build: 'make check' errors out if file name limits would be hit.

* Makefile.am (SCM_TESTS, SH_TESTS, TESTS, AM_TESTS_ENVIRONMENT)
(SCM_LOG_COMPILER, SH_LOG_COMPILER, AM_SCM_LOG_FLAGS)
(AM_SH_LOG_FLAGS): Move within 'if CAN_RUN_TESTS'.
(check-local) [!CAN_RUN_TESTS]: New target.
* daemon.am (AM_TESTS_ENVIRONMENT, TESTS): Ditto.
* m4/guix.m4 (GUIX_CHECK_FILE_NAME_LIMITS): Add parameter and set it.

Makefile.am

 # GNU Guix --- Functional package management for GNU
-# Copyright © 2012, 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
+# Copyright © 2012, 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
 # Copyright © 2013 Andreas Enge <andreas@enge.fr>
 # Copyright © 2015 Alex Kost <alezost@gmail.com>
 #
@@ -135,6 +135,18 @@ MODULES =					\
   guix.scm					\
   $(GNU_SYSTEM_MODULES)
 
+if HAVE_GUILE_JSON
+
+MODULES +=					\
+  guix/import/json.scm				\
+  guix/import/pypi.scm				\
+  guix/scripts/import/pypi.scm			\
+  guix/import/cpan.scm				\
+  guix/scripts/import/gem.scm			\
+  guix/import/gem.scm
+
+endif
+
 if BUILD_SYSCALLS_MODULE
 
 MODULES +=					\
@@ -191,6 +203,11 @@ clean-go:
 	-$(RM) -f $(GOBJECTS)
 
 
+# Test extensions; has to be unconditional.
+TEST_EXTENSIONS = .scm .sh
+
+if CAN_RUN_TESTS
+
 SCM_TESTS =					\
   tests/base32.scm				\
   tests/base64.scm				\
@@ -233,14 +250,6 @@ SCM_TESTS =					\
 
 if HAVE_GUILE_JSON
 
-MODULES +=					\
-  guix/import/json.scm				\
-  guix/import/pypi.scm				\
-  guix/scripts/import/pypi.scm			\
-  guix/import/cpan.scm				\
-  guix/scripts/import/gem.scm			\
-  guix/import/gem.scm
-
 SCM_TESTS += 					\
   tests/pypi.scm				\
   tests/cpan.scm				\
@@ -272,8 +281,6 @@ endif BUILD_DAEMON
 
 TESTS = $(SCM_TESTS) $(SH_TESTS)
 
-TEST_EXTENSIONS = .scm .sh
-
 AM_TESTS_ENVIRONMENT = abs_top_srcdir="$(abs_top_srcdir)"
 
 SCM_LOG_COMPILER = $(top_builddir)/test-env $(GUILE)
@@ -289,6 +296,22 @@ tests/guix-gc.log:							\
   $(patsubst %.sh,%.log,$(filter-out tests/guix-gc.sh,$(SH_TESTS)))	\
   $(SCM_TESTS:%.scm=%.log)
 
+else !CAN_RUN_TESTS
+
+TESTS =
+SH_TESTS =
+SCM_TESTS =
+
+# Automake always generates a 'check' target, so better not override it.
+check-local:
+	@echo
+	@echo "Cannot run tests because file name limits would be exceeded." >&2
+	@echo "Look for 'length' in the 'config.log' file for details." >&2
+	@echo
+	@exit 1
+
+endif !CAN_RUN_TESTS
+
 # Public key used to sign substitutes from hydra.gnu.org.
 dist_pkgdata_DATA = hydra.gnu.org.pub
 

configure.ac

@@ -60,7 +60,8 @@ AC_SUBST([guix_localstatedir])
 AC_SUBST([guix_sysconfdir])
 AC_SUBST([guix_sbindir])
 
-GUIX_CHECK_FILE_NAME_LIMITS
+GUIX_CHECK_FILE_NAME_LIMITS([can_run_tests])
+AM_CONDITIONAL([CAN_RUN_TESTS], [test "x$can_run_tests" = "xyes"])
 
 dnl We require pkg.m4 (from pkg-config) and guile.m4 (from Guile.)
 dnl Make sure they are available.

daemon.am

 # GNU Guix --- Functional package management for GNU
-# Copyright © 2012, 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
+# Copyright © 2012, 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
 #
 # This file is part of GNU Guix.
 #
@@ -208,12 +208,16 @@ EXTRA_DIST +=					\
   etc/guix-daemon.service.in	\
   etc/guix-daemon.conf.in
 
+if CAN_RUN_TESTS
+
 AM_TESTS_ENVIRONMENT +=				\
   top_builddir="$(abs_top_builddir)"
 
 TESTS +=					\
   tests/guix-daemon.sh
 
+endif CAN_RUN_TESTS
+
 clean-local:
 	-if test -d "$(GUIX_TEST_ROOT)"; then		\
 	  find "$(GUIX_TEST_ROOT)" | xargs chmod +w;	\

m4/guix.m4

@@ -215,7 +215,8 @@ AC_DEFUN([GUIX_TEST_HASH_BANG_LENGTH], [
 dnl GUIX_CHECK_FILE_NAME_LIMITS
 dnl
 dnl GNU/Linux has a couple of silly limits that we can easily run into.
-dnl Make sure everything is fine with the current settings.
+dnl Make sure everything is fine with the current settings.  Set $1 to
+dnl 'yes' if tests can run, 'no' otherwise.
 AC_DEFUN([GUIX_CHECK_FILE_NAME_LIMITS], [
   AC_REQUIRE([GUIX_SOCKET_FILE_NAME_LENGTH])
   AC_REQUIRE([GUIX_TEST_SOCKET_FILE_NAME_LENGTH])
@@ -228,10 +229,14 @@ AC_DEFUN([GUIX_CHECK_FILE_NAME_LIMITS], [
   if test "$ac_cv_guix_test_socket_file_name_length" -ge ]SOCKET_FILE_NAME_LIMIT[; then
     AC_MSG_WARN([socket file name limit may be exceeded when running tests])
   fi
+
+  $1=yes
   if test "$ac_cv_guix_hash_bang_length" -ge ]LINUX_HASH_BANG_LIMIT[; then
+    $1=no
     AC_MSG_ERROR([store directory '$storedir' would lead to overly long hash-bang lines])
   fi
   if test "$ac_cv_guix_test_hash_bang_length" -ge ]LINUX_HASH_BANG_LIMIT[; then
+    $1=no
     AC_MSG_WARN([test directory '$ac_cv_guix_test_root' may lead to overly long hash-bang lines])
   fi
 ])