Extending the dependency syntax
simonmar at microsoft.com
Tue Aug 9 05:35:35 EDT 2005
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.
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],
gnome? ( libglade >= 2,
gtksourceview >= 0.6,
gconf >= 2, [gnome] ),
mozilla? ( mozilla >= 1.4, [mozilla] ),
doc? ( haddock >= 0.6 )
extra-ghc-options: -O0 -DDEBUG
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
'dep1|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.
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