Pagination: clarify behavior of first/last calls.

[vslinko]

Copy of graphql/graphql-spec#104

I'm trying to implement pagination algorithm for my data and I don't know how to handle cases when first and last are negative.

What is your opinion about this?

ref: https://facebook.github.io/relay/graphql/connections.htm#sec-Pagination-algorithm

I think that spec should answer that question.

[josephsavona]

I agree with @leebyron's response in the original issue - first and last must be positive integers; this should be added to the Relay connection spec and graphql-relay-js's connection helper should throw on invalid first/last values.

Any interest in submitting a PR for this?

[vslinko]

I can submit PR for graphql-relay-js and I can try to submit to Relay spec, but I'm not sure about my English.

[josephsavona]

@BerndWessels this issue is about the semenatics of first/last calls and is largely resolved. Can you move your comment to #540?

[kassens]

Is there a reason not to allow 0? This might be useful for a case where you initially show no comments on an object and after pressing "see more comments" you increase from 0 upwards.

I would think we should update the spec and tests to non-negative. Thoughts?

[vslinko]

@kassens In current implementation first: 0 means "give me them all".
I think it isn't good decision and I agree with you that first: 0 could be helpful in some cases, so I can change my PRs.

@josephsavona what are you think?

[josephsavona]

I trust @kassens ;-)

My first thought was that first:0 would be the same as @include(if:false), but there might be fields on the connection that you want to fetch other than edges. Changing the semantics of first:0 to return zero edges makes sense, but we should verify that this won't impact products before making the change. Perhaps we could start with a warning in the writer if first is zero but edges are returned.

[KyleAMathews]

👍 to first: 0 just returning no edges. I'm an avid user of connectionFields and had been assuming I'd be able to use first: 0 when I wanted no edge results.

[dschafer]

Facebook's GraphQL servers throw an error when it receives either zero or a negative number. Having negative numbers throw an error is clearly the right call. I can go either way on zero; I very much like the current Facebook GraphQL server behavior since sending first: 0 is almost always an indication that the client didn't need to send that query, but I don't know if we need to express an error/empty opinion in the connection spec.

[wincent]

With 4eae620, I believe there's nothing left to do here. Thanks to everybody for contributing to the discussion!