#3268: implement the Cabal ${pkgroot} spec extension
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Reporter: duncan | Owner:
Type: feature request | Status: new
Priority: normal | Milestone: 7.2.1
Component: Package system | Version: 6.10.2
Keywords: | Testcase:
Blockedby: | Difficulty: Unknown
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Comment(by duncan):
Replying to [comment:2 duncan]:
> > * for `ghc-pkg dump`, we prefix each batch of packages with the
`pkgroot` value
> > (choosing some suitable syntax)
>
> Yes. Some suitable syntax we've not yet chosen :-)
I've decided that the simplest thing to do is to just have it as an extra
field:
{{{
pkgroot: /the/path/that/is/the/pkgroot
}}}
So this field may be in the output, but never in the input (if it is it's
ignored like all other unknown fields).
There are two cases:
* `--expand-vars`: in this case `ghc-pkg dump`/`describe` will expand the
`${pkgroot}` and `${pkgrooturl}` vars and will not generate the `pkgroot`
field.
* `--no-expand-vars`: in this case `ghc-pkg dump`/`describe` will not
expand the `${pkgroot}` var, so it will appear literally in the output and
the `pkgroot` field will be generated so that tools know what value to use
for the `${pkgroot}`.
The defaults are:
* `ghc-pkg dump` uses `--no-expand-vars` by default, but this can be
reversed with `--expand-vars`
* `ghc-pkg describe` uses `--expand-vars` by default, but this can be
reversed with `--no-expand-vars`
(Alternatively could be more explicit and say `-(no-)expand-pkgroot`.)
Sound sane?
None of this applies to hugs/nhc style file databases because there tools
always know exactly what the pkgroot is, as it's just the dir containing
the file they read. Because `ghc-pkg` has a looser connection between the
package info and the locations they come from then we need this (or a
similar) extra mechanism.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3268#comment:7>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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