From 723bdb8ef0175716a2bfa93e96c3fd757d7b2679 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <ludo@gnu.org>
Date: Sat, 20 Jul 2019 00:33:50 +0200
Subject: [PATCH] ui: 'warn-about-load-error' provides hints for unbound
 variables.

* guix/ui.scm (warn-about-load-error): Add 'unbound-variable' clause.
* tests/guix-build.sh: Add test.
---
 guix/ui.scm         |  2 ++
 tests/guix-build.sh | 19 +++++++++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/guix/ui.scm b/guix/ui.scm
index 1812b01272..7920335928 100644
--- a/guix/ui.scm
+++ b/guix/ui.scm
@@ -392,6 +392,8 @@ exiting.  ARGS is the list of arguments received by the 'throw' handler."
     (('syntax-error proc message properties form . rest)
      (let ((loc (source-properties->location properties)))
        (warning loc (G_ "~a~%") message)))
+    (('unbound-variable _ ...)
+     (report-unbound-variable-error args))
     (('srfi-34 obj)
      (if (message-condition? obj)
          (warning (G_ "failed to load '~a': ~a~%")
diff --git a/tests/guix-build.sh b/tests/guix-build.sh
index d16b92d189..37666ffd01 100644
--- a/tests/guix-build.sh
+++ b/tests/guix-build.sh
@@ -146,8 +146,8 @@ test `guix build -d --sources=transitive foo \
       | wc -l` -eq 3
 
 
-# Unbound variables.
-cat > "$module_dir/foo.scm"<<EOF
+# Unbound variable in thunked field.
+cat > "$module_dir/foo.scm" <<EOF
 (define-module (foo)
   #:use-module (guix tests)
   #:use-module (guix build-system trivial))
@@ -162,6 +162,21 @@ if guix build package-with-something-wrong -n; then false; else true; fi
 guix build package-with-something-wrong -n 2> "$module_dir/err" || true
 grep "unbound" "$module_dir/err"		     # actual error
 grep "forget.*(gnu packages base)" "$module_dir/err" # hint
+
+# Unbound variable at the top level.
+cat > "$module_dir/foo.scm" <<EOF
+(define-module (foo)
+  #:use-module (guix tests))
+
+(define-public foo
+  (dummy-package "package-with-something-wrong"
+    (build-system gnu-build-system)))      ;unbound variable
+EOF
+
+guix build sed -n 2> "$module_dir/err"
+grep "unbound" "$module_dir/err"		     # actual error
+grep "forget.*(guix build-system gnu)" "$module_dir/err" # hint
+
 rm -f "$module_dir"/*
 
 # Wrong 'define-module' clause reported by 'warn-about-load-error'.