Subject: [bug#54729] [PATCH] build: haskell-build-system: Support packages w. multiple libraries

From: Philip Munksgaard <[email-masked]>
Date: Tue, 5 Apr 2022 17:15:29 +0200

As discussed in #53655 [0], haskell-build-system.scm does not currently
support packages which contain multiple libraries, such as attoparsec
[1]. Such libraries are often used for internal or convenience libraries, as
detailed in the documentation [2].

The current state of affairs means that attoparsec and any other libraries
with similar structure cannot be built on guix, nor can any library or
executable that depends on such a library.

Instead of assuming that `runhaskell Setup.hs --gen-pkg-config=...` always
outputs a single file, we detect whether the result was a directory. If so, we
need to handle each file independently in lexicographic order by calling the
new private function `install-from-config-file`.

Because `install-transitive-deps` can now be called multiple times for each
call to `register`, it has also been amended to support the files already
installed.

0: https://issues.guix.gnu.org/53655
1: https://hackage.haskell.org/package/attoparsec-0.14.4/attoparsec.cabal
2: https://downloads.haskell.org/cabal/Cabal-3.0.0.0/doc/users-guide/installing-packages.html#cmdoption-setup-register-gen-pkg-config
---
 guix/build/haskell-build-system.scm | 34 ++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/guix/build/haskell-build-system.scm b/guix/build/haskell-build-system.scm
index ef6cb316ee..e827e23aba 100644
--- a/guix/build/haskell-build-system.scm
+++ b/guix/build/haskell-build-system.scm
@@ -217,11 +217,13 @@ (define* (register #:key name system inputs outputs #:allow-other-keys)
          (if (not (vhash-assoc id seen))
              (let ((dep-conf  (string-append src  "/" id ".conf"))
                    (dep-conf* (string-append dest "/" id ".conf")))
-               (when (not (file-exists? dep-conf))
+               (unless (file-exists? dep-conf*)
+                 (when (not (file-exists? dep-conf))
                    (error (format #f "File ~a does not exist. This usually means the dependency ~a is missing. Was checking conf-file ~a." dep-conf id conf-file)))
-               (copy-file dep-conf dep-conf*) ;XXX: maybe symlink instead?
-               (loop (vhash-cons id #t seen)
-                     (append lst (conf-depends dep-conf))))
+                 (copy-file dep-conf dep-conf*) ;XXX: maybe symlink instead?
+
+                 (loop (vhash-cons id #t seen)
+                       (append lst (conf-depends dep-conf*)))))
              (loop seen tail))))))
 
   (let* ((out (assoc-ref outputs "out"))
@@ -234,13 +236,12 @@ (define* (register #:key name system inputs outputs #:allow-other-keys)
                                     "/ghc-" version
                                     "/" name ".conf.d"))
          (id-rx (make-regexp "^id:[ \n\t]+([^ \t\n]+)$" regexp/newline))
-         (config-file (string-append out "/" name ".conf"))
+         (config-output (string-append out "/" name ".conf"))
          (params
-          (list (string-append "--gen-pkg-config=" config-file))))
+          (list (string-append "--gen-pkg-config=" config-output))))
     (run-setuphs "register" params)
-    ;; The conf file is created only when there is a library to register.
-    (when (file-exists? config-file)
-      (mkdir-p config-dir)
+
+    (define (install-from-config-file config-file)
       (let* ((contents (call-with-input-file config-file read-string))
              (config-file-name+id (match:substring (first (list-matches id-rx contents)) 1)))
 
@@ -270,10 +271,17 @@ (define* (register #:key name system inputs outputs #:allow-other-keys)
         (install-transitive-deps config-file %tmp-db-dir config-dir)
         (rename-file config-file
                      (string-append config-dir "/"
-                                    config-file-name+id ".conf"))
-        (invoke "ghc-pkg"
-                (string-append "--package-db=" config-dir)
-                "recache")))
+                                    config-file-name+id ".conf"))))
+
+    ;; The conf file is created only when there is a library to register.
+    (when (file-exists? config-output)
+      (mkdir-p config-dir)
+      (if (file-is-directory? config-output)
+          (for-each install-from-config-file (find-files config-output))
+          (install-from-config-file config-output))
+      (invoke "ghc-pkg"
+              (string-append "--package-db=" config-dir)
+              "recache"))
     #t))
 
 (define* (check #:key tests? test-target #:allow-other-keys)
-- 
2.35.1