Summary
Add comprehensive test coverage for aggregation system variables. This includes feature tree entries, smoke tests, and detailed compatibility tests.
System Variables to Cover
Variable
Context
Priority
$$ROOTFull current document
High
$$CURRENTCurrent document (equivalent to field paths)
High
$$REMOVERemove field from output
High
$$NOWCurrent datetime
High
$$CLUSTER_TIMECurrent cluster time (replica set)
Medium
$$DESCEND$redact stageMedium
$$PRUNE$redact stageMedium
$$KEEP$redact stageMedium
$$USER_ROLESCurrent user roles
Low
Tasks
core,operator,expressions,variable,system-variablesexpressions/variable/system-variables/:
$$ROOT — in $project, $addFields, nested paths ($$ROOT.a.b), inside $cond$$CURRENT — equivalence with field paths, in various expression contexts$$REMOVE — in $project, $addFields, conditional removal ($cond + $$REMOVE), nested fields$$NOW — type verification, consistency within a pipeline, usage in date expressions$$DESCEND/$$PRUNE/$$KEEP — with $redact stage$$CLUSTER_TIME — type verification, availability
Test Location
documentdb_tests/compatibility/tests/core/operator/expressions/variable/system-variables/
Notes
$let variable scoping is already covered in PR Add $let and $literal tests #102 Per TEST_COVERAGE.md, system variables are shared expression engine behavior — test once with a representative operator, not per-operator
Summary
Add comprehensive test coverage for aggregation system variables. This includes feature tree entries, smoke tests, and detailed compatibility tests.
System Variables to Cover
$$ROOT$$CURRENT$$REMOVE$$NOW$$CLUSTER_TIME$$DESCEND$redactstage$$PRUNE$redactstage$$KEEP$redactstage$$USER_ROLESTasks
core,operator,expressions,variable,system-variablesexpressions/variable/system-variables/:$$ROOT— in$project,$addFields, nested paths ($$ROOT.a.b), inside$cond$$CURRENT— equivalence with field paths, in various expression contexts$$REMOVE— in$project,$addFields, conditional removal ($cond+$$REMOVE), nested fields$$NOW— type verification, consistency within a pipeline, usage in date expressions$$DESCEND/$$PRUNE/$$KEEP— with$redactstage$$CLUSTER_TIME— type verification, availabilityTest Location
Notes
$letvariable scoping is already covered in PR Add $let and $literal tests #102