Previously, the test framework generated a variable name for each
external prereq as a poor man's associative array.  Unfortunately,
prereqs names may not be legal variable names, leading to
unintelligible bash errors like
  test_missing_external_prereq_emacsclient.emacs24_=t: command not found

Using proper associative arrays to track prereqs, in addition to being
much cleaner than generating variable names and using grep to
carefully construct unique string lists, removes restrictions on
prereq names.
---
 test/test-lib.sh |   24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/test/test-lib.sh b/test/test-lib.sh
index 77063a4..f169785 100644
--- a/test/test-lib.sh
+++ b/test/test-lib.sh
@@ -625,18 +625,22 @@ test_have_prereq () {
 	esac
 }
 
+declare -A test_missing_external_prereq_
+declare -A test_subtest_missing_external_prereq_
+
 # declare prerequisite for the given external binary
 test_declare_external_prereq () {
 	binary="$1"
 	test "$#" = 2 && name=$2 || name="$binary(1)"
 
-	hash $binary 2>/dev/null || eval "
-	test_missing_external_prereq_${binary}_=t
+	if ! hash $binary 2>/dev/null; then
+		test_missing_external_prereq_["${binary}"]=t
+		eval "
 $binary () {
-	echo -n \"\$test_subtest_missing_external_prereqs_ \" | grep -qe \" $name \" ||
-	test_subtest_missing_external_prereqs_=\"\$test_subtest_missing_external_prereqs_ $name\"
+	test_subtest_missing_external_prereq_[\"${name}\"]=t
 	false
 }"
+	fi
 }
 
 # Explicitly require external prerequisite.  Useful when binary is
@@ -644,7 +648,7 @@ $binary () {
 # Returns success if dependency is available, failure otherwise.
 test_require_external_prereq () {
 	binary="$1"
-	if [ "$(eval echo -n \$test_missing_external_prereq_${binary}_)" = t ]; then
+	if [[ ${test_missing_external_prereq_["${binary}"]} == t ]]; then
 		# dependency is missing, call the replacement function to note it
 		eval "$binary"
 	else
@@ -737,9 +741,9 @@ test_skip () {
 }
 
 test_check_missing_external_prereqs_ () {
-	if test -n "$test_subtest_missing_external_prereqs_"; then
-		say_color skip >&1 "missing prerequisites:"
-		echo "$test_subtest_missing_external_prereqs_" >&1
+	if [[ ${#test_subtest_missing_external_prereq_[@]} != 0 ]]; then
+		say_color skip >&1 "missing prerequisites: "
+		echo ${!test_subtest_missing_external_prereq_[@]} >&1
 		test_report_skip_ "$@"
 	else
 		false
@@ -1022,7 +1026,7 @@ test_python() {
 	# most others as /usr/bin/python. So first try python2, and fallback to
 	# python if python2 doesn't exist.
 	cmd=python2
-	[[ "$test_missing_external_prereq_python2_" = t ]] && cmd=python
+	[[ ${test_missing_external_prereq_[python2]} == t ]] && cmd=python
 
 	(echo "import sys; _orig_stdout=sys.stdout; sys.stdout=open('OUTPUT', 'w')"; cat) \
 		| $cmd -
@@ -1064,7 +1068,7 @@ test_reset_state_ () {
 	test -z "$test_init_done_" && test_init_
 
 	test_subtest_known_broken_=
-	test_subtest_missing_external_prereqs_=
+	test_subtest_missing_external_prereq_=()
 }
 
 # called once before the first subtest
-- 
1.7.10.4