Flatten graphql info using 'graphql-parse-resolve-info'

flatten.ts

import {FieldsByTypeName, parseResolveInfo, ResolveTree} from 'graphql-parse-resolve-info';



const parsedResolveInfoFragment = parseResolveInfo(info) as ResolveTree;


const curation = await ctx.prismaBinding.query.curation(
                    {
                        where: {
                            id: root.id,
                        },
                    },
                    ` { id 
                        content { 
                            book { __typename ${flattenToString(parsedResolveInfoFragment.fieldsByTypeName.Book)} } 
                            podcastEpisode { __typename ${flattenToString(parsedResolveInfoFragment.fieldsByTypeName.PodcastEpisode)} }
                            video { __typename ${flattenToString(parsedResolveInfoFragment.fieldsByTypeName.Video)} }
                            link { __typename ${flattenToString(parsedResolveInfoFragment.fieldsByTypeName.Link)} }
                            movie { __typename ${flattenToString(parsedResolveInfoFragment.fieldsByTypeName.Movie)} }
                            tvShow { __typename ${flattenToString(parsedResolveInfoFragment.fieldsByTypeName.TvShow)} }
                        }
                    }`,
                );

const union = curation.content.podcastEpisode ||
                    curation.content.video ||
                    curation.content.link ||
                    curation.content.movie ||
                    curation.content.book ||
                    curation.content.tvShow

function flattenToString(type: {[str: string]: ResolveTree}) {
    // return empty for null t  ype
    if(!type) {
        return ''
    }
    // loop through each field name

    return Object.keys(type)
        .map(value => type[value])
        .map(resolveTree => {
            const alias = resolveTree.alias;
            const typenameField = resolveTree.fieldsByTypeName;

            const result = Object.keys(typenameField).map(typename => flattenToString(typenameField[typename]));

            if (result.length > 0) {
                return ` ${alias} { ${result.join(' ')} } `;
            } else {
                return ` ${alias} `;
            }
        })
        .join(' ');
}

Can be used to turn Prisma types into Unions.