test: fix check for updatectl

The have_updatectl variable is meant to gracefully handle the case where
updatectl is missing. But, because the script runs with -e, it fails
immediately in that case instead. Moreover, expanding $have_updatectl
when it is present actually executes updatectl, rather than simply
checking for its existence.

Re-factor this check so that it does handle a missing updatectl.

test/units/TEST-72-SYSUPDATE.sh

@@ -7,6 +7,7 @@ set -o pipefail
 
 SYSUPDATE=/usr/bin/systemd-sysupdate
 SYSUPDATED=/lib/systemd/systemd-sysupdated
+UPDATECTL=""
 SECTOR_SIZES=(512 4096)
 WORKDIR="$(mktemp -d /var/tmp/test-72-XXXXXX)"
 CONFIGDIR="/run/sysupdate.d"
@@ -21,7 +22,9 @@ if [[ ! -x "$SYSUPDATE" ]]; then
     exit 77
 fi
 
-have_updatectl=$([[ -x "$SYSUPDATED" ]] && command -v updatectl)
+if [[ -x "$SYSUPDATED" ]]; then
+    UPDATECTL="$(command -v updatectl || true)"
+fi
 
 # Loopback devices may not be supported. They are used because sfdisk cannot
 # change the sector size of a file, and we want to test both 512 and 4096 byte
@@ -140,9 +143,9 @@ update_now() {
         "$SYSUPDATE" --verify=no acquire
         "$SYSUPDATE" --verify=no update
     elif [[ "$update_type" == "updatectl" ]]; then
-        if $have_updatectl; then
+        if [[ -x "$UPDATECTL" ]]; then
             systemctl start systemd-sysupdated
-            updatectl update
+            "$UPDATECTL" update
         else
             # Gracefully fall back to sysupdate
             "$SYSUPDATE" --verify=no update
@@ -432,10 +435,10 @@ EOF
     # Create sixth version, update using updatectl and verify it replaced the
     # correct version
     new_version "$sector_size" v6
-    if $have_updatectl; then
+    if [[ -x "$UPDATECTL" ]]; then
         systemctl start systemd-sysupdated
         "$SYSUPDATE" --verify=no check-new
-        updatectl update |& tee "$WORKDIR"/updatectl-update-6
+        "$UPDATECTL" update |& tee "$WORKDIR"/updatectl-update-6
         grep "Done" "$WORKDIR"/updatectl-update-6
         (! grep "Already up-to-date" "$WORKDIR"/updatectl-update-6)
     else
@@ -452,13 +455,13 @@ EOF
     # testing for specific output, but this will at least catch obvious crashes
     # and allow updatectl to run under the various sanitizers. We create a
     # component so that updatectl has multiple targets to list.
-    if $have_updatectl; then
+    if [[ -x "$UPDATECTL" ]]; then
         mkdir -p /run/sysupdate.test.d/
         cp "$CONFIGDIR/01-first.transfer" /run/sysupdate.test.d/01-first.transfer
-        verify_object_fields "$(updatectl list 2>&1)"
-        verify_object_fields "$(updatectl list host 2>&1)"
-        verify_object_fields "$(updatectl list host@v6 2>&1)"
-        updatectl check
+        verify_object_fields "$("$UPDATECTL" list 2>&1)"
+        verify_object_fields "$("$UPDATECTL" list host 2>&1)"
+        verify_object_fields "$("$UPDATECTL" list host@v6 2>&1)"
+        "$UPDATECTL" check
         rm -r /run/sysupdate.test.d
     fi