Expressions with $project

db.movies.aggregate([
    {
      $match: {
        cast: { $elemMatch: { $exists: true } },
        directors: { $elemMatch: { $exists: true } },
        writers: { $elemMatch: { $exists: true } }
      }
    },
    {
      $project: {
        _id: 0,
        cast: 1,
        directors: 1,
        writers: {
          $map: {
            input: "$writers",
            as: "writer",
            in: {
              $arrayElemAt: [
                {
                  $split: ["$$writer", " ("]
                },
                0
              ]
            }
          }
        }
      }
    },
    {
      $project: {
        labor_of_love: {
          $gt: [
            { $size: { $setIntersection: ["$cast", "$directors", "$writers"] } },
            0
          ]
        }
      }
    },
    {
      $match: { labor_of_love: true }
    },
    {
      $count: "labors of love"
    }
  ])