test: the hand-rebuild diagnosis can no longer be silent (#1248)

CHANGELOG.md

@@ -458,6 +458,61 @@ true until the next version shipped.
 
 ### Fixed
 
+- The hand-rebuild diagnosis can no longer be silent, which is how the first
+  version of it still told the 2026-09-24 nightly nothing (#1248).
+
+  #1249 added `_hr_diagnose` to print `rebuild.log`'s tail when the rebuild
+  fails. The nightly of the same day failed on aarch64 again, with the gate
+  working -- the three dependent arms skipped with a reason instead of cascading
+  -- and **the diagnosis printing nothing at all**, because `rebuild.log` was
+  empty and the function opened with
+
+  ```sh
+    [ -s "${1:-}" ] || return 0
+  ```
+
+  So the one path the diagnosis exists for was the one path it stayed quiet on.
+
+  `_hr_diagnose` now always says something, and distinguishes the two causes,
+  because they are different failures and merging them costs the next reader the
+  night:
+
+  ```
+    ---- rebuild.log, last 20 lines ----
+    ---- rebuild.log is EMPTY (0 bytes): rebuild.sh exited
+         before its first echo ----
+    ---- rebuild.log is MISSING: the redirect never created it ----
+  ```
+
+  Two arms of selftest part 580 asserted the old silence and are replaced rather
+  than adjusted. They were provably wrong: `an empty log produces nothing rather
+  than an empty banner` and `and a log that is not there produces nothing rather
+  than an error` required exactly the behaviour that defeated the diagnosis on
+  aarch64. Four arms now require it to speak, and to name which of the two cases
+  it found.
+
+  **What the old diagnosis could not tell anyone, and this one can.** `[ -s ]`
+  is false for an empty file AND for one that is not there, so a silent
+  `_hr_diagnose` never distinguished them -- and neither did the first draft of
+  this entry, which asserted the log was empty when the only evidence was that
+  `-s` failed. The two have different causes and only one of them fits:
+
+  ```
+    EMPTY    rebuild.sh ran and wrote nothing before dying
+    MISSING  the redirect could not open its target, so bash returned 1 and
+             never ran the command at all
+  ```
+
+  Every exit in `rebuild.sh` before its first unconditional `echo` writes to
+  stderr first, and stderr is inside the same redirect, so EMPTY is not
+  something the script's control flow produces. MISSING is: measured, a failing
+  redirect returns 1, creates no file, and reports on the caller's stderr
+  rather than into the log. That matches `got [1]` and a silent diagnosis
+  exactly. Caught by @jdatcmd.
+
+  This does not explain why the aarch64 rebuild fails. It makes the next nightly
+  say which of the two it is.
+
 - A failed hand rebuild now says why, and stops the arms beneath it reporting on
   a rebuild that did not happen (#1248).
 

test/check_ledger.tsv

@@ -1430,12 +1430,14 @@ harness_selftest	570-a-checkout-test-must-ask-git	premise: the suite defines the
 harness_selftest	570-a-checkout-test-must-ask-git	premise: the sweep sees .git mentioned in the suites at all	15;16;17;18;19	never	-
 harness_selftest	570-a-checkout-test-must-ask-git	the sweep matches every spelling that stats .git as a directory	15;16;17;18;19	2026-09-23	the same planted line, read by the pattern shipped in #1224;the sweep pattern shipped in #1224 is restored verbatim
 harness_selftest	570-a-checkout-test-must-ask-git	without the trailing boundary the same pattern flags three of them	15;16;17;18;19	2026-09-23	the boundary in the sweep pattern drifts, so the strip becomes a no-op;the derived control stops stripping the boundary
+harness_selftest	580-a-hand-rebuild-must-record	a log that is not there also produces a diagnosis	15;16;17;18;19	2026-09-24	_hr_diagnose restored to its silent `[ -s ] || return 0` form, so an empty or missing rebuild.log prints nothing at all
 harness_selftest	580-a-hand-rebuild-must-record	a log with content produces a diagnosis to print	15;16;17;18;19	2026-09-24	rebuild.sh forced to fail after its stamp AND _hr_diagnose gutted, so the failure prints no reason
 harness_selftest	580-a-hand-rebuild-must-record	a rebuild that failed skips them rather than reading a stamp it did not write	15;16;17;18;19	2026-09-24	 driven alone, with no forced rebuild failure, because these two arms call the gate with literals and the rebuild's status never reaches them;the gate reverted so a failed rebuild still runs the arms beneath it
 harness_selftest	580-a-hand-rebuild-must-record	a rebuild that succeeded runs the arms that read its stamp	15;16;17;18;19	2026-09-24	the gate always skips, so a successful rebuild runs none of the arms that read its stamp
-harness_selftest	580-a-hand-rebuild-must-record	an empty log produces nothing rather than an empty banner	15;16;17;18;19	2026-09-24	_hr_diagnose banners unconditionally, so an empty or absent log still prints
-harness_selftest	580-a-hand-rebuild-must-record	and a log that is not there produces nothing rather than an error	15;16;17;18;19	2026-09-24	_hr_diagnose banners unconditionally, so an empty or absent log still prints
 harness_selftest	580-a-hand-rebuild-must-record	and any other status skips too, rather than being read as success	15;16;17;18;19	2026-09-24	 driven alone, with no forced rebuild failure, because these two arms call the gate with literals and the rebuild's status never reaches them;the gate reverted so a failed rebuild still runs the arms beneath it
+harness_selftest	580-a-hand-rebuild-must-record	an empty log still produces a diagnosis, because silence is the bug	15;16;17;18;19	2026-09-24	_hr_diagnose restored to its silent `[ -s ] || return 0` form, so an empty or missing rebuild.log prints nothing at all
+harness_selftest	580-a-hand-rebuild-must-record	and it distinguishes missing from empty, so the two causes do not merge	15;16;17;18;19	2026-09-24	_hr_diagnose restored to its silent `[ -s ] || return 0` form, so an empty or missing rebuild.log prints nothing at all
+harness_selftest	580-a-hand-rebuild-must-record	and it names the log as empty rather than printing a bare banner	15;16;17;18;19	2026-09-24	_hr_diagnose restored to its silent `[ -s ] || return 0` form, so an empty or missing rebuild.log prints nothing at all
 harness_selftest	580-a-hand-rebuild-must-record	and it reads a different source as stale rather than fresh	15;16;17;18;19	2026-09-23	the record call removed from rebuild.sh, so no stamp is written at all
 harness_selftest	580-a-hand-rebuild-must-record	and it writes a reason, so there is something for the gate to print	15;16;17;18;19	2026-09-24	rebuild.sh exits without saying why, so the gate has nothing to print
 harness_selftest	580-a-hand-rebuild-must-record	and the diagnosis carries the failing line, not just a status	15;16;17;18;19	2026-09-24	rebuild.sh forced to fail after its stamp AND _hr_diagnose gutted, so the failure prints no reason

test/check_ledger_budget.txt

@@ -943,4 +943,47 @@ suites_not_covered 249
 # projection ones reddens exactly one arm, at exactly the residual cost.
 #
 # suites_not_covered does NOT move: catalog_plan_index is already covered.
+
+# #1248 FOLLOW-UP: THIS NUMBER DOES NOT MOVE. Four arms replace two in part 580
+# and all six are dated, so `never` is untouched. RE-ANCHORED A SECOND TIME, on
+# the main that carries #1254 (8bd5014b):
+#
+#     ledger rows     1694 - 2 + 4 = 1696
+#     part 580 rows     22 - 2 + 4 =   24
+#     dated            155 - 2 + 4 =  157
+#     never                   1539   unchanged
+#     1539 + 157 == 1696
+#
+# The delta is constant at -2 + 4; the base has now moved twice under this
+# branch -- 1673, then 1690, then 1694. Each earlier decomposition was counted
+# correctly against a tree that no longer exists, which is why they are
+# re-anchored rather than adjusted by a difference.
+#
+# THE ROWS CONFLICT, NOT JUST THIS LINE, AND UNION IS NOT THE WHOLE ANSWER.
+# I wrote on #1251 that the rows auto-merge and only the total needs resolving.
+# False, and @jdatcmd measured it: composing this branch conflicts in
+# check_ledger.tsv itself, and taking a side drops rows silently while reporting
+# a plausible total.
+#
+# BUT "UNION THE ROWS" IS ALSO NOT ENOUGH, which this rebase demonstrated.
+# A union re-added the two rows this branch deliberately DELETES, giving
+# 1698 = 1539 + 159 against a published prediction of 1696 = 1539 + 157 -- a
+# number that looks like an ordinary miscount. Union the ADDITIONS, then honour
+# the DELETIONS, then recount. A conflict hunk cannot tell a removed row from a
+# row the other side never had.
+#
+# THE TWO REMOVED ROWS CARRY HISTORY AND IT IS DELIBERATELY NOT TRANSFERRED.
+# `orphan-scan --prune` refused them and said to reconcile or to say in the
+# commit why the history may go. It may go because these arms are not renamed,
+# they are REVERSED. Their recorded mutation is
+#
+#     _hr_diagnose banners unconditionally, so an empty or absent log still prints
+#
+# which is exactly what the four new arms REQUIRE. Carrying it forward would
+# assert each new arm is reddened by the behaviour it demands.
+#
+# The four new rows are dated on all five majors from five separate runs, one
+# merge each, under the single mutation `_hr_diagnose` restored to its silent
+# `[ -s ] || return 0` form. 4 arms x 5 majors = 20 reds, and no other check went
+# red in any of the five logs.
 checks_never_observed_red 1539

test/selftest/580-a-hand-rebuild-must-record.sh

@@ -119,10 +119,24 @@ check_text "premise: no stamp for this prefix before the rebuild" \
 _hr_dependents() {	# _hr_dependents RC -> run|skip
 	[ "${1:-}" = 0 ] && echo run || echo skip
 }
-_hr_diagnose() {	# _hr_diagnose LOGFILE -> the tail, indented, or nothing
-	[ -s "${1:-}" ] || return 0
+_hr_diagnose() {	# _hr_diagnose LOGFILE -> the tail, or WHY there is no tail
+	# NEVER SILENT. The first version returned early on `[ -s ]`, so the
+	# 2026-09-24 nightly -- which failed with an EMPTY rebuild.log on aarch64 --
+	# printed no diagnosis at all. An absent log and an empty one are different
+	# failures: one means the redirect never opened, the other means rebuild.sh
+	# exited before its first echo. Naming which one costs a line and saves a
+	# night.
+	local _f="${1:-}"
+	if [ ! -f "$_f" ]; then
+		echo "      ---- rebuild.log is MISSING: the redirect never created it ----"
+		return 0
+	fi
+	if [ ! -s "$_f" ]; then
+		echo "      ---- rebuild.log is EMPTY (0 bytes): rebuild.sh exited before its first echo ----"
+		return 0
+	fi
 	echo "      ---- rebuild.log, last 20 lines ----"
-	tail -20 "$1" | sed 's/^/      /'
+	tail -20 "$_f" | sed 's/^/      /'
 }
 
 "$PGC_TESTDIR/rebuild.sh" "$_hr_tmp/pg_config" "$_hr_tmp/tree" >"$_hr_tmp/rebuild.log" 2>&1
@@ -165,10 +179,22 @@ check_num "a log with content produces a diagnosis to print" \
 	"$([ -n "$(_hr_diagnose "$_hr_dtmp/full.log")" ] && echo 1 || echo 0)" "1"
 check_num "and the diagnosis carries the failing line, not just a status" \
 	"$(_hr_diagnose "$_hr_dtmp/full.log" | grep -c 'UNRESOLVED SYMBOLS')" "1"
-check_num "an empty log produces nothing rather than an empty banner" \
-	"$([ -n "$(_hr_diagnose "$_hr_dtmp/empty.log")" ] && echo 1 || echo 0)" "0"
-check_num "and a log that is not there produces nothing rather than an error" \
-	"$([ -n "$(_hr_diagnose "$_hr_dtmp/nope.log" 2>/dev/null)" ] && echo 1 || echo 0)" "0"
+# THESE ARMS USED TO DEMAND SILENCE, AND THE SILENCE WAS THE DEFECT (#1248).
+# The 2026-09-24 nightly failed the premise on aarch64 with an EMPTY rebuild.log.
+# `[ -s ]` returned early, so the whole diagnosis was nothing at all -- the exact
+# outcome this part exists to prevent, reached through the arm that required it.
+# A diagnosis that can be silent is not a diagnosis. When there is no tail to
+# print it must say so, and say which of the two causes it found, because
+# "rebuild.sh wrote no reason" and "the log was never created" are different
+# failures and merging them costs the next reader the night.
+check_num "an empty log still produces a diagnosis, because silence is the bug" \
+	"$([ -n "$(_hr_diagnose "$_hr_dtmp/empty.log")" ] && echo 1 || echo 0)" "1"
+check_num "and it names the log as empty rather than printing a bare banner" \
+	"$(_hr_diagnose "$_hr_dtmp/empty.log" | grep -c 'rebuild.log is EMPTY')" "1"
+check_num "a log that is not there also produces a diagnosis" \
+	"$([ -n "$(_hr_diagnose "$_hr_dtmp/nope.log" 2>/dev/null)" ] && echo 1 || echo 0)" "1"
+check_num "and it distinguishes missing from empty, so the two causes do not merge" \
+	"$(_hr_diagnose "$_hr_dtmp/nope.log" 2>/dev/null | grep -c 'rebuild.log is MISSING')" "1"
 rm -rf "$_hr_dtmp"
 
 # AND THE REAL SCRIPT MUST LEAVE SOMETHING TO DIAGNOSE. A gate that prints a log