There's something unclear about this. MapSet should take care of duplication automatically. So:

1. Why is this not happening? (see https://elixir.hexdocs.pm/MapSet.html#put/2)

iex(1)> a = MapSet.new([%{type: "a", id: 1}])
MapSet.new([%{id: 1, type: "a"}])
iex(3)> MapSet.put(a, %{id: 1, type: "a"})
MapSet.new([%{id: 1, type: "a"}])
iex(5)> MapSet.union(a, a)
MapSet.new([%{id: 1, type: "a"}])

2. If MapSet isn't working for a valid reason, can we implement a solution that avoids enumerating the included list again? (e.g. using a map with a type {type, id} tuple as key to avoid duplicating entries)

@treere ideas?

Why is this not happening?

IIUC, the root cause would be in the normalize_resource_included logic, which only includes the relationship if it's loaded. This means that for the same {type, id} pair we could have two different objects (because the relationships are different), even though they effectively represent the same type.

I think that's MapSet's expected behaviour, but correct me if I'm missing something:

iex(1)> a = MapSet.new([%{type: "a", id: 1}])
MapSet.new([%{id: 1, type: "a"}])
iex(2)> b = MapSet.new([%{type: "a", id: 1, relationships: %{"company" => :loaded}}])
MapSet.new([%{id: 1, type: "a", relationships: %{"company" => :loaded}}])
iex(3)> MapSet.union(a, b)
MapSet.new([
  %{id: 1, type: "a"},
  %{id: 1, type: "a", relationships: %{"company" => :loaded}}
])

If MapSet isn't working for a valid reason, can we implement a solution that avoids enumerating the included list again? (e.g. using a map with a type {type, id} tuple as key to avoid duplicating entries)

I've tried implementing a solution with this approach, let me know if you had something different in mind. Thank you!

@ivan-sibilla there's an unused function. If you can fix it and test the changes work as intended for you we can merge and release an updated version

@lucacorti Removed the unused function and double checked that this should fix the problem we encountered. Thank you 🙏

@lucacorti Would you mind merging yourself? I don't have merge permissions.

@ivan-sibilla done, if you can test this against main in production I can then release a patch version.

@lucacorti Tested in production against the current revision on main, and the fix is working as intended; I think we can proceed with the patch version. Thank you so much!

@ivan-sibilla 2.0.4 is out including your changes. Thanks ❤️