feat(mongo): allow trailing comma in argument lists#127
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mongosh and JavaScript (since ES2017) accept a trailing comma at the end
of a function-call argument list. Production telemetry shows the shape
in the wild — e.g. `db.coll.find({…},).sort({…})` — pasted from editors
or generated by code formatters. The parser previously rejected the
trailing `,` with `expected ,, got ")"`, forcing the caller to fall back
to mongosh.
parseArguments now accepts a single trailing comma after a real argument
while still rejecting bare `(,)`, leading `(,a)`, and consecutive `(a,,)`.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
rebelice
approved these changes
May 9, 2026
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Summary
db.coll.find({…},).sort({…})— comes up in production telemetry from editors and code formatters; previously the parser rejected the trailing,withexpected ,, got ")".Behavior
db.coll.find({a: 1},)→ okdb.coll.find({}, {a: 1},)→ okdb.coll.find({a: 1},).sort({a: 1})→ ok (cursor chain unaffected)db.coll.find().limit(10,)→ ok (cursor-method args also tolerate it)db.coll.find(,)/db.coll.find(, {a: 1})/db.coll.find({a: 1},,)→ still errorTest plan
TestTrailingCommaInArgumentscovers all four success shapes including the exact wild case.TestArgumentListErrorsconfirms bare/leading/consecutive commas still fail.go test ./mongo/...passes (analysis, catalog, completion, parsertest).🤖 Generated with Claude Code