pageInfo.hasPreviousPage always false when forward-paginating

[aloker]

When using forward pagination (first+after), pageInfo.hasPreviousPage always returns false.

The logic for calculating hasNextPage/hasPreviousPage is found in

relay/src/GraphQL.Relay/Types/ArraySliceMetrics.cs

Lines 47 to 75 in 4a1f935

	public ArraySliceMetrics(
	IList<TSource> slice,
	ResolveConnectionContext<TParent> context,
	int sliceStartIndex,
	int totalCount
	) {
	_items = slice;
	SliceSize = slice.Count;
	StartIndex = sliceStartIndex;
	var beforeOffset = ConnectionUtils.OffsetOrDefault(context.Before, totalCount);
	var afterOffset = ConnectionUtils.OffsetOrDefault(context.After, defaultOffset: -1);
	StartOffset = new[] {sliceStartIndex - 1, afterOffset, -1}.Max() + 1;
	EndOffset = new[] {EndIndex - 1, beforeOffset, totalCount}.Max();
	if (context.First.HasValue)
	EndOffset = Math.Min(EndOffset, StartOffset + context.First.Value);
	if (context.Last.HasValue)
	StartOffset = Math.Min(StartOffset, EndOffset - context.Last.Value);
	var lowerBound = context.After != null ? afterOffset + 1 : 0;
	var upperBound = context.Before != null ? beforeOffset : totalCount;
	HasPrevious = context.Last.HasValue && StartOffset > lowerBound;
	HasNext = context.First.HasValue && EndOffset < upperBound;
	}

Is this behavior intentional? Consider this query:

query {
  something(first:10 after:'SOMECURSOR') {
    pageInfo {
      startCursor
      hasPreviousPage      
    }
  }
} 

I would expect hasPreviousPage to be true IFF something(last:X before:startCursor) returns any results. However, it's always false.

The same goes for hasNextPage during backwards pagination, of course.

[jquense]

That does look like a bug! Care to investigate a bit closer and send a PR?

[aloker]

Sure, I'll have a look at it this evening

[aloker]

It has taken a bit longer, but hopefully the result is worth the wait.

[eddyjl077]

Hi,

In the version 0.5.0 the bug is still there, has this been fixed in the 0.6.0?

[CyrilleFormont]

Up

[nbarbettini]

The official package GraphQL.Relay hasn't been published since #24 was merged, so it looks to me like it's been fixed but not released.