Function returns a 400 Bad Request when called on a work item with more than 200 children

[sobjornstad]

Steps to reproduce

Aggregator CLI 0.9.2.

Attempt to access the .Children property of a work item that has more than 200 child items.

Here is the rule that is failing intermittently for us (when the work item posted happens to have more than 200 children...and before you ask, I'm not the one who decided to have work items with more than 200 children!).

.lang=C#

/*
*
* AutoClose update PBI states based on child items.
*
*/

var debug=false;
var areaPathFilter = "Federated Projects\\GregTest";

var appliesToWorkItemTypes = new[] {"Task", "Bug", "Milestone"};
var statesCausingParentClose = new[] {"Removed", "Done"};
var statesParentIsUnchangedIn = new[] {"Removed", "Done"};
var closedState = "Done";

if(debug && self.AreaPath != areaPathFilter)
{
    logger.WriteInfo($"This rule is in debug mode, and therefore only applies to items in {areaPathFilter}");
    logger.WriteInfo("Exiting");
    return;
}

if (!appliesToWorkItemTypes.Contains(self.WorkItemType))
{
    return $"Work item type was {self.WorkItemType}, so this rule will not be considered.";
}

var parent = self.Parent;
if (parent == null)
{
    return $"Work item has no parent, so this rule will not be considered.";
}

var children = parent.Children;
if (children.All(c => statesCausingParentClose.Contains(c.State)))
{
    if(!statesParentIsUnchangedIn.Contains(parent.State))
    {
        parent.State = closedState;
        parent.History = "All work completed, auto-finishing: ";
        logger.WriteInfo($"Aggregator changed {parent.WorkItemType} {parent.Id}: State = {parent.State}");
    }
    else
    {
        logger.WriteInfo($"Parent {parent.Id} has state {parent.State}. Parent was not changed.");
    }
}
else
{
    logger.WriteInfo($"Parent was not changed.");
}
return;

Expected behavior

A list of the children of the work item is returned.

Actual behavior

A 400 Bad Request is returned from the function, with the error:

One or more errors occurred. (VS403474: You requested 307 work items which exceeds the limit of 200)

Suspected cause

Looking into the code of the Aggregator, here's the Children property:

        public IEnumerable<WorkItemWrapper> Children
        {
            get
            {
                if (ChildrenLinks != null && ChildrenLinks.Any())
                {
                    var store = new WorkItemStore(_context);
                    return store.GetWorkItems(ChildrenLinks);
                }
                else
                    return new WorkItemWrapper[0];
            }
        }

And the GetWorkItems() method:

        public IList<WorkItemWrapper> GetWorkItems(IEnumerable<int> ids)
        {
            _context.Logger.WriteVerbose($"Getting workitems {ids.ToSeparatedString()}");
            return _context.Tracker.LoadWorkItems(ids, (workItemIds) =>
            {
                _context.Logger.WriteInfo($"Loading workitems {workItemIds.ToSeparatedString()}");
                var items = _clients.WitClient.GetWorkItemsAsync(workItemIds, expand: WorkItemExpand.All).Result;
                return items.ConvertAll(i => new WorkItemWrapper(_context, i));
            });
        }

GetWorkItemsAsync is doing the dirty work and seems to be the problem. This has been cited in the past as a limitation of GetWorkItemsAsync, and it may be that ADO introduced a limit to head off this problem. In any case, I would imagine it should be easy to correct by splitting the set of work item IDs into batches if there are more than 200 of them and combining the batches.

[giuliov]

Wow, I am curious about the scenario, as this is a limit on direct children.
Fixing shouldn't be hard, but I won't have much time in the next weeks.