Merge #520: pin the drain-gate abort branch and jar_id's absent case (fleetd #517)

Verified by the lead, not taken from the worker's report:

- 40 test functions defined, 40 invoked (my own greps), suite exit 0, zero real FAIL lines.
- Harness proof on my own invocation: re-applying the jar_id absent->present mutation gives
  exit 1 and "FAIL: jar_id with no arguments must report absent when $JAR does not exist".
  So a green run from this suite is readable.
- Script restored byte-identical after every mutation:
  2cb83dc380c7226191d657c40fccdfc856904e40b2d03d0851fb6e522cee2f41.
- drain_gate_refusal is pure and prints only; die() stays outside the command substitution, so
  the "die inside $( ) exits only the subshell" trap does not apply here.
- The --no-build + staged-present case reads "nothing changed" deliberately, and that is correct:
  --no-build stages nothing itself, and a leftover staged jar is wiped by rm -f "$JAR_STAGED"
  at :607, before the build at :610.

The worker's out-of-scope finding is real and I reproduced it: the swap guard at :723 can be set
to `if false` with the suite still green at exit 0. Filed separately.

scripts/redeploy-fleetd.sh

@@ -452,6 +452,35 @@ classify_amqp_connection_errors() {
   REDEPLOY_UNEXPLAINED_ERRORS=$((REDEPLOY_UNEXPLAINED_ERRORS + pending_inbox + pending_lead_mailbox))
 }
 
+# fleetd #517: extracted so the suite can call this decision directly, the same way #510 extracted
+# wait_for_daemon_exit so its ordering became checkable. Before this, the only test of the drain-gate
+# abort message was a grep of this script's own source for the wording — so mutating the `if` below
+# to `if false` (making the branch unreachable) left every test green, because the wording was still
+# sitting in the file. Pure: only decides which message applies and prints it, no side effects, so a
+# test can call it directly with an in-memory staged path instead of driving the real drain-gate flow
+# (which needs a live $OLD_PID and an interactive prompt neither test can supply).
+#
+# The four cases:
+#   build ran,  staged jar present -> names the staged jar and how to finish or discard it
+#   build ran,  staged jar absent  -> "nothing changed" (nothing was staged this run either)
+#   --no-build, staged jar present -> ALSO "nothing changed", deliberately: --no-build itself builds
+#     and stages nothing (see require_no_build_jar above), so a staged jar found here is a leftover
+#     from an earlier, unrelated run. THIS run truly changed nothing, and the next DO_BUILD=1 run
+#     wipes that leftover before it builds (`rm -f "$JAR_STAGED"` in the build section above) — so
+#     there is nothing here for the operator to lose track of.
+#   --no-build, staged jar absent  -> "nothing changed"
+drain_gate_refusal() {
+  local do_build="$1" staged_path="$2"
+  if [ "$do_build" = 1 ] && [ -f "$staged_path" ]; then
+    printf 'aborted — the running daemon was NOT touched, but the freshly built jar is sitting at
+        %s, not yet swapped into %s. Rerun WITHOUT --no-build to finish the restart —
+        the freshly built jar is no longer at the live path that --no-build requires — or
+        remove %s by hand if you want to discard this build.' "$staged_path" "$JAR" "$staged_path"
+  else
+    printf 'aborted — nothing changed'
+  fi
+}
+
 # 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
@@ -610,16 +639,10 @@ 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: "nothing changed" would be a lie once a build has run — the freshly built jar
+    # fleetd #493 / #517: "nothing changed" would be a lie once a build has run and staged a jar —
-    # already moved to $JAR_STAGED (stage_built_jar, above), so the live path has one fewer file
+    # see drain_gate_refusal above for the full decision and why each of its four cases reads the
-    # than before this run started, even though the running daemon itself was never touched.
+    # way it does.
-    if [ "$DO_BUILD" = 1 ] && [ -f "$JAR_STAGED" ]; then
+    die "$(drain_gate_refusal "$DO_BUILD" "$JAR_STAGED")"
-      die "aborted — the running daemon was NOT touched, but the freshly built jar is sitting at
-          $JAR_STAGED, not yet swapped into $JAR. Rerun WITHOUT --no-build to finish the restart —
-          the freshly built jar is no longer at the live path that --no-build requires — or
-          remove $JAR_STAGED by hand if you want to discard this build."
-    fi
-    die "aborted — nothing changed"
   fi
 fi
 

scripts/test-redeploy-fleetd.sh

@@ -228,6 +228,24 @@ test_jar_id_defaults_to_live_and_reports_explicit_path() {
   assert_equals "$staged_hash" "$explicit_result" "jar_id \"\$JAR_STAGED\" must report the hash of the staged jar, not fall back to \$JAR"
 }
 
+# fleetd #517 — jar_id()'s "absent" branch was unpinned by any test: the existing test above (#511)
+# proves both halves of the present-file contract but never exercises the missing-file path. This
+# word matters more than a string usually would: "absent" is the #413 signal that a `mvn clean`
+# deleted the running daemon's jar out from under it, and the `redeploy-fleetd` skill points
+# operators at `--check` for exactly this. Covers both the no-argument default and an explicit path,
+# since the mutation (`absent` -> `present`) sits on the single shared `|| echo` and would flip both.
+test_jar_id_reports_absent_for_missing_file() {
+  local saved_jar="$JAR" dir default_result explicit_result
+  dir="$TMP/jar-id-absent"; mkdir -p "$dir"
+  JAR="$dir/does-not-exist.jar"
+  [ ! -f "$JAR" ] || fail "test fixture error: \$JAR unexpectedly exists at $JAR"
+  default_result="$(jar_id)"
+  explicit_result="$(jar_id "$dir/also-does-not-exist.jar")"
+  JAR="$saved_jar"
+  assert_equals "absent" "$default_result" "jar_id with no arguments must report absent when \$JAR does not exist"
+  assert_equals "absent" "$explicit_result" "jar_id with an explicit missing path must report absent"
+}
+
 # fleetd #493 — never build into the path a running process holds. stage_built_jar/swap_staged_jar
 # are exercised directly against real files on disk (not stubs), because the whole point is file
 # behavior (does the content move, does the source disappear, does a failure leave both sides
@@ -386,6 +404,54 @@ test_drain_gate_abort_message_says_no_no_build() {
     || fail "abort message does not say why --no-build cannot finish the restart"
 }
 
+# fleetd #517 — the drain-gate abort branch itself. Before this, the only test of this message was
+# a source-text grep (test_drain_gate_abort_message_says_no_no_build, below): it greps this script's
+# own file for the wording, which stays in the file even if the `if` guarding it is mutated to
+# `if false` and the branch can never run. These four tests call drain_gate_refusal directly instead,
+# so they fail if the branch is unreachable OR if its wording regresses — the grep test is KEPT
+# alongside these, not replaced, because it catches a different regression (a re-wording that still
+# reaches the right branch would not change which case fires here, but would still be worth pinning).
+test_drain_gate_refusal_build_ran_staged_present() {
+  local dir staged result
+  dir="$TMP/drain-refusal-build-staged"; mkdir -p "$dir"
+  staged="$dir/fleetd-new.jar"
+  printf 'staged jar bytes' > "$staged"
+  result="$(drain_gate_refusal 1 "$staged")"
+  printf '%s' "$result" | grep -qF "$staged" \
+    || fail "build-ran+staged-present refusal does not name the staged jar path"
+  printf '%s' "$result" | grep -qF 'Rerun WITHOUT --no-build' \
+    || fail "build-ran+staged-present refusal does not tell the operator how to finish the restart"
+  if printf '%s' "$result" | grep -qF 'nothing changed'; then
+    fail "build-ran+staged-present refusal must not claim nothing changed — the jar already moved"
+  fi
+}
+
+test_drain_gate_refusal_build_ran_staged_absent() {
+  local dir result
+  dir="$TMP/drain-refusal-build-no-staged"; mkdir -p "$dir"
+  result="$(drain_gate_refusal 1 "$dir/fleetd-new.jar")"
+  assert_equals "aborted — nothing changed" "$result" "build-ran+staged-absent refusal wording"
+}
+
+# --no-build itself never builds or stages anything (require_no_build_jar, above), so a staged jar
+# found here is a leftover from an earlier, unrelated run — THIS run truly changed nothing. See the
+# comment above drain_gate_refusal in redeploy-fleetd.sh for the full reasoning.
+test_drain_gate_refusal_no_build_staged_present() {
+  local dir staged result
+  dir="$TMP/drain-refusal-no-build-staged"; mkdir -p "$dir"
+  staged="$dir/fleetd-new.jar"
+  printf 'leftover staged jar bytes' > "$staged"
+  result="$(drain_gate_refusal 0 "$staged")"
+  assert_equals "aborted — nothing changed" "$result" "no-build+staged-present refusal must deliberately say nothing changed"
+}
+
+test_drain_gate_refusal_no_build_staged_absent() {
+  local dir result
+  dir="$TMP/drain-refusal-no-build-no-staged"; mkdir -p "$dir"
+  result="$(drain_gate_refusal 0 "$dir/fleetd-new.jar")"
+  assert_equals "aborted — nothing changed" "$result" "no-build+staged-absent refusal wording"
+}
+
 test_no_errors() {
   cat > "$TMP/no-errors.log" <<'LOG'
 2026-09-05 12:00:00 INFO fleetd listening
@@ -598,6 +664,7 @@ test_count_daemon_pids
 test_assert_single_daemon_accepts_one_pid
 test_assert_single_daemon_rejects_two_pids
 test_jar_id_defaults_to_live_and_reports_explicit_path
+test_jar_id_reports_absent_for_missing_file
 test_stage_built_jar_moves_off_live_path
 test_stage_built_jar_dies_when_build_produced_nothing
 test_swap_staged_jar_moves_staged_onto_live
@@ -609,6 +676,10 @@ test_wait_for_daemon_exit_returns_true_once_pid_clears
 test_wait_for_daemon_exit_times_out_if_pid_never_clears
 test_swap_ordered_after_wait_and_before_start
 test_drain_gate_abort_message_says_no_no_build
+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_no_errors
 test_recovery_patterns_match_source
 test_attributed_recovered_connection_error