Pay attention to not override properties when using a group by subquery

[noxan]

An example to retrieve a single object (movie) with a grouped multi link property (actors).

Warning: You must name the grouped property differently than the property itself else your query fails.

Given the following schema

type Actor {
  required name: str;
  required year: int16;
}

type Movie {
  required title: str;
  multi actors: Actor;
}

My attempt so far, but it fails due to actors overriding the actors property.

e.select(e.Movie, (movie) => ({
  title: true,
  actors: e.group(movie.actors, (actor) => ({ // <- here is the problem
    name: true,
    by: {year: actor.year},
  })),
}))

So use a different name than actors to make it work.

e.select(e.Movie, (movie) => ({
  title: true,
  actorsGrouped: e.group(movie.actors, (actor) => ({ // <- this is how it works
    name: true,
    by: {year: actor.year},
  })),
}))

Took me quite a while to understand my mistake, hope it will save you some time :)

Especially the in editor (vscode) type warnings are not very helpful unless you find the error message within all of this:

  Overload 1 of 6, '(expr: $expr_PathNode<TypeSet<$Movie, Cardinality.Many>, null>, shape: (scope: { __element__: $Movie; __cardinality__: Cardinality.One; __parent__: PathParent<...> | null; __kind__: ExpressionKind.PathNode; "*": { ...; }; } & { ...; } & {} & ExpressionMethods<...> & { ...; }) => Readonly<...>): $expr_Select<...>', gave the following error.
    Type '$expr_Group<$expr_PathNode<getChildOfObjectTypeSet<{ __element__: $Movie; __cardinality__: Cardinality.One; __parent__: PathParent<ObjectTypeSet, string> | null; __kind__: ExpressionKind.PathNode; "*": { ...; }; }, "actors">, { ...; }>, { ...; }, normaliseShape<...>>' is not assignable to type 'linkDescToSelectElement<LinkDesc<$Actor, Cardinality.Many, {}, false, false, false, false>> | undefined'.
      Type '$expr_Group<$expr_PathNode<getChildOfObjectTypeSet<{ __element__: $Movie; __cardinality__: Cardinality.One; __parent__: PathParent<ObjectTypeSet, string> | null; __kind__: ExpressionKind.PathNode; "*": { ...; }; }, "actors">, { ...; }>, { ...; }, normaliseShape<...>>' is not assignable to type 'linkDescToShape<LinkDesc<$Actor, Cardinality.Many, {}, false, false, false, false>>'.
        Type '$expr_Group<$expr_PathNode<getChildOfObjectTypeSet<{ __element__: $Movie; __cardinality__: Cardinality.One; __parent__: PathParent<ObjectTypeSet, string> | null; __kind__: ExpressionKind.PathNode; "*": { ...; }; }, "actors">, { ...; }>, { ...; }, normaliseShape<...>>' is not assignable to type 'Partial<{ id: propDescToSelectElement<PropertyDesc<$uuid, Cardinality.One, true, false, true, true>>; __type__: linkDescToSelectElement<LinkDesc<$ObjectType, ... 5 more ..., false>>; ... 5 more ...; "<actors": linkDescToSelectElement<...>; }>'.
          Types of property '"id"' are incompatible.
            Type '$expr_PathLeaf<getChildOfObjectTypeSet<{ __element__: ObjectType<"std::FreeObject", { id: PropertyDesc<$uuid, Cardinality.One, true, false, true, true>; __type__: LinkDesc<$ObjectType, ... 5 more ..., false>; } & { ...; }, { ...; }, ExclusiveTuple>; ... 4 more ...; __scope__: ObjectTypeSet; }, "id">, { ...; }>' is not assignable to type 'propDescToSelectElement<PropertyDesc<$uuid, Cardinality.One, true, false, true, true>> | undefined'.
              Type '$expr_PathLeaf<getChildOfObjectTypeSet<{ __element__: ObjectType<"std::FreeObject", { id: PropertyDesc<$uuid, Cardinality.One, true, false, true, true>; __type__: LinkDesc<$ObjectType, ... 5 more ..., false>; } & { ...; }, { ...; }, ExclusiveTuple>; ... 4 more ...; __scope__: ObjectTypeSet; }, "id">, { ...; }>' is not assignable to type 'TypeSet<$uuid, Cardinality.One>'.
                Types of property '__cardinality__' are incompatible.
                  Type 'Cardinality.Many' is not assignable to type 'Cardinality.One'.
  Overload 2 of 6, '(expr: PrimitiveTypeSet, modifiers: (expr: PrimitiveTypeSet) => Readonly<{ id: true; title: true; description: true; actors: $expr_Group<$expr_PathNode<getChildOfObjectTypeSet<{ __element__: $Movie; __cardinality__: Cardinality.One; __parent__: PathParent<...> | null; __kind__: ExpressionKind.PathNode; "*": { ...; }; }, "actors">, { ...; }>, { ...; }, normaliseShape<...>>; filter_single: $expr_Operator<...>; }>): $expr_Select<...>', gave the following error.
    Argument of type '$expr_PathNode<TypeSet<$Movie, Cardinality.Many>, null>' is not assignable to parameter of type 'PrimitiveTypeSet'.
      Types of property '__element__' are incompatible.
        Type '$Movie' is not assignable to type 'PrimitiveType'.
          Type 'ObjectType<"default::Movie", { id: PropertyDesc<$uuid, Cardinality.One, true, false, true, true>; __type__: LinkDesc<$ObjectType, Cardinality.One, ... 4 more ..., false>; description: PropertyDesc<...>; title: PropertyDesc<...>; actors: LinkDesc<...>; }, null, [...]>' is not assignable to type 'ScalarType<string, any, any, any> | EnumType<string, [string, ...string[]]> | TupleType<BaseTypeTuple> | NamedTupleType<NamedTupleShape>'.
            Type 'ObjectType<"default::Movie", { id: PropertyDesc<$uuid, Cardinality.One, true, false, true, true>; __type__: LinkDesc<$ObjectType, Cardinality.One, ... 4 more ..., false>; description: PropertyDesc<...>; title: PropertyDesc<...>; actors: LinkDesc<...>; }, null, [...]>' is not assignable to type 'NamedTupleType<NamedTupleShape>'.
              Types of property '__kind__' are incompatible.
                Type 'TypeKind.object' is not assignable to type 'TypeKind.namedtuple'.ts(2769)
default.ts(49, 3): The expected type comes from property 'actors' which is declared here on type 'Readonly<Partial<{ id: propDescToSelectElement<PropertyDesc<$uuid, Cardinality.One, true, false, true, true>>; __type__: linkDescToSelectElement<LinkDesc<...>>; description: propDescToSelectElement<...>; title: propDescToSelectElement<...>; actors: linkDescToSelectElement<...>; }> & { ...; } & SelectModifier...'
select.ts(972, 17): The call would have succeeded against this implementation, but implementation signatures of overloads are not externally visible.
(property) select: <$expr_PathNode<TypeSet<$Movie, Cardinality.Many>, null>, $Movie, Partial<{
    id: propDescToSelectElement<PropertyDesc<$uuid, Cardinality.One, true, false, true, true>>;
    __type__: linkDescToSelectElement<...>;
    description: propDescToSelectElement<...>;
    title: propDescToSelectElement<...>;
    actors: linkDescToSelectElement<...>;
}> & {
    ...;
} & SelectModifiers<...>, Cardinality.Many, normaliseShape<...>, {
    ...;
} & ... 3 more ... & {
    ...;
}, "default::Movie", Pick<...>>(expr: $expr_PathNode<...>, shape: (scope: {
    ...;
} & ... 3 more ... & {
    ...;
}) => Readonly<...>) => $expr_Select<...> (+5 overloads)```

[scotttrinh]

Yeah, the same is true for computeds, which is a pretty common gotcha with just as opaque of a type error. I'll look into adding some more guidance in the grouping docs to point out this gotcha.

[noxan]

would highly appreciate it, also the chatbot on the docs does make the very same mistake :D