particular choice made
> dictates certain configuration changes in the build info.
> - a choice between configurations, for example building a library
> with or without debugging support.
> An example first showing all the main ideas:
> ghc? (ghc >= 6.4, [ghc64] | ghc >= 5.04, [ghc-old])
> | hugs? [hugs],
> (HUnit-1.0, [debug])
> gnome? ( libglade >= 2,
> gtksourceview >= 0.6,
> gconf >= 2, [gnome] ),
> mozilla? ( mozilla >= 1.4, [mozilla] ),
> doc? ( haddock >= 0.6 )
> extra-libraries: gnome
> extra-ghc-options: -DENABLE_GNOME
I would prefer something like:
to keep the stanza syntax consistent.
> extra-ghc-options: -O0 -DDEBUG
> extra-ghc-options: -O2
Do you have any ideas for how to interact with environment variables?
I wasn't clear if your previous proposal included this or not... for
instance, you might want to say:
DEBUG=true ./setup build
(can you do that on Windows?)
> The semantics of build-depends:
> - ',' means "and", just as it does now
> - '|' means "or"
> - parentheses group dependencies
> - [name] means "read the optional stanza [name]"
> - 'flag? dep' means "if the --enable-flag option is given, then
> dep, otherwise nothing".
> - 'flag? dep1 dep2' menas "if the --enable-flag option is given
> then dep1, else dep2".
> Additionally, we could have an --auto-enable flag, which has the effect
> of replacing every 'flag? dep' by 'dep|', and 'flag? dep1 dep2' by
By 'dep|' you mean "this dependency or nothing"? So should the 2nd
example be 'deb1|dep2|'?
> This has the effect of turning on every option for which
> the dependencies are satisfied, which is normally what you want when
> building a package for local use.
> I'm not attached to any particular syntax, so feel free to suggest
> This is somewhat simpler than before, and I think supports everything we
> need. Comments? I'm happy to implement if there's a concensus.
I'm pretty happy. I think someone should put together a couple of
examples from questions we've had on here first, though :)
Do you actually like this better, or are you toning it down because of
my previous stressing over the complexity?
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