[bug#49199] [PATCH core-updates] add package-db to runhaskell (haskell-build-system)

[John Kehayias via Guix-patches via <guix-patches@gnu.org>]

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Hello,

This is a patch to fix issue #48944 as well as more broadly an issue of Haskell packages that need modules at the configure step. Currently the package database is not passed to runhaskell directly, which means runhaskell Setup.hs configure does not have outside modules available. This blocks packages that need things like cabal-doctest or gtk2hs-buildtools like ghc-cairo (which has a custom build process in the package currently, for this reason). Comments in ghc-cairo and for other packages with this need, suggest the change made in this patch.

The simplest change I saw was to make the package database passed to runhaskell on any command; not sure if this would be better for just configure. It may be possible to do this just passing the actual needed packages with -package-id, as suggested in https://github.com/tweag/rules_haskell/issues/1314 However, I have not tried that and seemed more complicated than needed. Also, I did not modify the message printed as it already has the package-db in params, but perhaps better to be clear the exact command being run?

I have built many Haskell packages with this change and it works well for me, fixing the reported issue and packages I'm building not yet in guix. Given this changes the build command for all Haskell packages, would be happy for other tests to be run.

John

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diff --git a/guix/build/haskell-build-system.scm b/guix/build/haskell-build-system.scm
index 28253ce2f0..be20f13e10 100644
--- a/guix/build/haskell-build-system.scm
+++ b/guix/build/haskell-build-system.scm
@@ -63,13 +63,14 @@
                      ((file-exists? "Setup.lhs")
                       "Setup.lhs")
                      (else
-                      #f))))
+                      #f)))
+        (pkgdb (string-append "-package-db=" %tmp-db-dir)))
     (if setup-file
         (begin
           (format #t "running \"runhaskell Setup.hs\" with command ~s \
 and parameters ~s~%"
                   command params)
-          (apply invoke "runhaskell" setup-file command params))
+          (apply invoke "runhaskell" pkgdb setup-file command params))
         (error "no Setup.hs nor Setup.lhs found"))))
 
 (define* (configure #:key outputs inputs tests? (configure-flags '())
-- 
2.32.0