fleetd #528: pin drain_gate_refusal's call site, not just the predicate

drain_gate_refusal composes the correct abort message and is well tested,
but the main flow built its own `die "$(drain_gate_refusal ...)"` call —
nothing proved that call site was ever consulted. Mutating it to a flat
`die "aborted -- nothing changed"` left the whole suite green, silently
reinstating the exact defect #517 was filed to fix.

Same shape as #521/#526's should_swap/swap_if_built: the decision and the
die() now live together in refuse_drain_gate, which the main flow calls
unconditionally. drain_gate_refusal stays separate and separately tested
for the message logic; four new behavioural tests stub die() to prove
refuse_drain_gate calls it correctly for all four cases, and a fifth
source-text test pins the main flow's call site itself (the only thing
that can catch deleting the call, since sourcing stops before the main
flow runs).

scripts/redeploy-fleetd.sh

@@ -519,6 +519,32 @@ drain_gate_refusal() {
   fi
 }
 
+# fleetd #528 — drain_gate_refusal above is well tested (four cases, all direct), but nothing made
+# the MAIN FLOW's abort actually consult it. Before this, the main flow read
+# `die "$(drain_gate_refusal "$DO_BUILD" "$JAR_STAGED")"` directly, and mutating that one line to a
+# flat `die "aborted — nothing changed"` left the whole suite at exit 0 with zero FAIL lines and
+# byte-identical output to a clean run — every one of drain_gate_refusal's own tests still passed,
+# because they call the predicate directly and never touch this call site. That silently reinstated
+# the exact defect #517 was filed to fix. Same shape as #521/#526's should_swap/swap_if_built: a
+# predicate alone is not enough, because a test proving the predicate is right cannot also prove the
+# main flow consults it. So the decision (drain_gate_refusal) and the action (die) now live together
+# in ONE function, and the main flow calls it unconditionally instead of building the die() call
+# itself — there is no guard left in the main flow to remove, invert, or bypass independently of this
+# function. drain_gate_refusal stays separate and separately tested because the message-selection
+# logic is worth naming and testing on its own; refuse_drain_gate is the only thing that ever dies.
+#
+# What the behavioural tests above still cannot pin on their own: deleting the call to this function
+# from the main flow altogether — they call refuse_drain_gate directly, never through the main flow,
+# because sourcing stops before the main flow ever runs (see the SOURCED guard below). That gap is
+# closed the same way swap_if_built's is: test_refuse_drain_gate_call_site_present greps this script
+# for the real invocation, the same shape test_swap_ordered_after_wait_and_before_start already uses
+# for the swap call. Deliberately NOT written out here as a literal quoted string, so this comment
+# itself can never become a second match for that test's needle.
+refuse_drain_gate() {
+  local do_build="$1" staged_path="$2"
+  die "$(drain_gate_refusal "$do_build" "$staged_path")"
+}
+
 # CB-600: sourceable for testing. When this file is SOURCED (not executed) it stops here — nothing
 # below runs — so a test harness can `source` it to call check_log_path_matches_plist (or the
 # other pure helpers above) against a throwaway plist fixture without ever reaching the mutating
@@ -677,10 +703,11 @@ if [ -n "$OLD_PID" ] && [ "$ASSUME_YES" = 0 ]; then
   echo
   read -r -p "   Fleet drained? type yes to restart: " reply
   if [ "$reply" != "yes" ]; then
-    # fleetd #493 / #517: "nothing changed" would be a lie once a build has run and staged a jar —
-    # see drain_gate_refusal above for the full decision and why each of its four cases reads the
-    # way it does.
-    die "$(drain_gate_refusal "$DO_BUILD" "$JAR_STAGED")"
+    # fleetd #493 / #517 / #528: "nothing changed" would be a lie once a build has run and staged a
+    # jar — see drain_gate_refusal above for the full decision and why each of its four cases reads
+    # the way it does. refuse_drain_gate composes that message AND calls die itself, so this guard
+    # has nothing left of its own to get wrong beyond whether it calls refuse_drain_gate at all.
+    refuse_drain_gate "$DO_BUILD" "$JAR_STAGED"
   fi
 fi
 

scripts/test-redeploy-fleetd.sh

@@ -521,6 +521,106 @@ test_drain_gate_refusal_no_build_staged_absent() {
   assert_equals "aborted — nothing changed" "$result" "no-build+staged-absent refusal wording"
 }
 
+# fleetd #528 — the four tests above pin drain_gate_refusal(), and that is ALL they pin: they call
+# the predicate directly and never touch the main flow's call site. That was measured to be not
+# enough, the same way test_should_swap_true_when_build_ran/test_should_swap_false_when_build_skipped
+# were not enough for #521: with the main flow reading `die "$(drain_gate_refusal "$DO_BUILD"
+# "$JAR_STAGED")"`, replacing that whole line with a flat `die "aborted — nothing changed"` left this
+# suite at exit 0 with zero FAIL lines and byte-identical output to a clean run. Nothing above could
+# tell the difference, because none of it calls anything at or above the call site itself.
+#
+# So these four call refuse_drain_gate() — the function the main flow actually calls, holding the
+# composed message and the die() together — with die() stubbed to RECORD whether it was called and
+# with what message, instead of exiting the process. That fails if refuse_drain_gate stops consulting
+# drain_gate_refusal, mangles what it passes it, or simply never calls die.
+#
+# What none of these four can catch: deleting the `refuse_drain_gate "$DO_BUILD" "$JAR_STAGED"` line
+# from the main flow altogether — see the comment above refuse_drain_gate in redeploy-fleetd.sh for
+# why no test in this file can do better than that (sourcing stops before the main flow runs).
+DIED_CALLED=0
+DIED_MESSAGE=""
+stub_die_recorder() {
+  DIED_CALLED=0
+  DIED_MESSAGE=""
+  die() { DIED_CALLED=1; DIED_MESSAGE="$*"; }
+}
+
+test_refuse_drain_gate_build_ran_staged_present() {
+  source "$ROOT/scripts/redeploy-fleetd.sh"
+  local dir staged
+  dir="$TMP/refuse-drain-build-staged"; mkdir -p "$dir"
+  staged="$dir/fleetd-new.jar"
+  printf 'staged jar bytes' > "$staged"
+  stub_die_recorder
+  refuse_drain_gate 1 "$staged"
+  [ "$DIED_CALLED" = 1 ] \
+    || fail "refuse_drain_gate build-ran+staged-present must call die, and did not"
+  printf '%s' "$DIED_MESSAGE" | grep -qF "$staged" \
+    || fail "refuse_drain_gate build-ran+staged-present die message does not name the staged jar"
+  printf '%s' "$DIED_MESSAGE" | grep -qF 'Rerun WITHOUT --no-build' \
+    || fail "refuse_drain_gate build-ran+staged-present die message is missing the rerun instruction"
+  if printf '%s' "$DIED_MESSAGE" | grep -qF 'nothing changed'; then
+    fail "refuse_drain_gate build-ran+staged-present must not claim nothing changed — the jar already moved"
+  fi
+  source "$ROOT/scripts/redeploy-fleetd.sh"
+}
+
+test_refuse_drain_gate_build_ran_staged_absent() {
+  source "$ROOT/scripts/redeploy-fleetd.sh"
+  local dir
+  dir="$TMP/refuse-drain-build-no-staged"; mkdir -p "$dir"
+  stub_die_recorder
+  refuse_drain_gate 1 "$dir/fleetd-new.jar"
+  [ "$DIED_CALLED" = 1 ] \
+    || fail "refuse_drain_gate build-ran+staged-absent must call die, and did not"
+  assert_equals "aborted — nothing changed" "$DIED_MESSAGE" "refuse_drain_gate build-ran+staged-absent die message"
+  source "$ROOT/scripts/redeploy-fleetd.sh"
+}
+
+test_refuse_drain_gate_no_build_staged_present() {
+  source "$ROOT/scripts/redeploy-fleetd.sh"
+  local dir staged
+  dir="$TMP/refuse-drain-no-build-staged"; mkdir -p "$dir"
+  staged="$dir/fleetd-new.jar"
+  printf 'leftover staged jar bytes' > "$staged"
+  stub_die_recorder
+  refuse_drain_gate 0 "$staged"
+  [ "$DIED_CALLED" = 1 ] \
+    || fail "refuse_drain_gate no-build+staged-present must call die, and did not"
+  assert_equals "aborted — nothing changed" "$DIED_MESSAGE" "refuse_drain_gate no-build+staged-present die message"
+  source "$ROOT/scripts/redeploy-fleetd.sh"
+}
+
+test_refuse_drain_gate_no_build_staged_absent() {
+  source "$ROOT/scripts/redeploy-fleetd.sh"
+  local dir
+  dir="$TMP/refuse-drain-no-build-no-staged"; mkdir -p "$dir"
+  stub_die_recorder
+  refuse_drain_gate 0 "$dir/fleetd-new.jar"
+  [ "$DIED_CALLED" = 1 ] \
+    || fail "refuse_drain_gate no-build+staged-absent must call die, and did not"
+  assert_equals "aborted — nothing changed" "$DIED_MESSAGE" "refuse_drain_gate no-build+staged-absent die message"
+  source "$ROOT/scripts/redeploy-fleetd.sh"
+}
+
+# fleetd #528 — closes the one gap the four behavioural tests above cannot: they call
+# refuse_drain_gate directly, and sourcing stops before the main flow ever runs (the SOURCED guard),
+# so none of them can prove the main flow still CALLS refuse_drain_gate at all. Same shape as
+# test_swap_ordered_after_wait_and_before_start: a source-text grep for the real call site. This is
+# what actually kills the item-1 mutation from the ticket — replacing the main flow's call with a
+# flat `die "aborted — nothing changed"` removes this exact needle, where none of the behavioural
+# tests above would even notice.
+#
+# The grep ends `|| true`: this file runs under `set -euo pipefail`, so an ABSENT needle would fail
+# the assignment and `set -e` would kill the whole suite before the `[ -n ... ] || fail` guard below
+# ever ran — the exact dead-check shape fleetd #528 also flags as a sweep finding (see the PR body).
+test_refuse_drain_gate_call_site_present() {
+  local src="$ROOT/scripts/redeploy-fleetd.sh" call_line
+  call_line="$(grep -Fn 'refuse_drain_gate "$DO_BUILD" "$JAR_STAGED"' "$src" | head -1 | cut -d: -f1 || true)"
+  [ -n "$call_line" ] \
+    || fail "could not find the main flow's refuse_drain_gate call site in redeploy-fleetd.sh"
+}
+
 test_no_errors() {
   cat > "$TMP/no-errors.log" <<'LOG'
 2026-09-05 12:00:00 INFO fleetd listening
@@ -753,6 +853,11 @@ test_drain_gate_refusal_build_ran_staged_present
 test_drain_gate_refusal_build_ran_staged_absent
 test_drain_gate_refusal_no_build_staged_present
 test_drain_gate_refusal_no_build_staged_absent
+test_refuse_drain_gate_build_ran_staged_present
+test_refuse_drain_gate_build_ran_staged_absent
+test_refuse_drain_gate_no_build_staged_present
+test_refuse_drain_gate_no_build_staged_absent
+test_refuse_drain_gate_call_site_present
 test_no_errors
 test_recovery_patterns_match_source
 test_attributed_recovered_connection_error