Overview

Update two $$SEARCH_META validation functions in search_helper.cpp to recognize $_documentResultsAndMetadata as a stage that sets $$SEARCH_META.

Background

Two functions gate $$SEARCH_META access but are unaware of the new container stage, causing false errors for extension-backed $search pipelines:

• assertSearchMetaAccessValidHelper throws error 6347902 ("can't access $$SEARCH_META without a $search stage") if no recognized setter appears earlier in the pipeline. It currently recognizes $_internalSearchMongotRemote, $search, $setVariableFromSubPipeline, and $_extensionSearch, but not $_documentResultsAndMetadata.
  • Side-question: Should $_extensionSearch be included here, or is $_documentResultsAndMetadata sufficient?
• shouldPreValidateMetaDependencies gates a pre-validation path. By the time it runs, buildFinalPipeline has reparsed the desugared LPP, meaning the original $_extensionStage is gone. It must recognize $_documentResultsAndMetadata directly.

Scope of Work

• Add $_documentResultsAndMetadata (conditioned on _metadata being present) to the recognized-setter list in assertSearchMetaAccessValidHelper
• Add $_documentResultsAndMetadata to the recognized-setter check in shouldPreValidateMetaDependencies

Acceptance Criteria

• Pipeline with $_documentResultsAndMetadata followed by $$SEARCH_META reference does not trigger error 6347902
• shouldPreValidateMetaDependencies correctly identifies extension-backed search pipelines
• Existing scoping error tests (6347901, 6347902) still pass