PostGISPlugin.js

module.exports = function PostGisPlugin(builder) {
  builder.hook(
    'GraphQLObjectType:fields', 
    (
    fields, // Input object
    { extend, 
      pgGetGqlTypeByTypeId,
      pgIntrospectionResultsByKind: introspectionResultsByKind,
      pgSql: sql,
      pg2gql, 
      graphql: { GraphQLString },
      getAliasFromResolveInfo,
    }, // Build
    { scope: { isRootQuery } }
  ) => {
    if (!isRootQuery) {
      return fields;
    }

    addDataGenerator(parsedResolveInfoFragment => {
      const { alias } = parsedResolveInfoFragment;
      return {
        pgQuery: queryBuilder => {
          queryBuilder.select(
            sql.fragment`ST_AsGeoJSON(${sql.identifier(queryBuilder.getTableAlias(), attr.name)})`,
            alias
          );
        },
      };
    });


    return extend(fields, {
      geojson: {
        type: GraphQLString,
        resolve(data, _args, _context, resolveInfo) {
          const alias = getAliasFromResolveInfo(resolveInfo);
          return data[alias];
        }
      }

    });
  });
};