Support System.Collections.Immutable types

[latonz]

Support collection types in System.Collections.Immutable as mapping target types.
Eg. Mapperly should be able to implement a mapping from an IEnumerable<long> to an ImmutableList<int>.

[jamesfoster]

While this feature is not implemented is there a generic way to work around this?

Something like:

private static ImmutableList<TDest> ToImmutableList<TDest, TSource>(
    IEnumberable<TSource> source,
    Func<TSource, TDest> map
)
{
   return source.Select(map).ToImmutableList();
}

We can obviously add a workaround for each type but it doesn't seem to be possible to implement it generically.

[latonz]

Currently there is no support for generic user implemented mapping methods... I can't think of a feasible workaround 😢

[jamesfoster]

Thanks for the response. Without knowing too much about how source generators work, would it not be possible to support the suggested code? This could be useful for any generic type with a single type argument. if you know how to map from TSource to TDest you can supply a value for map. You can then use this method to map from any A<TSource> to a B<TDest>.

[TimothyMakkison]

Currently there is no support for generic user implemented mapping methods... I can't think of a feasible workaround 😢

I'll give it a go. Looks like EnumerableMappingBuilder.ResolveCollectMethodName can be used to add ToImmutableList etc. Not sure which immutable collections should be added aside from ImmutableList, ImmutableArray and ImmutableDictionary.

[latonz]

@TimothyMakkison nice 😊

The immutable collections are available in the immutable namespace. IMO Mapperly should probably support all generic implementations:

• ImmutableList<T>
• ImmutableArray<T>
• ImmutableHashSet<T>
• ImmutableQueue<T>
• ImmutableSortedSet<T>
• ImmutableDictionary <TKey, TValue>
• ImmutableSortedDictionary<TKey,TValue>

Some may need more effort than others, therefore it could make sense to split this up into multiple PR's.

[latonz]

@jamesfoster this could probably be a new feature of Mapperly. However, I think it adds a lot of complexity and I'm not sure if it justifies the added complexity.

[jamesfoster]

@jamesfoster this could probably be a new feature of Mapperly. However, I think it adds a lot of complexity and I'm not sure if it justifies the added complexity.

No worries. My use case was immutable collections anyway, and it looks like you're working on it. I can work around it for the time being by adding the non-generic mapper for each type as needed.

Thanks.

[latonz]

#305 implements support for the following immutable collections:

• ImmutableList<T>
• ImmutableArray<T>
• ImmutableHashSet<T>
• ImmutableQueue<T>
• ImmutableSortedSet<T>

Still missing:

• ImmutableDictionary<TKey, TValue>
• ImmutableSortedDictionary<TKey,TValue>

Thanks to @TimothyMakkison for the contribution 🎉

[latonz]

Thanks to another great contribution from @TimothyMakkison ImmutableDictionary<TKey, TValue> and ImmutableSortedDictionary<TKey,TValue> are now supported too.

[latonz]

This issue has been released in version 2.8.0-next.2 which is available on nuget.