Add MongoDB parity tests for $in/$nin regex members and empty $elemMatch#10
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Every expectation encodes the behavior of a real mongod (verified against
MongoDB 7.x via mongodb-memory-server). Six tests currently fail and
document known divergences:
- a regex list member of $in must pattern-match string values (and string
elements of array fields); mingo compares it literally instead
- $nin must be the exact negation of $in
- {$elemMatch: {}} must match arrays containing at least one document
(object) element
The regression-guard section ($eq regex literal comparison, shorthand
regex, per-element array matching, type bracketing, missing-field
semantics) already agrees with MongoDB and must keep passing after a fix.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016iwZaQr7eue16AxGWLcA7E
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Adds
test/operators/query/mongodb-parity.test.ts: 18 test cases where every expectation encodes the behavior of a real mongod (verified against MongoDB 7.x via mongodb-memory-server, run side by side with mingo).Six tests fail by design on current
main(7.2.2) — they document divergences from MongoDB, discovered by differential fuzzing while building nosql-query-optimizer:$inmust pattern-match strings (MongoDB$indocs). mingo compares them literally instead:{f: {$in: [/^ab/]}}on{f: 'abc'}→ mongodtrue, mingofalse[/^a/, 5]) and string elements of array fields$ninis the exact negation of$in, so it must exclude pattern-matching strings:{f: {$nin: [/^ab/]}}on{f: 'abc'}→ mongodfalse, mingotrue{$elemMatch: {}}matches arrays containing at least one document (object) element:{f: {$elemMatch: {}}}on{f: [{x: 1}]}→ mongodtrue, mingofalseThe remaining 12 tests are regression guards for behavior that already agrees with MongoDB and must keep passing after any fix:
$eqwith a regex operand stays a literal comparison, shorthand regex criteria keep pattern-matching, per-element array matching, type bracketing, and missing-field semantics for$ne/$eq: null.Suggested fix direction (not included here): extend the shared
$in/$ninmembership helper so a RegExp list member also tests string values (and string elements of arrays) as a pattern, keeping the existing literal-equality path; make the empty-$elemMatchcase match arrays containing a plain-object element.🤖 Generated with Claude Code
https://claude.ai/code/session_016iwZaQr7eue16AxGWLcA7E
Generated by Claude Code