setup-user: avoid eternal loop on adduser failure

Make sure we dont loop forever if adduser fails to create the user.

fixes https://gitlab.alpinelinux.org/alpine/alpine-conf/-/issues/10519

setup-user.in

@@ -55,6 +55,10 @@ while true; do
 		else
 			suggest=no
 		fi
+		# dont suggest something that has failed before
+		if [ "$suggest" = "$failed_username" ]; then
+			suggest=
+		fi
 		ask "Setup a user? (enter a lower-case loginname, or 'no')" $suggest
 		case "$resp" in
 			no) exit 0;;
@@ -76,6 +80,8 @@ while true; do
 	if ! [ -n "$interactive" ]; then
 		exit 1
 	fi
+	failed_username="$username"
+	username=
 done
 
 if [ -n "$interactive" ] && [ -z "$keysopt" ]; then

tests/setup_user_test

@@ -7,6 +7,7 @@ init_tests \
 	setup_user_interactive_no \
 	setup_user_interactive \
 	setup_user_interactive_fullname \
+	setup_user_interactive_fullname_existing \
 	setup_user_interactive_singlename \
 	setup_user_interactive_suggest_ssh \
 	setup_user_groups_commas \
@@ -74,6 +75,20 @@ setup_user_interactive_fullname_body() {
 		setup-user -f "Joe User" -k none <answers
 }
 
+setup_user_interactive_fullname_existing_body() {
+	init_env
+	(
+		echo "existinguser"
+		echo "testuser"
+	) >answers
+	ADDUSER_EXIST=existinguser atf_check -s exit:0 \
+		-o match:"Setup a user.*\[existinguser\]" \
+		-o match:"Setup a user.*\) adduser" \
+		-o match:"adduser.* -g existinguser .*testuser" \
+		-e match:"adduser: user 'existinguser' in use" \
+		setup-user -f "existinguser" -k none <answers
+}
+
 setup_user_interactive_singlename_body() {
 	init_env
 	echo "" >answers