description: db-aggregate-write-readPreference

schemaVersion: '1.4'

runOnRequirements:
  # 3.6+ non-standalone is needed to utilize $readPreference in OP_MSG.
  # Serverless does not support $listLocalSessions and $currentOp stages, and
  # mongos does not allow combining them with $out or $merge.
  - minServerVersion: "3.6"
    topologies: [ replicaset ]
    serverless: forbid

_yamlAnchors:
  readConcern: &readConcern
    level: &readConcernLevel "local"
  writeConcern: &writeConcern
    w: &writeConcernW 1

createEntities:
  - client:
      id: &client0 client0
      observeEvents:
        - commandStartedEvent
      # Used to test that read and write concerns are still inherited
      uriOptions:
        readConcernLevel: *readConcernLevel
        w: *writeConcernW
  - database:
      id: &database0 database0
      client: *client0
      databaseName: &database0Name db0
      databaseOptions:
        readPreference: &readPreference
          # secondaryPreferred is specified for compatibility with clusters that
          # may not have a secondary (e.g. each shard is only a primary).
          mode: secondaryPreferred
          # maxStalenessSeconds is specified to ensure that drivers forward the
          # read preference to mongos or a load balancer. That would not be the
          # case with only secondaryPreferred.
          maxStalenessSeconds: 600
  - collection:
      id: &collection0 collection0
      database: *database0
      collectionName: &collection0Name coll0

initialData:
  - collectionName: *collection0Name
    databaseName: *database0Name
    documents: []

tests:
  - description: "Database-level aggregate with $out includes read preference for 5.0+ server"
    runOnRequirements:
      - minServerVersion: "5.0"
        serverless: "forbid"
    operations:
      - object: *database0
        name: aggregate
        arguments:
          pipeline: &outPipeline
            - { $listLocalSessions: {} }
            - { $limit: 1 }
            - { $addFields: { _id: 1 } }
            - { $project: { _id: 1 } }
            - { $out: *collection0Name }
    expectEvents:
      - client: *client0
        events:
          - commandStartedEvent:
              command:
                aggregate: 1
                pipeline: *outPipeline
                $readPreference: *readPreference
                readConcern: *readConcern
                writeConcern: *writeConcern
    outcome: &outcome
      - collectionName: *collection0Name
        databaseName: *database0Name
        documents:
          - { _id: 1 }

  - description: "Database-level aggregate with $out omits read preference for pre-5.0 server"
    runOnRequirements:
      # MongoDB 4.2 introduced support for read concerns and write stages.
      # Pre-4.2 servers may allow a "local" read concern anyway, but some
      # drivers may avoid inheriting a client-level read concern for pre-4.2.
      - minServerVersion: "4.2"
        maxServerVersion: "4.4.99"
        serverless: "forbid"
    operations:
      - object: *database0
        name: aggregate
        arguments:
          pipeline: *outPipeline
    expectEvents:
      - client: *client0
        events:
          - commandStartedEvent:
              command:
                aggregate: 1
                pipeline: *outPipeline
                $readPreference: { $$exists: false }
                readConcern: *readConcern
                writeConcern: *writeConcern
    outcome: *outcome

  - description: "Database-level aggregate with $merge includes read preference for 5.0+ server"
    runOnRequirements:
      - minServerVersion: "5.0"
    operations:
      - object: *database0
        name: aggregate
        arguments:
          pipeline: &mergePipeline
            - { $listLocalSessions: {} }
            - { $limit: 1 }
            - { $addFields: { _id: 1 } }
            - { $project: { _id: 1 } }
            - { $merge: { into: *collection0Name } }
    expectEvents:
      - client: *client0
        events:
          - commandStartedEvent:
              command:
                aggregate: 1
                pipeline: *mergePipeline
                $readPreference: *readPreference
                readConcern: *readConcern
                writeConcern: *writeConcern
    outcome: *outcome

  - description: "Database-level aggregate with $merge omits read preference for pre-5.0 server"
    runOnRequirements:
      - minServerVersion: "4.2"
        maxServerVersion: "4.4.99"
    operations:
      - object: *database0
        name: aggregate
        arguments:
          pipeline: *mergePipeline
    expectEvents:
      - client: *client0
        events:
          - commandStartedEvent:
              command:
                aggregate: 1
                pipeline: *mergePipeline
                $readPreference: { $$exists: false }
                readConcern: *readConcern
                writeConcern: *writeConcern
    outcome: *outcome