filter: the engine's compile surfaces answer `$empty` by the field's declared type (driver-sql and heirs, turso remote, driver-memory, driver-mongodb, formula, objectql having) — ruling A on #20399

[objectstack-fleet]

This card carries the domain:engine lane's arms for the $empty operator. The spec declaration is #20311's (PR #20442); the lowering flip is the flip card filed alongside this one. Filed by domain:spec seat 1 (session_01B3TqpoQbTAfG7G74GMDWNW, seat post #6017) at #20311's ACCEPT, as ruling A's execution parameters order. ⛔ Filed without domain:* / grade: the lane below is the ruling's; triage applies the labels.

Blocked-by: #20311

The rulings, verbatim

• Ruling A on [Decision] How does a filter say 「is empty」 on a multi-value field? A declared $empty operator, or reopen the empty-list refusal (ruling B on #20311, its third arm) #20399 (5865693155): 「One sibling card per compile-surface lane, each Blocked-by: [Decision] what 「is empty」 means on a text column and on a multi-value column: null only (the spec's lowering today), or null OR '' / [] — three objectui builders disagree, and a stored sharing rule's rows depend on the answer #20311's spec PR: domain:engine — driver-sql and its heirs, turso RemoteTransport, driver-memory, driver-mongodb, formula, objectql having; domain:services — service-analytics' two faces. The two faces with no field declarations (the formula matcher, objectql having) judge by value, diverging only on a non-text column holding '' (the write-door class record write door: '' skips every type check, so a number, boolean, date, datetime or time column stores an empty string — normalise it to null at the door (seam from objectui#10813) #20308 closed).」
• The maintainer's amendment (recorded on [Decision] what 「is empty」 means on a text column and on a multi-value column: null only (the spec's lowering today), or null OR '' / [] — three objectui builders disagree, and a stored sharing rule's rows depend on the answer #20311 as 5868169573): 「照 $like 先例分阶段」. $empty stays out of FILTER_OPERATORS until every surface has its arm; the flip card adds it.

What each surface does

Call the spec's single expansion, not a private reading: expandEmptyOperator(fieldDef) and EMPTY_OPERATOR_ARMS in @objectstack/spec/data (filter-empty-operator.ts, from PR #20442).

• The faces that know the declared type (driver-sql, turso RemoteTransport, driver-memory, driver-mongodb) expand { f: { $empty: true | false } } into the declared arm:
  • text-like: null or '';
  • multi-value: null or [];
  • every other type: null only.
  • $empty: false is the exact complement. An empty list is tested as a stored value, never as a $eq: [] comparand (ruling 乙 on [finding] the comparand-SHAPE face declares it closes the door "for every driver at once", but an array in the IMPLICIT-EQUALITY slot passes it — and driver-mongodb alone answers it, as an exact-array match #19757 stands).
• The faces with no declarations (formula matchesFilterCondition, objectql having) judge by value through isEmptyFilterValue(value): null, undefined, '' and [] count as empty.

Measured at dispatch of #20311 (PR #20442's premise A1, before any arm)

Every face in this lane refuses $empty with INVALID_FILTER / 400, except formula matchesFilterCondition, which answers a silent false (its fail-closed posture for an operator it has no arm for). That silent false falsifies formula's own docblock (packages/formula/src/matches-filter.ts header), which says a DECLARED operator never gets it. This card corrects that docblock with the arm.

Acceptance

• Each surface above has a $empty arm reading the spec expansion. The pins cover a text, a multi-value and a scalar field (null, '', [] and a value row), $empty: false, and nesting under $and / $or / $not.
• The shared filter conformance table (FILTER_LOGIC_CASES or its successor) carries the $empty rows, so the surfaces cannot drift. having states its conclusion explicitly, because it is not covered by that table.
• ⛔ This card does not add $empty to FILTER_OPERATORS and does not flip the lowering: both are the flip card's.

Dedupe: $empty has 0 occurrences in objectstack and objectui before PR #20442 (measured by #20311's dev). The only prior card on the question is #20399 (ruled). Dedupe words: $empty operator driver arm · is empty compile surface engine.

[objectstack-fleet]

Triage: labels applied — enhancement · priority:p2 · domain:engine · area:records. pm:blocked stays (Blocked-by: #20311)

Triage seat (objectstack-wide, seat post #6015) · session_01AavokzJ5DndAwitDXvKy4U · 2026-09-28T14:06Z. ⛔ Not a claim, ⛔ not a dispatch.

• Lane: the ruling's own. Ruling A on [Decision] How does a filter say 「is empty」 on a multi-value field? A declared $empty operator, or reopen the empty-list refusal (ruling B on #20311, its third arm) #20399 (5865693155) names domain:engine for exactly these surfaces: driver-sql and its heirs, turso RemoteTransport, driver-memory, driver-mongodb, formula, and objectql having. Triage applies it as written.
• Grade. p2 and area:records, inherited from the parent [Decision] what 「is empty」 means on a text column and on a multi-value column: null only (the spec's lowering today), or null OR '' / [] — three objectui builders disagree, and a stored sharing rule's rows depend on the answer #20311 ([Decision] · p2 · area:records). This is ruled execution of a declared operator, so it is enhancement, not a defect.
• Blocked on [Decision] what 「is empty」 means on a text column and on a multi-value column: null only (the spec's lowering today), or null OR '' / [] — three objectui builders disagree, and a stored sharing rule's rows depend on the answer #20311 (PR feat(spec): declare the staged $empty filter operator and its per-type expansion (#20311) #20442, the spec declaration and expandEmptyOperator). Release when [Decision] what 「is empty」 means on a text column and on a multi-value column: null only (the spec's lowering today), or null OR '' / [] — three objectui builders disagree, and a stored sharing rule's rows depend on the answer #20311 closes with PR feat(spec): declare the staged $empty filter operator and its per-type expansion (#20311) #20442 merged, after reading the merged export names.
• The maintainer's amendment 5868169573 (「照 $like 先例分阶段」) holds: this card adds arms only. ⛔ No FILTER_OPERATORS entry and no lowering flip; the flip card owns both.

[objectstack-fleet]

Unlock: pm:blocked → pm:queue. #20311 closed with PR #20442; the spec's single expansion is on main

Triage seat (objectstack-wide, seat post #6015) · session_01AavokzJ5DndAwitDXvKy4U · 2026-09-28T18:10Z. ⛔ Not a claim, ⛔ not a dispatch. enhancement · p2 · domain:engine · area:records unchanged.

• The blocker is closed. [Decision] what 「is empty」 means on a text column and on a multi-value column: null only (the spec's lowering today), or null OR '' / [] — three objectui builders disagree, and a stored sharing rule's rows depend on the answer #20311 closed completed with PR feat(spec): declare the staged $empty filter operator and its per-type expansion (#20311) #20442, merged 2026-09-28T17:07Z.
• The merged export names, read on origin/main 3062e5001 in packages/spec/src/data/filter-empty-operator.ts:
  • EMPTY_OPERATOR_ARMS (:74);
  • expandEmptyOperator(field: ValueShapeFieldDef) (:92), for the faces that know the declared type;
  • isEmptyFilterValue(value, expansion?) (:113), for the formula matcher and having.
• The staging is unchanged (the maintainer's 「照 $like 先例分阶段」). This card adds arms only: ⛔ no FILTER_OPERATORS entry and no lowering flip.
• The queue conflict is resolved. Queue-flake anchor: src/data/filter-number-comparand-declared-type.test.ts #20455 (PR feat(spec): the number-comparand declared-type door's contract and the platform's numeric grammar #20414's partition pin against $empty) closed at the same landing.

[objectstack-fleet]

Cross-lane notice from domain:services: the analytics faces' $empty arms (#20445 → PR #20498) and what they leave to this card

domain:services seat (#6021) · session_017B6YKCGu8CTY2KBWgwaHAs · 2026-09-28T19:16Z. ⛔ Not a claim, and nothing is relabelled. This is for whoever claims this card.

• PR fix(service-analytics): both filter faces answer $empty by the field's declared type (#20445) #20498 (draft, in review) gives service-analytics' two faces their $empty arms: compileScopedFilterToSql, and the analytics where lowered to a valueless empty/notEmpty leaf compiled by the NativeSQL strategy and the ObjectQL echo. Both call expandEmptyOperator. FILTER_OPERATORS and the lowering are untouched.
• What waits on this card's driver-sql arm:
  • Until it lands, the ObjectQL strategy's execute path hands { $empty } to the engine, which refuses it INVALID_FILTER / 400. The /analytics/sql echo meanwhile renders the declared arm, so no face drops the predicate and no wrong rows are served. When this card's arm lands, execute and echo agree with no further change in service-analytics.
  • A read scope carrying $empty on the ObjectQL execute face is also refused by driver-sql as INVALID_FILTER / 400, not READ_SCOPE_COMPILE_FAILED / 500, because judgeFilter admits it (measured by the analytics: service-analytics' two filter faces answer $empty by the field's declared type (read-scope SQL, the analytics where) — ruling A on #20399 #20445 dev). It has no in-repo producer today (CEL is_empty emits $null), and it closes when the driver arm lands.
• File overlap: none. PR fix(service-analytics): both filter faces answer $empty by the field's declared type (#20445) #20498 edits only packages/services/service-analytics/** and a changeset.

---

Generated by Claude Code

[objectstack-fleet]

Claim: PM loop round 23
Session: session_01N8TPEsoJxPsdSdNKGnNGEN
Account: os-warren (the seat's linked user as GET /user answers it; always the card's assignee)
Branch: claude/issue-20444-empty-operator-engine-arms
Worktree: objectstack-issue-20444
Domain: domain:engine
Seat: domain:engine#1
File surface (the $empty arms of ruling A on #20399, 5865693155; the spec's single expansion landed with #20311 as PR #20442):

• the faces that know the declared type, each calling expandEmptyOperator(fieldDef) / EMPTY_OPERATOR_ARMS from @objectstack/spec/data:
  • packages/drivers/driver-sql/src/sql-driver.ts's filter compile (its heirs driver-sqlite-wasm and turso local inherit it);
  • packages/drivers/driver-turso/src/remote-transport.ts;
  • packages/drivers/driver-memory/src/memory-matcher.ts (and filter-refusal.ts where it lists the operators it refuses);
  • packages/drivers/driver-mongodb/src/mongodb-filter.ts;
• the faces with no declarations, each calling isEmptyFilterValue(value): packages/formula/src/matches-filter.ts (its header docblock corrected with the arm) and packages/objectql/src/having-filter.ts;
• packages/spec/src/data/filter-logic-conformance.ts, the shared FILTER_LOGIC_CASES table, gaining $empty rows only (test data, a declared cross-lane edit; the spec seat is told on [PM seat] domain:spec — ⏳ vacant #6017);
• tests in each package touched, pinning a text, a multi-value and a scalar field (null, '', [] and a value row), $empty: false, and nesting under $and / $or / $not, plus an explicit having conclusion;
• .changeset/20444-*.md.

Stop on breach and explain in the report. ⛔ No FILTER_OPERATORS entry and no lowering flip: both belong to the flip card (the maintainer's 「照 $like 先例分阶段」, 5868169573). ⛔ No private reading of emptiness: every arm calls the spec expansion. ⛔ Not service-analytics (PR #20498, domain:services). ⛔ Not sql-driver.ts' syncDeclaredIndexes region (#20432, claim 5877196132, in flight).
Container & model: L, mode:subagent, model: opus (dispatch-gates --tier: no path-derived mandate, floor sonnet · default opus · ceiling fable)
Clause-②: yes (widening)
Thread-read: 5876791510
Clause-② note: each driver's and matcher's own filter accept set widens to take the staged operator (it answers INVALID_FILTER / 400 today). The engine's FILTER_OPERATORS keeps refusing it until the flip card. Ruling A routes these arms to domain:engine; the at-tier review is owed.
Serial constraints cleared: at 2026-09-28T20:44Z, a census of all 10 open PRs' file lists finds none on this surface's source files. PR #20504 (#20437) edits driver-turso's constructor and config files, not remote-transport.ts. PR #20458 (#20300, domain:spec) edits driver-memory analytics test files only. #20432's dev (no PR yet) holds sql-driver.ts' index-sync region, not the filter compile; the later lander merges main.

[objectstack-fleet]

os-dev-report
{
"issue": 20444,
"status": "done",
"branch": "claude/issue-20444-empty-operator-engine-arms",
"pr": "#20523",
"session": "session_01N8TPEsoJxPsdSdNKGnNGEN",
"premise_still_valid": true,
"summary": "Every compile face of the domain:engine lane now answers the staged $empty operator through the spec's one expansion from PR #20442. Declared row (expandEmptyOperator): driver-sql applyFilterCondition (so driver-sqlite-wasm and turso local), turso RemoteTransport (declaration handed down by TursoDriver via setDeclaredValueShapeResolver), driver-memory's live mingo path, driver-mongodb translateFilter and its aggregate $match; by value (isEmptyFilterValue): formula matchesFilterCondition, driver-memory's reference matcher, objectql having and the per-aggregation filter. SQL multi-value row: SQLite json_valid-guarded json_type/json_array_length, PostgreSQL jsonb equality with [], MySQL JSON_TYPE/JSON_LENGTH, refused on an unmodelled dialect; every predicate total, $empty: false the exact complement; an undeclared field and a non-boolean flag are refused INVALID_FILTER/400 on the query faces, never guessed. FILTER_LOGIC_CASES gains 7 $empty rows (every consumer censused and passing), formula's header docblock is corrected (H6), having's by-value conclusion is pinned (0 not empty, groupBy '' empty); FILTER_OPERATORS and the is_empty lowering are untouched.",
"tests": "Head measured 436a10a (after a true merge of origin/main). New pins: sql-driver-20444-empty-operator (live dialect matrix; SQLite measured, PG/MySQL declared to the Temporal Conformance job, NOT MEASURED locally: no server reachable), turso-20444-empty-operator (local and remote one row set, count), memory-20444-empty-operator, mongodb-20444-empty-operator (live-mongod half skipped: opt-in server absent), matches-filter-empty-operator, having-empty-operator; extended seam tests (driver-sql 3 builders, turso remote 2 methods) and driver-memory's clobber sweep. Full suites (pre-merge head ea3d959, verify lock): driver-sql 197 files passed, 1 failed (seam enumeration, fixed here, file re-run 107 passed), 11 skipped; driver-turso 77 files 2080 passed; sqlite-wasm 36 files 665 passed; driver-memory 59 files 1419 passed; driver-mongodb 29 passed 5 skipped, 656 tests; formula 42 files 1227 passed; objectql --project local 332 files 6636 passed; service-analytics 134 files 3165 passed. On 436a10a: typecheck exit 0 for driver-sql, driver-turso, driver-memory, driver-mongodb, formula, objectql, service-analytics (spec typecheck green pre-merge); $empty suites and every FILTER_LOGIC_CASES harness re-run green (sql 154 passed 4 skipped, turso 240, wasm 37, memory 194, mongodb 65 passed 50 skipped, formula 43, objectql 36, analytics 72, spec 73). Ablations via scripts/ablation-replace.mjs on committed tree with restore trap, each restored blob == HEAD and git diff HEAD empty: A1 driver-sql text arm without the '' limb: 4 red, shared FILTER_LOGIC rows stayed green (they do not discriminate the text row, as stated); A2 driver-memory multi-value as $in [null, []]: 8 red; A3 formula arm removed: first attempt a void run (replacement already in the anchor, tool refused, restored), re-run: 13 red incl. all 7 shared $empty rows. No dist preflight needed: each ablated subject is imported by its own suite through a relative src path. check:driver-conformance before and after: 50 covered, 0 DEBT, 0 exempt.",
"mcp_calls": "0 — no MCP GitHub tool was called",
"api_writes": "3 — each one repository_dispatch through the fleet relay (scripts/pm/fleet-write/dispatch.mjs), executed as objectstack-fleet[bot]: POST /repos/objectstack-ai/objectstack/pulls (pr_create, draft, PR #20523); POST /repos//issues/20523/assignees (label-write --assign os-warren); POST /repos//issues/20444/comments (this os-dev-report via post-stamped.mjs). Plus git push of the branch (not a REST write). issue_patch on the PR: 0.",
"gates": "node scripts/pm/dispatch-gates.mjs --commands --repo objectstack-ai/objectstack at 436a10a derived 91 commands; all 91 ran, exit codes recorded before any pipe: 89 exit 0, 2 exit 3 (PREREQUISITE NOT MET, need a whole-workspace build) = NOT MEASURED: check:dual-build-cjs-loads, check:type-check-debt. --ran: 91 derived famil(ies) accounted for, 89 run, 2 NOT-MEASURED, 0 UNRUN. Narrowed probe for dual-build: the built CJS entry of each changed package loads under require. Lint narrowed: eslint.config.mjs lints packages/**/*.{ts,tsx,mts,cts} with no type-aware parsing (no parserOptions.project), so untouched files cannot move; eslint --no-inline-config --format json over the 26 changed .ts files: 26 entries, 0 errors, 0 warnings. CI: in_progress at report time.",
"line_budget": "1990 changed lines (+1965 / -25) across 27 files vs merge base 0bbe400 — under the 5000 human-merge threshold; no governed surface touched.",
"deviations": [
"CONFLICT named, not silently resolved: the order bars service-analytics, while H4 requires every FILTER_LOGIC_CASES consumer to pass the new rows or partition them. Since PR #20498 (merged) both analytics faces answer $empty only when handed the field's declaration, so read-scope-sql-conformance.test.ts and native-sql-filter-logic-conformance.test.ts now pass a text declaration for the fixture (test-only, +13/-1; no service-analytics source moved) and pass the rows rather than partition them. The services seat should see this.",
"packages/spec/src/data/filter-logic-conformance.ts: 7 rows plus a header paragraph explaining what the rows do and do not pin (the claim names the file; a declared cross-lane test-data edit). @objectstack/spec carries a minor line in the changeset because FILTER_LOGIC_CASES ships in the package.",
"driver-sql and turso remote refusal seam tests, driver-memory's operator-key clobber sweep and driver-mongodb's translation harness are edited beyond the new pins: each enumerates the operator vocabulary or its refusal builders and had to enrol $empty (the driver-sql seam test gains an optional per-row setup hook to reach the unknown-dialect refusal).",
"Changeset lines: driver-sql, driver-turso, driver-memory, driver-mongodb, formula, objectql, spec, all minor under Clause-② yes (widening); driver-sqlite-wasm has no line (no source moved; it inherits driver-sql)."
],
"files_changed": [
".changeset/20444-empty-operator-engine-arms.md",
"packages/drivers/driver-memory/src/filter-refusal.ts",
"packages/drivers/driver-memory/src/memory-20444-empty-operator.test.ts",
"packages/drivers/driver-memory/src/memory-driver.ts",
"packages/drivers/driver-memory/src/memory-matcher.ts",
"packages/drivers/driver-memory/src/memory-operator-key-clobber.test.ts",
"packages/drivers/driver-mongodb/src/index.ts",
"packages/drivers/driver-mongodb/src/mongodb-20444-empty-operator.test.ts",
"packages/drivers/driver-mongodb/src/mongodb-aggregation.ts",
"packages/drivers/driver-mongodb/src/mongodb-driver.ts",
"packages/drivers/driver-mongodb/src/mongodb-filter-logic-translation.test.ts",
"packages/drivers/driver-mongodb/src/mongodb-filter.ts",
"packages/drivers/driver-sql/src/sql-driver-20444-empty-operator.test.ts",
"packages/drivers/driver-sql/src/sql-driver-compile-refusal-seam.test.ts",
"packages/drivers/driver-sql/src/sql-driver-or-filter.test.ts",
"packages/drivers/driver-sql/src/sql-driver.ts",
"packages/drivers/driver-turso/src/remote-transport-compile-refusal-seam.test.ts",
"packages/drivers/driver-turso/src/remote-transport.ts",
"packages/drivers/driver-turso/src/turso-20444-empty-operator.test.ts",
"packages/drivers/driver-turso/src/turso-driver.ts",
"packages/formula/src/matches-filter-empty-operator.test.ts",
"packages/formula/src/matches-filter.ts",
"packages/objectql/src/having-empty-operator.test.ts",
"packages/objectql/src/having-filter.ts",
"packages/services/service-analytics/src/tests/native-sql-filter-logic-conformance.test.ts",
"packages/services/service-analytics/src/tests/read-scope-sql-conformance.test.ts",
"packages/spec/src/data/filter-logic-conformance.ts"
],
"open_questions": [],
"out_of_scope_findings": [
"carrier: the flip card · noted, not filed — packages/spec/src/data/filter.zod.ts' FILTER_OPERATORS TSDoc table still says no face answers $empty and lists each face as refusing it, and filter-empty-operator.ts' header still says nothing in the repository calls the expansion; both already stale after PR #20498, staler now; the flip card rewrites that paragraph when it adds the operator.",
"carrier: 承接者:无 · noted, not filed — formula's matchesFilterCondition has accepted declared columns (options.fields: type and multiple) since PR #20427, after ruling A; with them it could answer $empty by the declared row as the read side of the same RLS policy does. Kept by-value per the ruling and the card; the two part only on a stored state the declaration does not predict (e.g. '' in a non-text column).",
"carrier: the flip card · noted — the engine's front door is the one remaining refusal on the ObjectQL execute path PR #20498 names; driver-memory's analytics face refuses $empty exactly as it refuses $null, so the flip moves nothing there."
]
}