Freeze audit: refresh stale ≤18-era / signed-decimal docstrings (issue #68)

[espg]

Refs #68 (sub-issue of #48, dovetails with #60). Phase-1 audit for the 1.x freeze: a full pass over mortie/*.py and src_rust/src/*.rs for ≤18-era order caps, signed-decimal assumptions, and stale docstrings, plus an enumeration of the public API surface.

Bottom line: the codebase has already been largely modernized by the packed-u64 work (#48/#58/#60/#120). The encoding-range docstrings that once said "1–18" are already gone; the residual stale wording was in the prefix-trie module. Mechanical fixes are folded in below; everything touching runtime behavior or the public surface is raised for review rather than changed (per the freeze's no-unilateral-API-change rule — downstream like zagg imports these names).

File:line refs below were re-verified against this branch's actual files after self-review (mortie/tools.py is 866 lines here); they are accurate for claude/68-freeze-audit.

Phases

• Phase 1 — audit sweep + fold in mechanical docstring fixes; raise design/public-surface questions.
• Phase 2 (pending @espg answers) — act on the public-surface verdicts and the clip2order order-cap decision below.

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(i) Mechanical fixes folded in (this commit)

Docstring-only, no behavior change:

• mortie/prefix_trie.py:232 and :311 — parameter docstring said "Morton indices (signed integers)." The input is cast to np.uint64 at prefix_trie.py:242; the words are packed uint64 (base cells 7‑11 set bit 63), not signed int64. Updated to "Morton indices (packed uint64 words; base cells 7‑11 set bit 63)." to match the language in tools.py.

(ii) Public API surface — verdicts (mortie/__init__.py __all__)

No visibility changed. Enumerated __all__ (__init__.py:72-119) plus the lazy += additions (:149-150). Most exports are clearly intended-frozen (geo2mort, mort2geo, mort2bbox, mort2polygon, infer_order_from_morton, validate_morton, mort2norm, norm2mort, order2res, unique2parent, mort2healpix, morton_buffer[_meters], the morton_coverage* / moc_* / common_ancestor / moc_min / split_base_cells MOC family, linestring_coverage, the from_*/to_* geometry codecs, generate_morton_children, clip2order, and the MortonIndex* / Arrow _ARROW_NAMES).

Questionable — flagged for an @espg keep/privatize/reshape decision (I did NOT change them):

1. res2display (tools.py:27) — a print()-only helper with no useful return value. Odd thing to freeze in a public API. Keep as-is, or return structured data / move to a docs example?
2. MortonChild (prefix_trie.py:40) — exposes an internal compacted-trie node class (its __init__ takes a raw shared char-array + mask). Freezing this locks the trie's internal representation into the public contract. Intended, or should the frozen surface be just the *_polygon functions that return lists of these?
3. heal_norm (tools.py:74) — undocstringed low-level (base, order, addr_nest) -> addr_norm helper. Intended public, or an internal used only by norm2mort/geo2uniq?
4. The UNIQ helpers geo2uniq (tools.py:121) / norm2uniq (tools.py:302) / uniq2geo (tools.py:331) and unique2parent (tools.py:56) — unique2parent is self-described as "such an ugly hack … will blow up with multi res" and raises NotImplementedError on mixed resolution. Freeze the UNIQ helpers as-is for 1.x, or mark them provisional?
5. split_children / split_children_geo (prefix_trie.py:226/252) — low-level trie builders exposed alongside the higher-level morton_polygon*. Borderline; likely intended but worth confirming they're part of the frozen contract.

(No dependency concern found: heal_norm/geo2uniq/uniq2geo use the internal Rust-backed mortie._healpix (hp), not healpy — numpy stays the only runtime dep.)

(iii) Stale order-cap / signed findings needing a design decision (NOT changed here)

1. clip2order(print_factor=True) is hard-anchored to order 18 — tools.py:643-644 (docstring) and tools.py:653 (return 18 - clip_order). The "levels dropped" count is computed against a fixed 18, a ≤18-era assumption; for order‑19…29 words the returned count is wrong (e.g. clipping an order‑29 word to order‑20 reports 18-20 = -2). This is a behavioral fix, so I did not touch it. Options: (a) use the word's actual decoded order instead of 18; (b) use MAX_ORDER; (c) deprecate print_factor for the freeze. May warrant its own issue — needs @espg go-ahead.

Confirmed clean (no change needed)

• Rust doc-comments already describe the current encoding correctly: morton.rs:57 (order range 0..=29), moc.rs:29,771 (MAX_DEPTH lifted 18→29 for morton_coverage/morton_coverage_moc cap order at 18 while geo2mort accepts up to 29 #60), decimal_morton.rs and morton_index.py:543-559 legacy to_legacy_i64 references (the legacy decimal genuinely tops out at order 18 due to int64 overflow — correct, intentional compat). No .rs files were edited.
• The prefix-trie cell_area digit-count→order contract is correct (prefix_trie.py:159-172): the characteristic is the decode-through-kernel decimal repr (prefix_trie.rs:1-14,66-100), which is the order‑0…29 generalization — one sign column + one base‑4 digit per order — so counting digits still yields the order. Not stale.
• No hidden behavioral order‑18 caps remain in the polygon/linestring/MOC paths — those were lifted under morton_coverage/morton_coverage_moc cap order at 18 while geo2mort accepts up to 29 #60 (see test_coverage.py:669,683). The only literal 18 comparisons in code are the intentional legacy to_legacy_i64 cap and the clip2order item in (iii).

How tested

• maturin/editable build green; mortie imports.
• flake8 mortie --select=E9,F63,F7,F82 — clean.
• pytest — 683 passed, 11 skipped, 1 failed. The single failure is the pre-existing test_spec_page.py::TestDecimalParseTieBreak::test_order29_string_parses_to_area_word (issue main is red: test_spec_page tie-break test predates #120's p-suffix rendering #123, main is already red on it), unrelated to this docstring change.
• No .rs changes, so cargo gates not exercised.

Questions for review

• The five public-surface items in (ii) — for each: keep frozen as-is, privatize, or reshape before 1.0? (I will not change any public name without your go-ahead.)
• The clip2order order‑18 anchor in (iii) — fix in this PR (phase 2), or split to its own issue?
• Should this close v1.0: full codebase review for the 1.x freeze #68, or stay open until the above decisions land? (Using Refs, not Closes, for now.)

🤖 Generated with Claude Code

[espg]

🤖 from Claude (review)

Fresh-context adversarial review of the 1.x-freeze audit. Verdict: looks good to advance — the diff is safe and the audit's claims hold up under spot-checking. No diff-scoped changes required.

Diff verification (non-behavioral, accurate)

• The only code change is 2 docstring param lines in mortie/prefix_trie.py (232, 311): "Morton indices (signed integers)." → "Morton indices (packed uint64 words; base cells 7-11 set bit 63).". git diff main... shows one commit, 2 insertions(+), 2 deletions(-), nothing else.
• The new wording is correct: split_children casts its input with np.ascontiguousarray(np.asarray(morton_array, dtype=np.uint64)) (prefix_trie.py:242), so the old "signed integers" was genuinely stale. morton_polygon_from_array routes through the same split_children.
• No public export removed / renamed / privatized, no signature change, no behavior change — this respects the freeze rule. Docstring-only, so the CLAUDE.md §4 "tests for behavioral change" gate does not apply.

Audit claims spot-checked — all confirmed

• tools.py:643-653 clip2order(print_factor=True) returns a hard-coded 18 - clip_order. This is a genuine latent behavioral quirk (assumes source order 18 regardless of the words' actual order), and the docstring already flags it as legacy back-compat. Correctly left unfixed and raised for espg rather than silently "corrected" — agreed, changing it is a behavior/API call.
• prefix_trie.py:159-172 cell_area digit-count contract reads as described.
• Rust is clean: decimal_morton::MAX_ORDER = 29, moc.rs MAX_DEPTH = MAX_ORDER (31), and the doc-comments at morton.rs:57, moc.rs:29, moc.rs:771 all state 0..=29 / 1..=29 and explicitly note the old 18 was the retired decimal-i64 ceiling, not a u64 limit. No stale order cap in src_rust/src/*.rs.

Adversarial sweep for anything missed — nothing found

• No remaining literal order-18 behavioral cap in mortie/*.py or the Rust sources; every order=18 is a default parameter value, and lib.rs validates against MAX_ORDER, not 18.
• No stale "signed integers" / "orders 0-18" docstring describing the current encoding wrongly. The remaining Morton indices docstrings (tools.py:719,766 "same order", coverage.py:280,308,549,608 "mixed order allowed") are accurate. All 0..=18 mentions I could find are correctly legacy-scoped (to_legacy_i64, from_legacy, decimal_repr_matches_legacy_*) and not in scope per the freeze audit.
• No signed-southern-hemisphere assumption remaining in the public path; the signed hits are legitimate (spherical signed-area geometry, the normed/parent note, unsigned-Z-order regression tests).

Standing note for espg (not a directive): the clip2order print_factor hard-coded 18 (tools.py:653) is the one live behavioral wart the audit surfaces. Confirm whether it should stay frozen as-is for 1.x back-compat or be reworked to a real per-word level count — that's a scope/API decision, correctly deferred to you rather than folded into this docstring PR.

No inline diff-line findings; the 2 changed lines are correct as written.

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Generated by Claude Code

[codspeed-hq]

Merging this PR will not alter performance

✅ 67 untouched benchmarks
⏩ 1 skipped benchmark¹

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_{Comparing claude/68-freeze-audit (66f0491) with main (4b57a1f)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩

[espg]

🤖 from Claude (review)

Adversarial review of the freeze-audit (issue #68 acceptance criterion is an accurate file:line findings list, so I checked the refs, not just the diff).

Diff itself — clean. Both docstring edits are accurate: input is cast to np.uint64 at prefix_trie.py:242, and the new wording ("packed uint64 words; base cells 7-11 set bit 63") matches the established language at tools.py:340. Docstring-only, no runtime behavior touched, no __all__ visibility changed. Good call leaving the clip2order order-18 anchor (return 18 - clip_order, real, at tools.py:806) as a raised behavioral finding rather than silently fixing it — that respects the no-unilateral-change scope.

One defect: several findings-list file:line refs in the PR body are wrong (the substance is correct, the coordinates are stale). Since the deliverable per #68 is the ref'd list, these should be corrected:

• Finding (iii) clip2order — cited tools.py:643-645 (docstring) and tools.py:653 (return 18 - clip_order). Actual: docstring at tools.py:795-798, return at tools.py:806. (Lines 643-653 are the unrelated antimeridian helper.)
• Section (ii) item 4 — norm2uniq cited tools.py:302, actual tools.py:388; uniq2geo cited tools.py:331, actual tools.py:417. (geo2uniq:121 and unique2parent:56 are correct.)

Everything else I spot-checked matched: res2display:27 (confirmed print-only, no return), heal_norm:74, MortonChild:40, split_children:226, split_children_geo:252, __all__ at __init__.py:72 / lazy += at 149-150, and morton.rs 0..=29 near :57. Findings are otherwise well-grounded and the clean/behavioral separation is sound.

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Generated by Claude Code