#!/usr/bin/env bash
## lsphp-info-probe.test.sh — regression test for the SIGPIPE-under-pipefail
## class of bug that shipped in cac-lsphp (trunk 9343a56) and silently turned
## $_SERVER path parity off on every shared-ols site whose host lost the race.
##
## THE BUG. entrypoint-lsphp.sh asked "is cac_path_parity loaded?" with
##
##     printf '%s\n' "$LSPHP_INFO" | grep -q '^cac_path_parity support => enabled$'
##
## under `set -euo pipefail`. `grep -q` exits the instant it matches; printf is
## still pushing the rest of `lsphp -i` into the pipe, takes SIGPIPE, and exits
## 141; pipefail prefers that over grep's 0. So the test read FALSE **because
## the extension was present** — present early enough in the output to stop the
## reader — and the container fell back to the degraded auto_prepend normaliser
## the extension exists to replace, while telling the operator the extension was
## "not loadable in this image".
##
## THE RULE THIS FILE ENFORCES, stated so nobody re-derives a wrong one: ANY
## `writer | early-exiting-reader` under pipefail is a latent 141. PAYLOAD SIZE
## IS NOT A SAFETY ARGUMENT — each run is a race on whether the reader's close
## lands before the writer's final write() returns, and size only sets how many
## write() syscalls the writer must survive. Measured against a default
## 65536-byte pipe: 41144 bytes SIGPIPEd on 32/300 runs (11%, well UNDER
## capacity) and 65012 bytes on 25/30 (not certain even AT capacity); 500 KB
## into a 1 MiB pipe was 200/200 when written 4096 bytes at a time and 0/200 as
## a single write. A call site is sound only for a STRUCTURAL reason: the file
## does not set pipefail, or the reader provably consumes to EOF (no `q`, `-q`,
## `-l`, `-m`, `exit`, `break`), or the pipeline's status is discarded. Section 4
## below prints this race happening at ~41 KB; if the numbers there ever read as
## "small payloads are fine", the numbers are right and the reading is wrong.
##
## WHY THE EXISTING SUITE DID NOT CATCH IT. The .phpt suite and
## fpm-parity-check.sh both test the EXTENSION; nothing executed the
## ENTRYPOINT's branch logic, and the Dockerfile's own `lsphp -i | grep -q`
## build gate runs under `bash -c 'set -e'` with NO pipefail, so it reported the
## extension present in the very image whose entrypoint declared it missing.
##
## WHAT THIS ASSERTS.
##   1. behaviour — the SHIPPED probe helpers (extracted verbatim from
##      entrypoint-lsphp.sh, never copied, so they cannot drift) return the
##      right answer AND a clean exit status under `set -euo pipefail` with a
##      realistic ~40 KB phpinfo body.
##   2. structure — no script in this repo that enables pipefail pipes into a
##      reader that can exit before its writer finishes. This is the check that
##      fails deterministically against trunk; assertion 1's *old* form is a
##      RACE (measured 141 on 3 of 5 runs here, 5 of 5 on whp02, and 0 of 5
##      under a different Docker daemon), so no behavioural assertion about the
##      broken code could be trusted to fail on every machine. Section 4 runs
##      the old form anyway and prints what it did, for the record.
##   3. equivalence — the helpers' pure-bash matching answers exactly what the
##      grep/awk patterns they replaced answer, checked case by case against
##      those same patterns reading a FILE (a file, so the reference itself
##      cannot SIGPIPE). Section 6.
##   4. the scan's own coverage — every reader shape section 5 claims to catch
##      is caught, and a matched set of safe shapes is NOT flagged. Section 7.
##      Without this the scan's regexes are unfalsified and can quietly stop
##      matching; `grep -l` and `sed q` were both missed until section 7 existed.
##
## SCOPE LIMITS, stated rather than hidden. The structural scan is a text scan,
## so it under-reports in known ways:
##   - it reads one line at a time. The repo's only multi-line pipeline
##     (ols-htaccess-watcher.sh's `inotifywait … |` / `while read`) is invisible
##     to it and was reviewed by hand: that reader loops until EOF, i.e. until
##     the writer has already gone, so it cannot produce this failure.
##   - its quote stripping is flat, so a pipe nested inside a command
##     substitution inside a quoted string (`echo "x ($(a | head -1))"`) is read
##     as quoted text and skipped.
##   - the reader list is an ENUMERATION, not a proof. It knows `grep`
##     (-q/-l/-L/-m and their long forms), `head`, `read`, `awk … exit` and
##     `sed` with a q/Q command; it does not know an early exit hidden in
##     `perl -ne '… last'`, `python -c`, `jq`, `head -c`, or any project-local
##     program that stops reading. A reader not on the list is not thereby safe.
##   - it only inspects the FIRST word after a pipe, so `foo | LC_ALL=C grep -q`
##     or `foo | { grep -q x; }` reads as an unknown reader and is skipped.
## It is a guard against reintroducing the shape, not a proof of its absence.
##
## Usage: scripts/tests/lsphp-info-probe.test.sh [REPO_ROOT]
## Exit: 0 all assertions passed, 1 an assertion FAILED, 2 the test could not run.

set -uo pipefail

HERE="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
ROOT="${1:-$(cd "$HERE/../.." && pwd)}"
ENTRYPOINT="$ROOT/scripts/entrypoint-lsphp.sh"
TMP="$(mktemp -d)"
trap 'rm -rf "$TMP"' EXIT

pass=0; fail=0
ok()   { pass=$((pass+1)); echo "  ok   — $1"; }
bad()  { fail=$((fail+1)); echo "  FAIL — $1" >&2; }
die()  { echo "HARNESS FAILURE: $*" >&2; exit 2; }

[ -f "$ENTRYPOINT" ] || die "no entrypoint at $ENTRYPOINT (pass REPO_ROOT as \$1)"

## ---------------------------------------------------------------------------
## 1. Extract the real probe helpers. Not a copy: whatever the shipped
##    entrypoint says between the markers is what runs below, so a future edit
##    that reintroduces a pipeline is tested, not narrated.
##
##    A missing block is an assertion FAILURE, not a harness error, and it does
##    not stop the run: against a pre-fix checkout the probes are still inline
##    pipelines, and section 5 below is what names them. Bailing out here would
##    have replaced that report with "could not run".
##
##    BOUNDED ON PURPOSE. The extraction buffers and emits NOTHING until it has
##    seen the END marker, so deleting or mistyping that one line is a marker
##    error (exit 4) rather than a slurp of every line after BEGIN into a file
##    this harness then `source`s. That is not hypothetical: it happened during
##    development and only failed loudly by luck — `set -u` tripped over an
##    unbound variable two statements into the entrypoint's real boot code. An
##    extractor whose failure mode is "execute arbitrary parts of the program
##    under test" is not a safe thing to leave lying around, however careful the
##    markers are today.
##      exit 0 = both markers, block on stdout
##      exit 3 = no BEGIN marker at all (pre-fix checkout, or block removed)
##      exit 4 = BEGIN seen, END missing — refuse to emit, refuse to source
## ---------------------------------------------------------------------------
HAVE_HELPERS=yes
XRC=0
awk '
  /^## ---- CAC-TEST: probe helpers BEGIN ----$/ { f = 1 }
  f { buf = buf $0 ORS }
  f && /^## ---- CAC-TEST: probe helpers END ----$/ { printf "%s", buf; found = 1; exit 0 }
  END { if (found) exit 0; else if (f) exit 4; else exit 3 }
' "$ENTRYPOINT" > "$TMP/helpers.sh" || XRC=$?

case "$XRC" in
  0)
    for fn in lsphp_info_has_parity_ext lsphp_info_scan_dir lsphp_info_is_usable; do
      if ! grep -q "^${fn}()" "$TMP/helpers.sh"; then
        HAVE_HELPERS=no
        bad "the probe-helper block in ${ENTRYPOINT#"$ROOT"/} defines no ${fn}()"
      fi
    done
    ;;
  4)
    HAVE_HELPERS=no
    : > "$TMP/helpers.sh"
    bad "${ENTRYPOINT#"$ROOT"/} has a 'CAC-TEST: probe helpers BEGIN' marker with no matching END marker. Nothing was extracted — an unterminated block would otherwise have pulled the whole rest of the entrypoint into a file this test sources and runs."
    ;;
  3)
    HAVE_HELPERS=no
    bad "no probe-helper markers in ${ENTRYPOINT#"$ROOT"/} — either they were removed, or this is a pre-fix checkout where the probes are still inline pipelines (trunk 9343a56). Section 5 says which lines."
    ;;
  *)
    HAVE_HELPERS=no
    bad "extracting the probe-helper block from ${ENTRYPOINT#"$ROOT"/} failed (awk exit $XRC)"
    ;;
esac

## ---------------------------------------------------------------------------
## 2. Fixtures. Shaped like real `lsphp -i`: the two lines the probes look for
##    sit near the TOP (that is what lets a reader stop early), with tens of KB
##    of body after them. A fixture whose marker is near the end could not
##    SIGPIPE at all and would make this whole test vacuous, so both properties
##    are asserted before anything else runs.
## ---------------------------------------------------------------------------
SCAN_PATH='/usr/local/lsws/lsphp83/etc/php/8.3/mods-available'
make_fixture() {  # $1=outfile  $2=yes|no (include the cac_path_parity line)
  {
    printf 'phpinfo()\nPHP Version => 8.3.27\n\n'
    printf 'System => Linux 6ecb4e0a1c1f 5.15.0 #1 SMP x86_64\n'
    printf 'Server API => LiteSpeed V8.3\n'
    printf 'Configuration File (php.ini) Path => /usr/local/lsws/lsphp83/etc/php/8.3/litespeed\n'
    printf 'Scan this dir for additional .ini files => %s\n' "$SCAN_PATH"
    printf 'PHP API => 20230831\nDebug Build => no\nThread Safety => disabled\n\n'
    printf 'bcmath\n\nBCMath support => enabled\n\n'
    printf 'calendar\n\nCalendar support => enabled\n\n'
    [ "$2" = yes ] && printf 'cac_path_parity\n\ncac_path_parity support => enabled\nRewriting => active\n\n'
    printf 'Core\n\nPHP Version => 8.3.27\n\n'
    ## ~40 KB of directive rows, exactly the shape phpinfo() prints them in.
    local i=0
    while [ "$i" -lt 700 ]; do
      printf 'some.directive_%03d => local_value_%03d => master_value_%03d\n' "$i" "$i" "$i"
      i=$((i+1))
    done
  } > "$1"
}
make_fixture "$TMP/info-present.txt" yes
make_fixture "$TMP/info-absent.txt"  no
: > "$TMP/info-empty.txt"

echo "== fixture sanity =="
FIX_BYTES=$(wc -c < "$TMP/info-present.txt")
MATCH_OFF=$(grep -b -m1 '^cac_path_parity support => enabled$' "$TMP/info-present.txt" | cut -d: -f1)
if [ "$FIX_BYTES" -ge 32768 ]; then
  ok "fixture is ${FIX_BYTES} bytes (realistic 'lsphp -i' is ~40 KB)"
else
  bad "fixture is only ${FIX_BYTES} bytes — too small to reproduce the failure"
fi
if [ "$MATCH_OFF" -lt $((FIX_BYTES / 4)) ]; then
  ok "match sits at byte ${MATCH_OFF} of ${FIX_BYTES} — most of the body is still unwritten when a reader could stop"
else
  bad "match at byte ${MATCH_OFF} of ${FIX_BYTES} leaves too small a tail; the test would be vacuous"
fi

## ---------------------------------------------------------------------------
## 3. Behaviour, under the REAL option set (`set -euo pipefail`, as line 34 of
##    the entrypoint sets it). Each case runs in its own bash process so the
##    options and the exit status are the genuine article, not something this
##    harness simulated.
## ---------------------------------------------------------------------------
cat > "$TMP/runner.sh" <<'RUNNER'
#!/usr/bin/env bash
set -euo pipefail
# shellcheck disable=SC1091
source "$1"                      # the extracted probe helpers
LSPHP_INFO=$(cat "$2")
case "$3" in
  has_ext)  lsphp_info_has_parity_ext "$LSPHP_INFO" ;;
  scan_dir) lsphp_info_scan_dir "$LSPHP_INFO" ;;
  usable)   lsphp_info_is_usable "$LSPHP_INFO" ;;
  legacy)   printf '%s\n' "$LSPHP_INFO" | grep -q '^cac_path_parity support => enabled$' ;;
  *) echo "unknown case $3" >&2; exit 99 ;;
esac
RUNNER

## NOT `out=$(run …)`: command substitution runs the function in a subshell,
## where an exit status assigned to RC would be thrown away with it. Run in this
## shell, capture stdout through a file, and RC is the real thing.
RC=0; out=""
run() {  # $1=fixture $2=case -> sets RC and out
  RC=0
  bash "$TMP/runner.sh" "$TMP/helpers.sh" "$1" "$2" >"$TMP/out" 2>&1 || RC=$?
  out=$(cat "$TMP/out")
}

echo "== the shipped probes under set -euo pipefail =="
if [ "$HAVE_HELPERS" = no ]; then
  echo "  (skipped — no probe helpers to run; see the failure above)"
fi
if [ "$HAVE_HELPERS" = yes ]; then

run "$TMP/info-present.txt" has_ext
if [ "$RC" -eq 0 ]; then
  ok "extension present => branch TAKEN (exit 0)"
elif [ "$RC" -eq 141 ]; then
  bad "exit 141 (SIGPIPE): the probe is a pipeline again — this is the original bug"
else
  bad "extension present => exit $RC (expected 0). Output: $out"
fi

run "$TMP/info-absent.txt" has_ext
if [ "$RC" -eq 1 ]; then
  ok "extension genuinely absent => branch NOT taken (exit 1, a clean 'no')"
else
  bad "extension absent => exit $RC (expected 1). Output: $out"
fi

run "$TMP/info-present.txt" scan_dir
if [ "$RC" -eq 0 ] && [ "$out" = "$SCAN_PATH" ]; then
  ok "scan-dir probe returns '$out' (exit 0)"
elif [ "$RC" -eq 141 ]; then
  bad "scan-dir probe exit 141 (SIGPIPE) — as a bare assignment under set -e that KILLS PID 1"
else
  bad "scan-dir probe => exit $RC, got '$out', expected '$SCAN_PATH'"
fi

run "$TMP/info-present.txt" usable
if [ "$RC" -eq 0 ]; then ok "usability probe: real phpinfo body => usable (exit 0)"
else bad "usability probe on real body => exit $RC (expected 0)"; fi

run "$TMP/info-empty.txt" usable
if [ "$RC" -eq 1 ]; then ok "usability probe: empty body => NOT usable (exit 1)"
else bad "usability probe on empty body => exit $RC (expected 1)"; fi

## The two failure causes must be reported as the different things they are.
## A probe that cannot answer has established nothing about the image, and the
## old message asserted the opposite of that for every reason it fired.
## SC2016: these patterns are the entrypoint's literal text, `$` and all.
# shellcheck disable=SC2016
if grep -q 'if lsphp_info_is_usable "$LSPHP_INFO"; then' "$ENTRYPOINT" &&
   grep -q 'This is a PROBE failure and establishes nothing' "$ENTRYPOINT"; then
  ok "a probe that produced nothing is reported as OUR failure, not as a verdict on the image"
else
  bad "entrypoint no longer reports an unusable 'lsphp -i' as a probe failure"
fi
# shellcheck disable=SC2016
if grep -q 'not loadable in this image' "$ENTRYPOINT" &&
   grep -q 'answered (${#LSPHP_INFO} bytes, scan dir ${SCAN_DIR}) and does not list it' "$ENTRYPOINT"; then
  ok "the 'extension not loadable' verdict now ships the evidence it rests on"
else
  bad "the 'extension not loadable' message no longer states what it observed"
fi

fi   # HAVE_HELPERS

## ---------------------------------------------------------------------------
## 4. The old form, for the record. NOT asserted: it is a race, and asserting a
##    race would make this suite flap on whichever machine happens to win it.
## ---------------------------------------------------------------------------
echo "== the pre-fix pipeline form on the same input (informational) =="
if [ "$HAVE_HELPERS" = no ]; then
  echo "  (skipped — the runner needs the helper block to source)"
fi
legacy_rcs=""
if [ "$HAVE_HELPERS" = yes ]; then
for _ in 1 2 3 4 5 6 7 8 9 10; do
  run "$TMP/info-present.txt" legacy
  legacy_rcs="$legacy_rcs $RC"
done
echo "  10 runs of 'printf | grep -q' under pipefail:${legacy_rcs}"
echo "  (0 = happened to finish writing, 141 = writer SIGPIPEd and pipefail reported the"
echo "   extension MISSING because it was present. Either value is expected here.)"
fi

## ---------------------------------------------------------------------------
## 5. Structural scan — the deterministic guard, and the part of this file that
##    fails against trunk on EVERY machine. Any script that turns on pipefail
##    and pipes into a reader that can stop early has this bug latent in it
##    whether or not today's buffer sizes expose it, so the shape is what gets
##    outlawed, not the symptom.
##
##    It is a text scan, so it is honest about its limits: it strips quoted
##    spans and comments (that is what keeps `case a|b)`, `sed "s|x|y|"` and
##    `echo "a | b"` from being reported), it requires the reader to be the
##    FIRST word after a pipe, and it reads one line at a time. This file is
##    skipped because section 4 runs the broken form on purpose.
## ---------------------------------------------------------------------------
echo "== structural scan: early-exit readers in pipefail scripts =="
mapfile -t PIPEFAIL_FILES < <(grep -rl --include='*.sh' -E '^[[:space:]]*set[[:space:]]+-[a-zA-Z]*[[:space:]]*o?[[:space:]]*pipefail|^[[:space:]]*set[[:space:]]+-o[[:space:]]+pipefail' "$ROOT/scripts" "$ROOT/ext" 2>/dev/null | sort)
[ "${#PIPEFAIL_FILES[@]}" -gt 0 ] || die "found no pipefail-enabled scripts under $ROOT — the scan would be vacuous"

cat > "$TMP/scan.awk" <<'AWKPROG'
# Does this `grep …` invocation stop reading before EOF? -q/-l/-L/-m do; -c,
# -i, -v, -o, -n and the rest read the whole input and are none of our business.
# Walked option by option rather than pattern-matched in one go, because the
# letters have to be read the way grep reads them: a cluster like -im1 stops
# early, -e/-f/-A/-B/-C/-d/-D swallow the rest of their token as an ARGUMENT
# (so `grep -eq` is the pattern "q", not --quiet), and the first non-option word
# is the pattern, after which nothing is a flag any more.
function grep_stops_early(s,    a, k, j, t, c, m) {
  if (s !~ /^[[:space:]]*grep([[:space:];&)]|$)/) return 0
  sub(/^[[:space:]]*grep([[:space:]]+|$)/, "", s)
  m = split(s, a, /[[:space:]]+/)
  for (k = 1; k <= m; k++) {
    t = a[k]
    if (t == "") continue
    if (t == "--") return 0
    if (t ~ /^--/) {
      if (t ~ /^--(quiet|silent|max-count|files-with-match|files-without-match)/) return 1
      continue
    }
    if (t !~ /^-/) return 0                    # the pattern; options are over
    sub(/^-/, "", t)
    for (j = 1; j <= length(t); j++) {
      c = substr(t, j, 1)
      if (c == "q" || c == "l" || c == "L" || c == "m") return 1
      if (c ~ /[efABCdD]/) break                # rest of the token is its argument
    }
  }
  return 0
}
{
  raw = $0
  l = raw
  gsub(/\\"/, "X", l); gsub(/\\'/, "X", l)          # escaped quotes are not delimiters
  while (match(l, /'[^']*'/)) l = substr(l, 1, RSTART-1) "SQ" substr(l, RSTART+RLENGTH)
  while (match(l, /"[^"]*"/))             l = substr(l, 1, RSTART-1) "DQ" substr(l, RSTART+RLENGTH)
  if (l ~ /^[[:space:]]*#/) next                        # whole-line comment
  sub(/[[:space:]]#.*/, "", l)                          # trailing comment

  # `u` = the line with quote CHARACTERS dropped but their contents KEPT, used
  # only to read a command's script argument. `l` cannot serve for that: it
  # replaces a whole quoted span with a placeholder, so `sed 'q'` and
  # `awk '{exit}'` lose the very token that makes them early-exit readers.
  u = raw
  gsub(/["']/, "", u)
  sub(/[[:space:]]#.*/, "", u)

  gsub(/\|\|/, " ", l)                                  # || is not a pipeline
  if (l !~ /\|/) next
  n = split(l, seg, "|")
  for (i = 2; i <= n; i++) {
    r = seg[i]
    if (grep_stops_early(r))                                        { print NR ": " raw; next }
    # The `[[:space:];&)]|$` tail rather than a bare `[[:space:]]|$`: a reader
    # can be the last word of a compound command (`… | head; }`), which the
    # whitespace-only form silently skipped.
    if (r ~ /^[[:space:]]*head([[:space:];&)]|$)/)                     { print NR ": " raw; next }
    if (r ~ /^[[:space:]]*(while[[:space:]]+)?read([[:space:];&)]|$)/) { print NR ": " raw; next }
    if (r ~ /^[[:space:]]*awk([[:space:];&)]|$)/ && u ~ /exit/)         { print NR ": " raw; next }
    # sed: a q/Q command anywhere in the script — `/re/q`, `2q`, `$q`, `1p;q`,
    # `{…;q}`, and the bare `sed q` / `sed 'q'` that the earlier pattern missed
    # (it required a `;`, `{` or `/` in front of the q, which a lone script has
    # none of). Anchored on what may PRECEDE the q and what may FOLLOW it, so a
    # q inside a replacement — `sed s/a/q/` — is not read as the command (which
    # is what the trailing `/` exclusion buys: a command q is never followed by
    # another delimiter, a replacement q always is).
    if (r ~ /^[[:space:]]*sed([[:space:];&)]|$)/ &&
        (u ~ /[;{\/][[:space:]]*[qQ]([^[:alnum:]\/]|$)/ ||
         u ~ /[[:space:]]([0-9]+|\$)?[qQ]([[:space:];}]|$)/))       { print NR ": " raw; next }
  }
}
AWKPROG

offenders=0
for f in "${PIPEFAIL_FILES[@]}"; do
  [ "$(basename "$f")" = "$(basename "${BASH_SOURCE[0]}")" ] && continue
  while IFS= read -r hit; do
    offenders=$((offenders+1))
    echo "  FAIL — ${f#"$ROOT"/}:${hit}" >&2
  done < <(awk -f "$TMP/scan.awk" "$f")
done
if [ "$offenders" -eq 0 ]; then
  ok "${#PIPEFAIL_FILES[@]} pipefail-enabled scripts, no pipeline whose reader can outrun its writer"
else
  bad "$offenders pipeline(s) above pipe into an early-exit reader under pipefail."
  echo "       Read the value into a variable and match it in the shell (see" >&2
  echo "       lsphp_info_has_parity_ext in scripts/entrypoint-lsphp.sh), or give the" >&2
  echo "       reader the file directly. Neither is a pipeline, so there is no second" >&2
  echo "       exit status for pipefail to prefer. A here-string also works, but it" >&2
  echo "       spills to a temp file above a build-dependent size, so it is not the" >&2
  echo "       right shape on a boot path." >&2
fi

## ---------------------------------------------------------------------------
## 6. Equivalence. The helpers answer with `[[ ]]` and `${…}` what they used to
##    answer with grep and awk, and "same patterns, different plumbing" is a
##    claim that has to be checked rather than asserted — an anchored line match
##    re-expressed as a glob is exactly where an off-by-one lives.
##
##    The reference runs the ORIGINAL grep/awk patterns over a FILE, so the
##    reference itself cannot SIGPIPE and cannot be accused of the bug it is
##    refereeing. The file is written the way the old pipeline fed them,
##    `printf '%s\n' "$SUBJECT"`, so the comparison is against the pre-fix
##    behaviour byte for byte and not against a tidier reading of it.
## ---------------------------------------------------------------------------
echo "== pure-bash matching vs the grep/awk patterns it replaced =="
if [ "$HAVE_HELPERS" = no ]; then
  echo "  (skipped — no probe helpers to compare)"
else
  # shellcheck disable=SC1091
  source "$TMP/helpers.sh"

  NL=$'\n'
  eq_fail=0
  eq_case() {   # $1 = label, $2 = subject
    local label="$1" subj="$2" f="$TMP/eq.txt"
    local ref_has ref_use new_has new_use ref_scan new_scan
    printf '%s\n' "$subj" > "$f"

    ref_has=0; grep -q '^cac_path_parity support => enabled$' "$f" || ref_has=$?
    new_has=0; lsphp_info_has_parity_ext "$subj"                   || new_has=$?
    ref_use=0; grep -q '^PHP Version => ' "$f"                     || ref_use=$?
    new_use=0; lsphp_info_is_usable "$subj"                        || new_use=$?
    ref_scan=$(awk -F'=> ' '/^Scan this dir/ {print $2; exit}' "$f")
    new_scan=$(lsphp_info_scan_dir "$subj")

    if [ "$ref_has" = "$new_has" ] && [ "$ref_use" = "$new_use" ] && [ "$ref_scan" = "$new_scan" ]; then
      ok "equivalent on: $label"
    else
      eq_fail=$((eq_fail+1))
      bad "NOT equivalent on: $label — has_ext grep=$ref_has bash=$new_has; usable grep=$ref_use bash=$new_use; scan_dir awk='$ref_scan' bash='$new_scan'"
    fi
  }

  SD='Scan this dir for additional .ini files'
  PARITY='cac_path_parity support => enabled'
  eq_case "empty subject"                 ""
  eq_case "match on the first line"       "${PARITY}${NL}tail line"
  eq_case "match on the last line"        "head line${NL}${PARITY}"
  eq_case "match is the only line"        "${PARITY}"
  eq_case "match sandwiched"              "a${NL}${PARITY}${NL}b"
  eq_case "not at line start (decoy)"     "x ${PARITY}${NL}b"
  eq_case "trailing space defeats the \$" "${PARITY} ${NL}b"
  eq_case "prefix-only line (decoy)"      "cac_path_parity support => enabled but no${NL}b"
  eq_case "genuinely absent"              "a${NL}b${NL}c"
  eq_case "embedded blank lines"          "a${NL}${NL}${PARITY}${NL}${NL}b"
  eq_case "banner first, scan dir second" "PHP Version => 8.3.27${NL}${SD} => /a/b"
  eq_case "scan dir on the first line"    "${SD} => /a/b${NL}PHP Version => 8.3.27"
  eq_case "scan dir on the last line"     "PHP Version => 8.3.27${NL}${SD} => /a/b"
  eq_case "scan dir, second separator"    "${SD} => /a => /b${NL}x"
  eq_case "scan dir, empty value"         "${SD} => ${NL}x"
  eq_case "scan dir, no separator"        "Scan this dir is broken${NL}x"
  eq_case "scan dir, first of two wins"   "${SD} => /first${NL}${SD} => /second"
  eq_case "scan dir, value has spaces"    "${SD} =>  /a b/c ${NL}x"
  eq_case "scan-dir line is a prefix"     "Scan this directory => /a/b${NL}x"
  eq_case "banner not at line start"      "x PHP Version => 8.3.27${NL}b"
  eq_case "banner without trailing space" "PHP Version =>${NL}b"
  eq_case "CR-terminated lines"           $'PHP Version => 8.3.27\r'"${NL}${PARITY}"$'\r'
  eq_case "glob metacharacters in body"   "*${NL}?${NL}[a-z]${NL}${PARITY}${NL}]["
  eq_case "realistic 40 KB body"          "$(cat "$TMP/info-present.txt")"
  [ "$eq_fail" -eq 0 ] || echo "  (an inequivalence here means the shipped probe now answers something the old grep/awk did not)" >&2
fi

## ---------------------------------------------------------------------------
## 7. The scan's own coverage. Section 5 only proves something if its regexes
##    actually match the shapes it claims to outlaw — an unfalsified scanner
##    reports "clean" just as loudly when it has stopped matching anything.
##    `grep -l foo` and `sed q` were both silently missed until this section
##    existed; both are asserted below, alongside the safe forms that must NOT
##    be reported, because a scanner that flags everything is no better.
## ---------------------------------------------------------------------------
echo "== the structural scan catches what it claims to =="
cat > "$TMP/scan-bad.sh" <<'BADSH'
set -euo pipefail
a() { producer | grep -q needle; }
b() { producer | grep -qx needle; }
c() { producer | grep -m1 needle; }
d() { producer | grep -im1 needle; }
e() { producer | grep -l foo; }
f() { producer | grep -L foo; }
g() { producer | grep --quiet foo; }
h() { producer | grep --files-with-matches foo; }
i() { producer | head -1; }
j() { producer | head; }
k() { producer | read -r x; }
l() { producer | while read -r x; do :; done; }
m() { producer | awk '/x/ {print; exit}'; }
n() { producer | sed q; }
o() { producer | sed 'q'; }
p() { producer | sed 2q; }
q() { producer | sed -n '1p;q'; }
r() { producer | sed -n '/x/{p;q}'; }
s() { producer | sed '$q'; }
BADSH
cat > "$TMP/scan-good.sh" <<'GOODSH'
set -euo pipefail
a() { producer | grep -c needle; }
b() { producer | grep -i needle; }
c() { producer | grep -v needle; }
d() { producer | grep -o needle; }
e() { producer | awk '{print $1}'; }
f() { producer | sed -n 's/^K=//p'; }
g() { producer | sed 's/a/q/'; }
h() { producer | sed -e 'y/abc/xqz/'; }
i() { producer | wc -l; }
j() { producer | sort -u; }
k() { producer | tail -1; }
l() { case $x in a|b) : ;; esac; }
m() { echo "a | head -1"; }
n() { echo 'x | grep -q y'; }
o() { grep -q needle <<<"$1"; }
p() { grep -q needle "$file"; }
# q() { producer | grep -q commented-out; }
r() { producer | grep -eq foo; }
GOODSH
missed=""; falsely=""; hits_bad=""
while IFS= read -r line; do
  fn=${line#*: }; fn=${fn%%(*}
  hits_bad="$hits_bad $fn"
done < <(awk -f "$TMP/scan.awk" "$TMP/scan-bad.sh")
for want in a b c d e f g h i j k l m n o p q r s; do
  case " ${hits_bad:-} " in *" $want "*) ;; *) missed="$missed $want" ;; esac
done
mapfile -t good_hits < <(awk -f "$TMP/scan.awk" "$TMP/scan-good.sh")
if [ -z "$missed" ]; then
  ok "all 19 early-exit reader shapes are reported (incl. grep -l/-L/--quiet and bare 'sed q')"
else
  bad "the scan misses these shapes in scan-bad.sh:$missed"
  awk -f "$TMP/scan.awk" "$TMP/scan-bad.sh" >&2
fi
if [ "${#good_hits[@]}" -eq 0 ]; then
  ok "18 read-to-EOF / quoted / non-pipeline forms are not reported"
else
  falsely=$(printf '%s; ' "${good_hits[@]}")
  bad "the scan false-positives on: $falsely"
fi

echo
echo "passed: $pass   failed: $fail"
[ "$fail" -eq 0 ] || exit 1
exit 0