Null Start Date on Planner Task

[nhalvorson]

I'm trying to pass a null value for the start date on 'Create a task'. The start date is listed in the step (and documentation) as an optional field, yet it won't run the flow without it. This is the failure feedback that I'm receiving:

The request is invalid: Cannot convert the literal '' to the expected type 'Edm.DateTimeOffset'. 

{
  "error": {
    "code": "",
    "message": "The request is invalid:\r\nCannot convert the literal '' to the expected type 'Edm.DateTimeOffset'.",
    "innerError": {
      "request-id": "8c883428-a179-485c-961f-e5b538d44a20",
      "date": "2018-03-12T14:29:32"
    }
  }
}

My intent is to allow the task to be created with or without a start date, then updated through a separate flow if a start date is assigned or modified later. This is the expression that I'm using on the create flow 'Start Date Time' step: 

if(empty(triggerBody()?['Assigned_x0020_Start_x0020_Date']), null, triggerBody()?['Assigned_x0020_Start_x0020_Date'])

Any thoughts for getting the step to accept a task with no start date?

[v-yuazh-msft]

Hi @ nhalvorson,

Where is the task’s start date saved in?

Could you please share a screenshot of your flow's configuation?

I have made a test on my side, you couldn’t insert the null value in the “Start Date Time” field of the “Create a task” action of Planner connector.

For you situation, you could add a Condition to check if the “start date” is null,the expression in the Condition as below:

@empty(triggerBody()?['Assigned_x0020_Start_x0020_Date'])

if the “start date” is null, then the flow wouldn’t insert the “start date” in the “Start Date Time” field of the “Create a task” action, if the “start date” isn’t null, then the flow would insert the “start date” in the “Start Date Time” field of the “Create a task” action.

Regards,
Alice Zhang