findOneAndUpdate() seems to not return result if no updates to apply

[vkarpov15]

Send the following commands to jsonapi and you'll see that findOneAndUpdate() returns no results, even though there's a document that matches.

{
  "deleteMany": {
    "filter": {}
  }
}

{
  "insertMany": {
    "documents": [
      {
        "username": "a"
      }
    ]
  }
}

{
  "findOneAndUpdate": {
    "filter": {},
    "update": {
      "$set": {
        "username": "a"
      }
    },
    "options": {
      "returnDocument": "before"
    },
    "sort": {
      "username": 1
    }
  }
}

Change the last command to the following and a document is returned.

{
  "findOneAndUpdate": {
    "filter": {},
    "update": {
      "$set": {
        "username": "aaa"
      }
    },
    "options": {
      "returnDocument": "before"
    },
    "sort": {
      "username": 1
    }
  }
}

[maheshrajamani]

@vkarpov15 If there is no update to the document, the api currently doesn't return document. Will make the change to return document in this scenario too.

[maheshrajamani]

@vkarpov15 I believe this behavior is required for findOneAndReplace() api too?

[vkarpov15]

@maheshrajamani yes, findOneAndReplace() as well. Although it looks like findOneAndReplace() isn't affected - the following series of commands seems to result in a document being returned from findOneAndReplace():

{
  "deleteMany": {
    "filter": {}
  }
}

{
  "insertMany": {
    "documents": [
      {
        "username": "a"
      }
    ]
  }
}

{
  "findOneAndReplace": {
    "filter": {},
    "replacement": {
      "$set": {
        "username": "a"
      }
    },
    "options": {
      "returnDocument": "before"
    },
    "sort": {
      "username": 1
    }
  }
}