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docs(guards): write down the ratchet-baseline convention and its worked examples (#15897) - #15959
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Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review. 📝 WalkthroughWalkthroughThe change adds ChangesRatchet baseline guidance
Estimated code review effort: 2 (Simple) | ~10 minutes Merge Risk: ⚪ Minimal · up to This change documents ratchet baseline validation practices and links the guidance for relevant future changes. It does not alter runtime behavior or production data handling and is ready to merge. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Linked Issues checkExplanation The pull request documents the convention, the two-directions table, the set-comparison rule, and the 8-versus-26 example required by issue Resolution Complete and record independent re-derivations for file size, inline_generics, hardcoded values, commit trailers, and citations. Correct any differing baselines, including the inline_generics baseline, or explicitly split those implementation tasks into linked follow-up work before treating issue ✨ Finishing Touches🧪 Generate unit tests (beta)
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Inline comments:
In `@CLAUDE.md`:
- Line 22: Update the Rule 3 guidance in CLAUDE.md to include changes to
existing detectors or matchers alongside adding a ratchet and freezing or
regenerating a baseline, directing contributors to RATCHET_BASELINES.md for the
required independent derivation.
In `@docs/developer/RATCHET_BASELINES.md`:
- Line 158: The hardcoded-values baseline row must not claim “congruent by
construction” as an independent cross-check. Update the row to mark the ratchet
unverified, or provide independent derivation, set comparison, and boundary
evidence, including a declared boundary and guard, so it satisfies Rules 1–4.
- Around line 98-99: Update the worked example in RATCHET_BASELINES.md to
clarify that a non-empty baseline floor is appropriate only when the domain
guarantees a non-empty population. Otherwise, require both a parse-shape or
sentinel validation and an independent count of the examined scope, including
the corresponding guidance at the other referenced example.
- Around line 81-85: The evidence counts in RATCHET_BASELINES.md lack their
revision scope, file scope, and matching predicates. Update each cited
count—including 2,426, 7,087, 7,373, 5,033, 8, 4, 26, 35, 246, and 464—with
explicit metadata describing what was searched and matched, or correct the
values so the examples are reproducible.
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In `@docs/developer/RATCHET_BASELINES.md`:
- Line 91: Update the documentation near the predicate re-derivation to state
that the original detector explicitly passed re.I to re.compile, rather than
implying Python enforces predicate parity. Require the independent
implementation to reproduce both the re.I flag and the same invocation behavior.
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Both Major findings accepted. Neither is cosmetic, and the first one means the 1. Rule 6's floor is bound to the wrong thing ( The distinction the rule was reaching for is real but was stated one step too Rewritten that way the rule keeps its worked example, covers the empty-population 2. Fix: relabel that row as not independently re-derived, state the reason 3. The All three are queued rather than pushed: no worktree slot is available (8 live, |
Rule 6 replacement — the Major is correct, and here is the drop-inVerified against the landed text before agreeing. Rule 6's remedy reads "a floor asserting the baseline parsed to more than zero entries" — a floor on what the parse found, which the page's own checklist forbids six lines later:
And it fails outright for a new ratchet whose population is legitimately empty, which is the state every ratchet starts in. Replace the whole of ### 6. Give the re-derivation a known positive it must find
The instrument checking the instrument is an instrument, and it gets the same
free pass everything else on this page is about.
A re-derivation of the file-size ratchet first reported **497 over-limit files
with no baseline entry** — a catastrophic-looking finding produced by parsing
`KNOWN_LARGE` as an `ast.Assign` when it is annotated and therefore an
`ast.AnnAssign`. The parse returned zero entries, so every file read as missing.
A second attempt to count the same baseline by grep returned **501**, then
**499** on a variant — both catching docstring lines, and neither agreeing with
the AST parse's 497.
So assert a **known positive** before the output means anything: a case whose
answer you already have, which the detector must find.
assert found_control, "detector does not find the known instance — result below is meaningless"
This is not a floor on the count. A floor on the count is a claim about the
*result*, so it breaks the moment a population is legitimately empty — which is
every ratchet on the day it is introduced. A known positive is a claim about the
*instrument*, so it holds at any population size including zero, and it is the
only one of the two that distinguishes **"nothing is wrong"** from **"nothing
was measured"**.
That distinction is the whole point: *a zero from a broken detector is
indistinguishable from a clean codebase.* A count that changes when you rephrase
the question — 497, 501, 499 — was never a count, and only a fixed known case
tells you which of the three instruments to trust.
**And this is the one rule on this page a lone author can apply.** Every other
error recorded here was caught by a second party or a second method, never by
the author rereading — which is a strong argument for independent re-derivation
and a weak one for individual care, because nobody can reread their way out of a
blind spot they share with their own instrument. A known positive is different:
it is a *technique*, available to one person, and it is what turns "apply the
check to the measurement" from a diagnosis into something you can actually do.Two things I'd keep from the original that this preserves: the The checklist at the end should change in step, since it currently describes the old remedy: - [ ] Both the detector and the re-derivation have a known positive they must find before their output is readThat replaces the "non-vacuity floors bound to what was examined" line. Floors on what was examined stay correct for sweeps — rules 1 and 2, and |
… re-derivations (#15897)
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Four of the five threads addressed at Rule 6 — rewritten ( The distinction that produced the contradiction is worth stating: floors bound to Evidence table — relabelled ( Rule 5 — corrected (
Left open: the Not merging on green regardless — this PR is behind base and green CI is not |
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Inline comments:
In `@docs/developer/RATCHET_BASELINES.md`:
- Line 139: Update the empty-population statement near the ratchet introduction
guidance so it applies only to ratchets whose population is legitimately empty,
rather than asserting this for every ratchet. Preserve the documented behavior
that initial baselines may contain existing violations, including the recorded
file-size entries.
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Independent review — every number re-derived, nothing blockingI am independent of this page: I did not write, edit or commit any of it. Re-derived each cluster from the sources the predicate table names, without reading how the page arrived at them first. Every figure verifies, and the drift is uniform
Every drifting figure is off by exactly +2, and every invariant is exact. That is itself worth stating: the uniform offset shows the population figures were taken together at one commit, and the page's stated predicate — "measured against Method, so this is reproducible rather than asserted:
The occurrence-versus-commit distinction is load-bearing and the page gets it right. Rule 6 — the replacement is correct, and its justification is the part that generalisesThe known-positive control is a claim about the instrument, and the page says so explicitly: "A floor on the count is a claim about the result, so it breaks the moment a population is legitimately empty — which is every ratchet on the day it is introduced." That is exactly right and it is the reason the original was wrong. I have hit both halves this week: a floor bound to findings that relaxed as the tree improved, and a detector that returned Its worked example is honest about being self-inflicted — 497 from parsing an One addition I would make, from today: a known positive proves the detector can fire; it does not prove a given probe did what it claimed. I reported a mutation as surviving when the mutation had left the property in place — the detector was right and my probe was broken. Both directions need the check, and the page currently has only the first. The table and prose agreeFive rows — file-size, citations, commit-trailer, VerdictApprove — posted as a comment because GitHub refuses No blocking findings. The one suggestion above is additive and I would not hold the page for it. The thing I would say about the page rather than its contents: it is the first artifact I have reviewed today whose claims each carry the predicate that makes them checkable. That is why this review is a table of confirmations rather than a list of questions — every number told me how to falsify it. |
…ve it (#15926) The `rglob`->`tracked_paths` fix took `check_git_toplevel_env_scrubbed.py` to 612 against its 600 ceiling. Twelve of those lines were mine and eleven were comment: the measurement table and the reasoning about why adding `.claude` to the prune set would have been the wrong fix. That reasoning is worth keeping — it is now in the PR body and on #15926, where a reader looking for *why* will actually find it, rather than in a module where it costs a guarded budget. The ratchet is the mechanism that forces that judgement, which is the argument for having it. Not raised, deliberately. `RATCHET_BASELINES.md` merged an hour ago (#15959) and uses this ceiling as its worked example of a boundary that is declared, justified and guarded. Raising it to land a fix would have made that page's only passing example a failing one on the day it landed. Trimmed to exactly 600: - comment 11 lines -> 1 - `import pathlib` dropped; `rel.split("/")` needs no import, and git returns a POSIX relative path so the split is exact - `parts` inlined into the condition it feeds 76 passed across the affected suites, ratchet green, guard exits 0. Refs #15926, #15959, #14236
…ry (#15955) (#15962) * guard(repo): five guards walked into other checkouts of this repository (#15955) This repository keeps git worktrees INSIDE the working copy -- `.worktrees/` and `.claude/worktrees/` -- so a `REPO_ROOT.rglob(...)` reaches other checkouts of itself, at revisions nobody chose, and counts their files as the tree under test. CI WAS NEVER AFFECTED, and that is the point rather than a mitigation. CI checks out clean, so the walk and the index agree there; in a clean worktree `rglob("*.sh")` returns exactly the 216 tracked files. The failure appears only on a developer machine, which is where nobody is looking. A guard that answers differently depending on who runs it is the one thing a reach floor cannot tolerate. FIXED, each on its own terms: systemd_heredoc_expansion_test.py git ls-files (431 swept, 215 foreign) slm_frontend_publish_contract_test.py git ls-files (5,307 foreign scanned) no_duplicate_dict_keys_test.py structural (walks ON PURPOSE) pytest_testpaths_cover_..._15183_test structural (9 found, 6 foreign) slm_frontend_atomic_publish_15610_test structural `git ls-files` where the guard only needs tracked files -- it reads an index, so it cannot enter another checkout. The structural detector where a guard walks deliberately: `no_duplicate_dict_keys` derives its tree list from the filesystem SO THAT git and the filesystem can disagree, and using git there would defeat the design. A worktree's `.git` is a FILE holding a `gitdir:` pointer where the primary checkout's is a directory, so nested checkouts are detectable without a name list. Hand-written prune lists are DELETED rather than extended. Nine other guards independently carry the same four-element list, typed in one at a time, and the broken ones were the two where the copy was not finished. That is the enumeration argument measured rather than argued. A SEPARATE, PRESENT DEFECT in my own guard from #15901: `rglob("*")` descends into `node_modules` and filters afterwards, so the prune never protected the walk. Any developer with a root-owned `node_modules` got `PermissionError: .../node_modules/semver` and a red guard with no explanation. `git ls-files` never enters the directory at all. ANTI-REGRESSION GUARD, and it took four attempts because I kept writing text checks: attempt 1 `all(root in source)` both mutations SURVIVED attempt 2 `'".git"' in source and "is_file()"` both mutations SURVIVED attempt 3 per-function scoping flagged 9 CORRECT guards attempt 4 literals per module, calls per function all four mutations caught The text checks were satisfied by the files' own PROSE -- my docstrings contain "git ls-files", and an unrelated `entry.is_file()` satisfied the other. A detector keyed on text is satisfied by writing about the detector. It now reads the AST: an actual `subprocess` call for git, an actual `.is_file()`/`isfile()` call naming `.git` for the structural test, and prune names from real collection literals rather than from anywhere in the source. Scoping is split because the two live at different levels: `git ls-files` is checked in the WALKING FUNCTION, since one elsewhere in the file says nothing about this walk; prune literals and the structural helper are checked against the MODULE, because both are module-level by convention and requiring them inline flagged nine correct guards. The detector reports `rglob`/`iterdir`/`os.walk` only. Including single-level `glob` produced three false positives on guards that glob an anchored pattern and cannot descend into a nested checkout at all. Verified by mutation (baseline 6 passed): revert systemd to a bare rglob 1 failed drop the structural prune from #15913 1 failed remove .claude from a correct guard 1 failed revert publish_contract to rglob 1 failed 57 passed, 1 skipped across all six files. Ceilings rc=0 after black and isort. Closes #15955 * guard(repo): the detector could not see os.walk(ROOT), and filtering is not pruning (#15955) Two Major review findings, both correct, and the first is the sharper. THE DETECTOR NAMED A CALL SHAPE IT COULD NOT SEE. `_WALK_ATTRS` has included `walk` since the first draft, but the check keyed on the RECEIVER being a root name: REPO_ROOT.rglob(...) receiver IS the root -> found os.walk(REPO_ROOT) receiver is `os` -> MISSED So a guard written to catch walks into other checkouts was blind to the most common way of writing one. That is the defect this file exists to find, in the file itself -- the fourth variant of it today, after the two text checks and the file-level scoping. Now matched on the argument shape as well, with a fixture that trips it and a contrast (`os.walk(_ANSIBLE_ROOT)`) that does not. reintroduce os.walk(REPO_ROOT) 1 failed (previously: invisible) FILTERING AFTER A WALK IS NOT PRUNING. Three functions applied the nested-checkout test to `rglob`'s RESULTS. The results were then correct, but `rglob` had already descended into `.claude/worktrees/` -- so the traversal cost was paid, and an unreadable directory it meant to skip could still abort the sweep. That is exactly the `PermissionError` this PR fixes elsewhere, unfixed in three more places. pytest_testpaths_cover_..._15183 _pytest_inis -> git ls-files pytest_testpaths_cover_..._15183 _dirs_holding_tests -> git ls-files slm_frontend_atomic_publish_15610 _nginx_files -> git ls-files `_dirs_holding_tests` is the one worth naming: it is `_pytest_inis`' SIBLING IN THE SAME FILE, it had no nested-checkout check at all, and my first fix corrected only the function the measurement had pointed at. Fixing the reported instance and leaving its neighbour is the pattern this session keeps producing; this is my fourth. `git ls-files` rather than a prune-before-descent walk, because it reads an index and never descends at all -- there is nothing to prune. 57 passed, 1 skipped across all six files. Ceilings rc=0 after black and isort. * guard(repo): two more shapes the detector named and could not reach (#15955) Both Major, both correct, and the first is the worst site found on this issue. RECURSIVE `glob("**/…")` ON A ROOT PARAMETER. `check_ci_system_package_provisioning._test_files` does `root.glob("**/*_test.py")` three times, and `audit_provisioning(root=None)` defaults `root` to the repo root. Measured: **4,644 test files reached, 3,251 of them -- 70% -- belonging to other checkouts of this repository.** Its exclusion list is `{"node_modules", "__pycache__"}`. Its docstring already discusses `.worktrees/`, which is what made it look considered: it explains why the filter is RELATIVE to `root`, a different concern entirely. Prose about a hazard is not a defence against it -- the third time on this branch that documentation has stood in for a fix. Now `_scan_helpers.tracked_paths()`, not a direct `git ls-files`: `autobot_shared` is not importable when the module runs as a bare script from the repo root, which is how the required check invokes it (#15914's trap, hit again). `os.walk(top=REPO_ROOT)`. `node.args` excludes keyword arguments, so the keyword form was invisible. Now reads `node.keywords` for `top` as well. AND THE DETECTOR NAMED A SHAPE IT FILTERED OUT FIRST -- again. Adding the `glob` branch changed nothing, because `if node.func.attr not in _WALK_ATTRS: continue` drops every `glob` call BEFORE reaching it. Second instance of this exact defect in this file: the first was `walk` listed in `_WALK_ATTRS` while the check keyed on the receiver. Two consequences of admitting `glob`, both found by running it: * the RECEIVER branch then claimed anchored globs, flagging three correct guards (`deployed_workspace_packages`, `ambient_git_vars_mirror`, `comment_line_number_citations`). `glob` is now excluded from that branch -- it is recursive only with `**`, which the dedicated branch requires; * every finding appeared TWICE, because `ast.walk(Module)` already descends into every function and `_sweep` scopes per function as well. De-duplicated. Verified by mutation (baseline 12 passed): revert the provisioning guard to root.glob("**/…") 1 failed replace a git block with os.walk(top=_REPO_ROOT) 1 failed The second mutation SURVIVED on its first attempt -- it replaced only the return statement and left the `subprocess.run(["git", "ls-files", …])` above it, so the file still read as git-sourced. That was the mutation being wrong, not the detector; re-run against the whole block it fails. A surviving mutant is a claim to check, not a result to report. 61 passed, 1 skipped across all six guard files. The provisioning audit runs clean as a script. Ceilings rc=0 after black and isort. * guard(repo): detect `glob(pattern=...)`, the keyword form (#15962) `Path.glob`'s `pattern` is positional-or-keyword, so `root.glob(pattern="**/*.py")` recurses exactly as the positional form does. The detector read only `node.args[0]`, so it saw one and missed the other. This is the same keyword blind spot I had already fixed one branch above, for `os.walk(top=...)` — fixed for that call shape and not for its neighbour, which is the miss the guard itself was written about. Two fixtures, positive and contrast: - `root.glob(pattern="**/*_test.py")` is reported - `root.glob(pattern="*.py")` is NOT — the keyword branch keeps the `**` restriction rather than routing around it. Without the contrast, "handle the keyword form" would be satisfied by flagging every keyword glob in the tree. Mutation-proven against a 14-passed baseline: - revert to `args[0]`-only -> 1 failed - keyword branch bypasses the `**` check -> 1 failed - keyword name typo'd to "patternx" -> 1 failed The tree sweep still passes, so nothing in the repository uses the shape today; this closes the hole rather than reporting a new violation. Refs #15962, #15955 * fix(guards): the git conversion broke non-git trees, and a git call excused a separate walk (#15962) Two defects, both from this branch, both found by CI shard 10/12 and review rather than by me. **1. `audit_provisioning` is also pointed at synthetic trees.** Converting `_test_files` to `tracked_paths` made it ask git, and six tests build a tree under `tmp_path` and audit it — not a checkout, no index, so git raised and the shard went red. The strict helper stays strict (#15176): a directory that is not inside a work tree is walked instead, and the branch is chosen by asking git WHERE IT IS, never by catching the failure — catching would also swallow a real git error in a real checkout and hand back a walk of 4,644 files as if it were fine. The fallback prunes both nested roots, so it cannot become a way back into the defect git was adopted for. **2. A `git ls-files` call excused every walk in the same function.** Reading the index and walking the tree are different acts; a function may do both, and `_enumerates_through_git` excused the pair. Presence of the right call is not absence of the wrong one. Removing it flagged nothing new — it was protecting no guard while covering that hole. Also: the stdlib allowlist in `test_the_checker_needs_no_third_party_import` was a literal set of five names, so it failed on `os` and `subprocess` — both stdlib. It now asks `sys.stdlib_module_names`, and a second test keeps the one repo-local exemption honest by asserting `_scan_helpers` itself reaches no further than stdlib and `autobot_shared`. Two mutations survived the first attempt at each fix, and both are worth recording: - The contrast for the exemption was written against `root_walks_in`, which never consults `_is_safe`. It passed identically with the exemption restored. A contrast written at the wrong layer cannot see the change it is for. - The first "real checkout uses git" test compared ABSOLUTE paths and reported 2,239 strays in a clean tree, because this checkout itself lives under `.worktrees/`. `_test_files`'s own docstring warns about exactly that (#14550), two functions above. The property that actually separates git from a pruned walk is untracked files, so the test now creates one and asserts its absence. Mutation-proven: | mutation | result | |---|---| | never fall back (the original red) | 6 failed | | always fall back, git never used | 1 failed | | fallback stops pruning nested roots | 1 failed | | restore the coarse git exemption | 1 failed | | excuse nothing, over-flagging correct guards | 2 failed | 21 passed and 16 passed at baseline for the two suites. Refs #15962, #15955, #15176, #14550 * fix(guards): the shell scan read 219 files from other checkouts (#15926) `check_git_toplevel_env_scrubbed.iter_shell_files` enumerated with `repo_root.rglob("*.sh")` while its Python sibling `iter_python_files` used `tracked_paths`. That asymmetry was the bug. Measured in the main checkout: | enumeration | files | in another checkout | |---|---|---| | `rglob("*.sh")` | 431 | **219 (51%)** | | `tracked_paths(root, "*.sh")` | 216 | 0 | A full-repo run reported **7 findings, every one in another checkout and none in this tree** — a pre-commit gate red for reasons outside the repository. `EXCLUDED_DIR_NAMES` names `.worktrees` but not `.claude`, and this repository keeps agent checkouts under `.claude/worktrees/`. **Adding `.claude` to that set would have been the wrong fix**: 68 files under `.claude/` are tracked here, 4 of them `.sh` files this guard exists to scan, and pruning the name would have blinded it to its own subjects while looking like a fix. Git's index cannot contain another checkout's files at all, so enumerating through it needs no name list to keep current. All 4 are still scanned. **How this was found, which is the part worth keeping.** `repo_root` was missing from `_ROOT_NAMES` in `repo_root_walks_use_git_15955_test.py` — and it is the name #15925 made canonical, so that detector's blind spot GREW as the migration landed: every guard moving to `repo_root()` moved toward a spelling it could not see. Keying on how a root is NAMED is the defect #15925 exists to remove, committed by the guard against it. Adding the name surfaced exactly two sites, both real, no false-positive explosion: tools/lint/check_git_toplevel_env_scrubbed.py:505 repo_root.rglob('*.sh') scripts/check_ansible_file_references_test.py:308 repo_root.iterdir() The second is single-level and benign — it collects top-level names — but it still enumerated other checkouts as entries, so it now prunes both nested roots. Two fixtures for the widening, positive and contrast: `repo_root.rglob(...)` and `repo_root.iterdir()` are reported, and `for root, dirs, files in os.walk(SUBDIR)` is not — without that, widening the name set is satisfied by flagging every `os.walk` body in the tree, since `root` is that loop's conventional variable. 116 passed across the affected suites; the guard now exits 0. Refs #15926, #15925, #15955, #15176 * fix(guards): land the shell-scan fix at the 600-line ceiling, not above it (#15926) The `rglob`->`tracked_paths` fix took `check_git_toplevel_env_scrubbed.py` to 612 against its 600 ceiling. Twelve of those lines were mine and eleven were comment: the measurement table and the reasoning about why adding `.claude` to the prune set would have been the wrong fix. That reasoning is worth keeping — it is now in the PR body and on #15926, where a reader looking for *why* will actually find it, rather than in a module where it costs a guarded budget. The ratchet is the mechanism that forces that judgement, which is the argument for having it. Not raised, deliberately. `RATCHET_BASELINES.md` merged an hour ago (#15959) and uses this ceiling as its worked example of a boundary that is declared, justified and guarded. Raising it to land a fix would have made that page's only passing example a failing one on the day it landed. Trimmed to exactly 600: - comment 11 lines -> 1 - `import pathlib` dropped; `rel.split("/")` needs no import, and git returns a POSIX relative path so the split is exact - `parts` inlined into the condition it feeds 76 passed across the affected suites, ratchet green, guard exits 0. Refs #15926, #15959, #14236 * fix(guards): only a confirmed non-checkout falls back to the walk (#15962 review) `_inside_work_tree` returned `False` for **every** non-zero `git rev-parse` exit, so an operational failure — git missing, a permissions error, a corrupt index — silently turned a real checkout into an `os.walk` of the repository root. That is the nested-checkout defect this change exists to remove, reached through its own remedy. Only git's own "not a git repository" now falls back. Any other failure raises, because a guard that cannot tell where it is has not established that walking is safe. Two tests, positive and contrast: a genuinely non-repository directory still falls back, and a simulated `fatal: index file corrupt` raises rather than walking. Mutation: restoring `return result.returncode == 0 and ...` fails `test_an_operational_git_failure_raises_instead_of_walking`. 23 passed; 430 lines, well under the 600 ceiling. Refs #15962, #15955 * chore(ci): re-trigger workflows for #15962 The push of e2b584a at 18:25 produced no workflow runs — CodeQL and semgrep reported, none of the ten required contexts did, and nothing was queued repo-wide an hour later. ci.yml has no `pull_request.paths` filter (removed by #14353, deliberately), the PR is not a draft, and the branch head matches the PR head, so the trigger conditions were met and the runs were simply never created. Empty commit to re-trigger. A squash merge discards it. Worth noting the failure mode rather than only the fix: with zero required contexts reported, a status histogram reads `pending=0 fail=0` and calls this PR green. That is #15995. * fix(guards): an empty enumeration must let the checker refuse audibly (#15962) `scan_helpers_vacuity_test` requires that a checker falling below its floor **says so on stderr**, not merely exits non-zero. My `rglob`->`tracked_paths` conversion broke that: `tracked_paths` raises on empty, so under the vacuity harness the checker died before reaching `enforce_reach`, which is the thing contracted to print the refusal. Exit code satisfied, contract broken. **Same boundary as `pytest_testpaths_cover_every_test_dir_15183_test.py`, from the other side.** There a caller asks "does this pattern match anything?", where empty is the finding. Here a caller has its OWN floor and is contracted to report empty in its own words. Both are callers for whom `tracked_paths`'s raise is the wrong answer, and neither wants the helper to stop raising. So the helper now distinguishes the two conditions it was conflating: `EmptyEnumeration(RuntimeError)` for "git succeeded and listed nothing", plain `RuntimeError` for "git failed". A subclass, so every existing `except RuntimeError` keeps working, and a caller with its own floor can tell them apart. That is the fix rather than an `allow_empty=` flag — an optional parameter that switches off a guard is off by default at every site that forgets it, which is #15930 and #15931. `iter_shell_files` absorbs **only** `EmptyEnumeration`. A git failure still propagates: that is an error, not a population of zero. Mutations, naming the test each kills: | mutation | test that failed | |---|---| | let the raise through again | `test_a_full_repo_sweep_below_the_floor_refuses[check_git_toplevel_env_scrubbed.py]` | | catch `RuntimeError` instead, swallowing git failures | `test_a_git_failure_still_propagates` | The second mutation **survived my first attempt** — nothing asserted that a git failure still propagates, which is the distinction the whole fix rests on. Two tests now pin both halves. 137 passed across the vacuity guard, the checker's suite, `_scan_helpers`, the census and the ratchet. Checker is 585 lines, under its 600 default. Refs #15962, #15926, #15826 --------- Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
1 participant
Closes #15897
Thinking Path
A ratchet freezes a baseline its own detector produced. At that moment the
baseline cannot distinguish "the tree contains N instances" from "the detector
can see N instances", and nothing in the pattern ever forces the difference to
surface. Whatever the detector is blind to becomes permanently exempt without
appearing in the list whose entire purpose is to record exemptions.
Five baselines were re-derived by implementations sharing neither enumeration nor
matching with their detectors (ACs 1–3, recorded on the issue). Four had a
boundary a reader cannot see. The one that passes is the one that declares and
guards it. This PR is ACs 4 and 5: writing that convention where ratchet
authors will meet it, with both a failure and a passing worked example.
The amendment to AC 4 matters and is carried in the doc's rules 1 and 2: the
criterion is not exact congruence. Every guard is scoped and a narrow scope is
not a defect — an undeclared scope is.
check_python_file_size.pyexcludes 47over-limit files and is the one clean instance precisely because it declares the
exclusion, justifies it, and pins it with a test that fails when it drifts.
What Changed
docs/developer/RATCHET_BASELINES.md(new, 184 lines) — six rules, thetwo-directions table, both worked examples, an evidence table across all five
baselines, and a checklist for new ratchets.
CLAUDE.md— one trigger-table row, per that file's own lean-instructionsrule.
Not folded into
CANONICAL_RULES.md: that file cataloguescanonical_check*.pyrules against a fixed per-rule schema, and this is a convention, not a rule with
a
RULE_ID.Verification
Every number was re-derived against
origin/Dev_new_guiat commit time ratherthan inherited from the drafting session, because a stale figure would make this
document an instance of its own subject.
astparse of both mirrorsno-commit-trailers.yml:79-95Two re-derivation failures happened while verifying this document and both are
now rules in it:
two variants; only the AST parse gave the true 497. Rule 4 and rule 6.
coauthor_re='^[[:space:]]*Co-authored-by:'as case-sensitive gave2,426 against the true 7,087. The
-isits on thegrepseventy linesbelow the assignment (
:165), and the dominant spelling in history isCo-Authored-By:(7,373 against 5,033), so dropping the flag silently discardsthe majority case. Rule 5 is extended to say the predicate is the pattern and
its invocation — the same wrong number was reached twice, by two readers,
from the same true regex.
Model Used
Claude Opus 5 (1M context). Analysis and doc drafted by a peer session
(
autobot-ai-b9) across five re-derivations; verification, the rule-5 extensionand the commit by this session.
Summary by CodeRabbit
Single-issue rationale: the deliverable is #15897's own acceptance criteria 4 and 5 — a convention documenting the five re-derivations already recorded on that issue. It has no code surface to share a CI suite with, and batching it with an implementation issue would put prose and behaviour in one review pass.