Node & edges connection types are nullable

[Wenzil]

Currently, typings indicate that the node type of a connection must be nullable. It would be nice if it could be made non-nullable:

const MyConnection = connectionDefinitions({
    nodeType: new GraphQLNonNull(MyNodeType)
});

On the other hand, I feel like the edges field of a connection should always be a non-nullable list. E.g. it should have the type [SomeEdgeType]! rather than [SomeEdgeType]. My reasoning is that a connection with no edges should represent this with an empty list, and not a null value.

Similarly, each edge should be non-nullable. E.g. it should have the type SomeEdgeType! rather than SomeEdgeType.

In short, current connection types look like this:

type MyConnection {
  edges: [{
    node: NodeType
  }]
  pageInfo: { ... }!
}

and it could be improved to:

type MyConnection {
  edges: [{
    node: NodeType! // Nullability is parametrizable
  }!]!
  pageInfo: { ... }!
}

[cliedeman]

I am also interested in this.

btw it can currently be done with some minor copy-pasting with the current version:

  const edgeType = new GraphQLObjectType({
    name: `${name}Edge`,
    description: 'An edge in a connection.',
    fields: () => ({
      node: {
        type: new GraphQLNonNull(nodeType),
        resolve: resolveNode,
        description: 'The item at the end of the edge',
      },
      cursor: {
        type: new GraphQLNonNull(GraphQLString),
        resolve: resolveCursor,
        description: 'A cursor for use in pagination',
      },
    }),
  });

  const { connectionType } = connectionDefinitions({
    name,
    nodeType: new GraphQLNonNull(nodeType),
    connectionFields: {
      edges: {
        type: new GraphQLNonNull(new GraphQLList(new GraphQLNonNull(edgeType))),
      },
    },
  });

I started with a PR to make this more seamless but ran into typing issues changing the nodeType from GraphQLObjectType to GraphQLType to allow accepting the new GraphQLNonNull(nodeType). Will try again soon

[maxaggedon]

I would also be interested in this. As I use connectionFromArray to resolve my connections and it always returns an object with an edges property containing a non-nullable array.

[jaydenseric]

According to the spec, edges must be nullable:

This field must return a list type that wraps an edge type …
— https://facebook.github.io/relay/graphql/connections.htm#sec-Edges

Nodes may be either nullable or non-nullable:

This field must return either a Scalar, Enum, Object, Interface, Union, or a Non‐Null wrapper around one of those types.
— https://facebook.github.io/relay/graphql/connections.htm#sec-Node

[jaydenseric]

Keep in mind that if the node is non-nullable and it has an error resolving the whole edge is invalidated, a point raised here #103 (comment).

[IvanGoncharov]

Nodes are fixed in #302