From a090d0a7c9168ca6292c6cdf1b8c27c5a067c085 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Thu, 7 Jul 2022 21:56:17 -0400
Subject: Automatically add Haunt's modules to Guile's load path at startup.
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This fixes a longstanding usability issue where people would install
Haunt to /usr/local and then wonder why Haunt doesn't work, which was
because Guile's default load path is /usr and thus could not find the
newly installed modules in /usr/local.  I received several emails
about this over the years and didn't know to deal with it.  Many
thanks to Daniel Meißner for pointing out that Guix had already found
a solution to this problem because of course Guix would have this
problem solved!  Ludovic is an autotools wizard.
---
 .gitignore       |  1 +
 configure.ac     | 10 ++++++++++
 pre-inst-env.in  |  2 ++
 scripts/haunt.in |  9 +++++++++
 4 files changed, 22 insertions(+)

diff --git a/.gitignore b/.gitignore
index b6c42ce..a472436 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@ Makefile
 Makefile.in
 /aclocal.m4
 /autom4te.cache/
+/build-aux/
 /config.log
 /config.status
 /configure
diff --git a/configure.ac b/configure.ac
index da381d3..67e287c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -14,6 +14,16 @@ AC_CONFIG_FILES([scripts/haunt], [chmod +x scripts/haunt])
 GUILE_PKG([3.0 2.2 2.0])
 GUILE_PROGS
 
+dnl Compute complete installation directories for .scm and .go files
+dnl so that the Haunt executable can automagically add them to Guile's
+dnl load path.
+haunt_prefix="`eval echo $prefix | sed -e"s|NONE|/usr/local|g"`"
+haunt_libdir="`eval echo $libdir | sed -e"s|NONE|$haunt_prefix|g"`"
+guilemoduledir="`eval echo ${datarootdir}/guile/site/$GUILE_EFFECTIVE_VERSION | sed -e"s|NONE|$haunt_prefix|g"`"
+guileobjectdir="`eval echo ${libdir}/guile/$GUILE_EFFECTIVE_VERSION/site-ccache | sed -e"s|NONE|$haunt_prefix|g"`"
+AC_SUBST([guilemoduledir])
+AC_SUBST([guileobjectdir])
+
 dnl Guile-reader is needed for Skribe support
 GUILE_MODULE_AVAILABLE([have_guile_reader], [(system reader)])
 AM_CONDITIONAL([HAVE_GUILE_READER], [test "x$have_guile_reader" = "xyes"])
diff --git a/pre-inst-env.in b/pre-inst-env.in
index 84c88ca..8a3ad0a 100644
--- a/pre-inst-env.in
+++ b/pre-inst-env.in
@@ -28,4 +28,6 @@ export GUILE_LOAD_COMPILED_PATH GUILE_LOAD_PATH
 PATH="$abs_top_builddir/scripts:$PATH"
 export PATH
 
+HAUNT_UNINSTALLED=true
+
 exec "$@"
diff --git a/scripts/haunt.in b/scripts/haunt.in
index 7206036..dd25efb 100755
--- a/scripts/haunt.in
+++ b/scripts/haunt.in
@@ -19,6 +19,15 @@
 ;;; You should have received a copy of the GNU General Public License
 ;;; along with Haunt.  If not, see <http://www.gnu.org/licenses/>.
 
+(define-syntax-rule (push! elt v) (set! v (cons elt v)))
+
+;; Automatically add Haunt modules to Guile's load path so that users
+;; aren't wondering why Haunt isn't working when the modules aren't
+;; installed to Guile's default module locations.
+(unless (getenv "HAUNT_UNINSTALLED")
+  (push! "@guilemoduledir@" %load-path)
+  (push! "@guileobjectdir@" %load-compiled-path))
+
 (use-modules (haunt ui))
 
 (apply haunt-main (command-line))
-- 
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