Field must be included in selection set when sorting in a nested selection about graphql

[danstarns]

Digging deeper - If we take the query that's failing:

{
  movies(where: { title_CONTAINS: "Matrix Reloaded, The" }) {
    title
    actors(options: { limit: 1 }) {
      name
      acted_in(options: { limit: 3, sort: { year: DESC } }) {
        title
      }
    }
  }
}

The cypher produced is:

MATCH (this:Movie)
WHERE this.title CONTAINS $this_title_CONTAINS

RETURN this {
  .title, 
  actors: [ (this)<-[:ACTED_IN]-(this_actors:Actor) | this_actors { 
      .name, 
      acted_in: apoc.coll.sortMulti([ (this_actors)-[:ACTED_IN]->(this_actors_acted_in:Movie) | this_actors_acted_in { .title } ], ['year'])[..3] 
  } ][..1] 
} AS this

Looking at what neo4j-graphql-js does... We should still project the property so it can be sorted on:

MATCH (this:Movie)
WHERE this.title CONTAINS $this_title_CONTAINS

RETURN this {
  .title, 
  actors: [ (this)<-[:ACTED_IN]-(this_actors:Actor) | this_actors { 
      .name, 
-     acted_in: apoc.coll.sortMulti([ (this_actors)-[:ACTED_IN]->(this_actors_acted_in:Movie) | this_actors_acted_in { .title } ], ['year'][..3],
+     acted_in: apoc.coll.sortMulti([ (this_actors)-[:ACTED_IN]->(this_actors_acted_in:Movie) | this_actors_acted_in { .title, .year } ], ['year'])[..3] 
  } ][..1] 
} AS this

This does mean that on particular usages, such as this issue raised, we are selecting a field that is not asked for and relying on the GraphQL runtime to filter out that field.

[danstarns]

@johnymontana Thanks for the clarity and steps to reproduce I can produce this locally also.

[johnymontana]

Right, it's an unfortunate consequence of using apoc.coll.sortMulti as a post-processing step of the pattern comprehension. If the Cypher pattern comprehension supported ordering then the additional field wouldn't need to be selected and the database would just take care of it.

There's an outstanding card to add this functionality to Cypher here, I'll ping that card with this example as another use case where it would make sense to add to Cypher.