fix(629): round-4 — require the marker at COLUMN 0, narrowing the grammar instead of patching again

Round 4 found the last false-open: markdown has a SECOND code-block form the fence stripper does not cover — indented blocks (4 spaces or a tab). A pasted indented example still self-approved: Example: Review-verdict: MERGEABLE @ <head> -> positive Adding an indented-code stripper would be the same move that produced rounds 2, 3 and 4: fixing the instance, not the class. So the grammar is narrowed instead — the marker must sit at COLUMN 0. That kills every indentation-based ambiguity at once (4-space, tab, list-nested, arbitrary indent). Cost, accepted deliberately: a verdict indented under a list item is now ignored and classifies `absent`, which asks a human. For a gate, erring toward ignoring is the safe direction. Fence detection KEEPS its leading-whitespace tolerance, because stripping more is always safe. `test_leading_indent_is_tolerated` asserted the old behaviour and is replaced by `test_falseopen_an_indented_verdict_is_not_a_verdict`, parameterised over four indent shapes and mutation-verified: restoring `^[[:space:]]*` fails all four, control green. 172 tests. Round 4 verified clean by execution: the rc plumbing fails closed for a forced failure in the inner jq, awk, grep AND the pipeline producer (rc 3/4/5/93 -> exit 2); fence-length semantics, mismatched markers, CRLF fences, 10-marker fences, blockquote fences; emoji, CRLF, a 120k line, 200 comments; NUL rejection with no JSON-encoding bypass. refs #629 Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Decisions-Edit: yes
2026-07-26 00:52:11 +02:00
parent 299e7b27af
commit 28a9d0dbfd
4 changed files with 48 additions and 11 deletions
@@ -21,10 +21,15 @@
 #
 # THE GRAMMAR (deliberately strict — every relaxation here has been a false-open):
 #
-#   ^[space]* review-verdict: [space]* <TOKEN> [space]* @ [space]* <7-40 hex>
+#   ^review-verdict: [space]* <TOKEN> [space]* @ [space]* <7-40 hex>     (marker at COLUMN 0)
 #
-# - **Line-start marker.** Rejects a comment that quotes the template mid-sentence ("please post:
-#   Review-verdict: MERGEABLE @ …"), which would otherwise self-approve.
+# - **Marker at COLUMN 0** — no leading whitespace (#629). This rejects a mid-sentence quote
+#   ("please post: Review-verdict: MERGEABLE @ …"), and it also rejects markdown's *indented* code
+#   blocks (4 spaces or a tab) and anything nested in a list. Indented code is a second code-block
+#   form the fence stripper does not cover, and patching each form in turn is how three rounds of
+#   false-opens happened; requiring column 0 removes the ambiguity rather than enumerating it.
+#   The cost is that a verdict indented under a list item is ignored — it classifies `absent`, which
+#   asks a human. Erring toward ignoring is the safe direction for a gate.
 # - **Fenced code blocks are stripped first** (#629). The line-start anchor alone does not save us:
 #   inside a ``` block the marker IS at line start, so documentation showing the convention counted
 #   as a real verdict. Fence state is tracked PER COMMENT BODY so an unclosed fence in one comment
@@ -124,7 +129,7 @@ verdicts=$(printf '%s\n' "$encoded" | while IFS= read -r encoded_body; do
  # `grep` exits 1 for "no match" (normal) and >=2 for a real error. `|| true` flattened both into
  # success, so a failing reader silently produced no verdicts — `absent` — and dropped a real
  # BLOCKED verdict. Only "no match" may be tolerated.
-  found=$(printf '%s\n' "$outside" | grep -iE '^[[:space:]]*review-verdict:')
+  found=$(printf '%s\n' "$outside" | grep -iE '^review-verdict:')
  grep_rc=$?
  [ "$grep_rc" -le 1 ] || exit 5
  # An `if`, not `[ ... ] && printf`: the latter is the loop body's last command, so a final comment
@@ -144,9 +149,9 @@ fi
 # its length is checked separately. Matching `{7,40}` directly had no right boundary, so an over-long
 # or malformed token was silently TRUNCATED into a valid-looking one: `@ <40-hex-head><more hex>` and
 # `@ <40-hex-head>ZZZ` both matched their first 40 chars and graded as a verdict for head.
-FIELD_RE='^[[:space:]]*review-verdict:[[:space:]]*[A-Za-z][A-Za-z-]*[[:space:]]*@[[:space:]]*[0-9a-fA-F]+([^0-9a-zA-Z]|$)'
-POS_RE='^[[:space:]]*review-verdict:[[:space:]]*(mergeable|approved|lgtm)([[:space:]@]|$)'
-NEG_RE='^[[:space:]]*review-verdict:[[:space:]]*(blocked|not-mergeable)([[:space:]@]|$)'
+FIELD_RE='^review-verdict:[[:space:]]*[A-Za-z][A-Za-z-]*[[:space:]]*@[[:space:]]*[0-9a-fA-F]+([^0-9a-zA-Z]|$)'
+POS_RE='^review-verdict:[[:space:]]*(mergeable|approved|lgtm)([[:space:]@]|$)'
+NEG_RE='^review-verdict:[[:space:]]*(blocked|not-mergeable)([[:space:]@]|$)'

 head_pos=0; head_neg=0; stale=0; unknown=0
 while IFS= read -r line; do