Elixir: assert does work properly for structs

[almeynman]

Today I have upgraded to elixir 1.2.5 and for some reasom the following test failed:

test "registration's to_user function generates user with device and phone associations" do
    changeset = Registration.changeset(%Registration{}, @valid_attrs)
    registration = Ecto.Changeset.apply_changes(changeset)
    user = Registration.to_user(registration)
    assert struct(MyApp.Device, @valid_attrs) in user.devices
    assert struct(MyApp.Phone, @valid_attrs) in user.phones
  end

I receive the following error:

Assertion with in failed
     code: struct(MyApp.Device, @valid_attrs) in user.devices()
     lhs:  %MyApp.Device{__meta__: #Ecto.Schema.Metadata<:built>, id: nil,
            inserted_at: nil, updated_at: nil,
            user: #Ecto.Association.NotLoaded<association :user is not loaded>,
            user_id: nil, uuid: "599F9C00-92DC-4B5C-9464-7971F01F8370"}
     rhs:  [%MyApp.Device{__meta__: #Ecto.Schema.Metadata<:built>, id: nil,
             inserted_at: nil, updated_at: nil,
             user: #Ecto.Association.NotLoaded<association :user is not loaded>,
             user_id: nil, uuid: "599F9C00-92DC-4B5C-9464-7971F01F8370"}]

However when I change test to

   ...
    assert struct(MyApp.Device, Map.from_struct(registration)) in user.devices
    assert struct(MyApp.Phone, Map.from_struct(registration)) in user.phones

Test passes.

to_user function is pretty simple:

  def to_user(registration) do
    %MyApp.User{
      devices: [struct(MyApp.Device, Map.from_struct(registration))],
      phones: [struct(MyApp.Phone, Map.from_struct(registration))]
    }
  end

So is it a bug? or do I misunderstand something?

[josevalim]

@almasakchabayev it is very likely not a bug. There is certainly one of the fields that are still different. I would try the following:

dev1 = struct(MyApp.Device, @valid_attrs)
[dev2] = user.devices

assert dev1.id == dev2.id
assert dev1.__meta__ == dev2.__meta__
... and so on for all fields ...

And try to find which one does not match. This is probably a bug in Ecto. We may be hiding too much information.

[almeynman]

@josevalim Thanks for quick reply. It appears that error happens in __meta__:

[device1 | _] = user.devices
    device2 = struct(Typi.Device, @valid_attrs)
    assert device1.__meta__ == device2.__meta__
    assert device1.id == device2.id
    assert device1.inserted_at == device2.inserted_at
    assert device1.updated_at == device2.updated_at
    assert device1.user == device2.user
    assert device1.user_id == device2.user_id
    assert device1.uuid == device2.uuid

Assertion with == failed
     code: device1.__meta__() == device2.__meta__()
     lhs:  #Ecto.Schema.Metadata<:built>
     rhs:  #Ecto.Schema.Metadata<:built>

without __meta__ no errors

[whatyouhide]

@almasakchabayev can you paste the result of inspecting the Ecto.Schema.Metadata structs in your test? Be sure to use IO.inspect(meta, structs: false) so you get what's inside the struct :)

[josevalim]

Can you please call Map.from_struct on both metas before comparing them so
we know what is different?

On Monday, May 23, 2016, Almas Akchabayev [email protected] wrote:

@josevalim https://github.com/josevalim Thanks for quick reply. It
appears that error happens in meta:

[device1 | _] = user.devices
device2 = struct(Typi.Device, @valid_attrs)
assert device1.__meta__ == device2.meta
assert device1.id == device2.id
assert device1.inserted_at == device2.inserted_at
assert device1.updated_at == device2.updated_at
assert device1.user == device2.user
assert device1.user_id == device2.user_id
assert device1.uuid == device2.uuid

Assertion with == failed
code: device1.meta() == device2.meta()
lhs: #Ecto.Schema.Metadata<:built>
rhs: #Ecto.Schema.Metadata<:built>

without meta no errors

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_José Valimwww.plataformatec.com.br
http://www.plataformatec.com.br/Founder and Director of R&D_

[whatyouhide]

Map.from_struct/1 is a better choice, we'll get the nice assertion formatting :)

[almeynman]

@josevalim @whatyouhide I did

    assert Map.from_struct(device1.__meta__) == Map.from_struct(device2.__meta__)

and got the following error:

Assertion with == failed
     code: Map.from_struct(device1.__meta__()) == Map.from_struct(device2.__meta__())
     lhs:  %{context: nil, source: {nil, "registrations"}, state: :built}
     rhs:  %{context: nil, source: {nil, "devices"}, state: :built}

[josevalim]

So that's the issue. You are merging registration metadata into the device.
I will improve the metadata to make those clearer on Ecto side, thank you.

On Monday, May 23, 2016, Almas Akchabayev [email protected] wrote:

@josevalim https://github.com/josevalim @whatyouhide
https://github.com/whatyouhide I did

assert Map.from_struct(device1.__meta__) == Map.from_struct(device2.__meta__)

and got the following error:

Assertion with == failed
code: Map.from_struct(device1.meta()) == Map.from_struct(device2.meta())
lhs: %{context: nil, source: {nil, "registrations"}, state: :built}
rhs: %{context: nil, source: {nil, "devices"}, state: :built}

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_José Valimwww.plataformatec.com.br
http://www.plataformatec.com.br/Founder and Director of R&D_

[almeynman]

@josevalim @whatyouhide Also I remembered how this error appeared. I had Registration model as embedded_schema (followed your post) and then changed it to schema "registrations" do. When I change it back to embedded no errors appear

[almeynman]

@josevalim So I cannot write struct(MyApp.Device, Map.from_struct(registration)) in

def to_user(registration) do
    %MyApp.User{
      devices: [struct(MyApp.Device, Map.from_struct(registration))],
      phones: [struct(MyApp.Phone, Map.from_struct(registration))]
    }
  end

As it merges registrations metadata, right? What should I do instead though?

[josevalim]

Right. I think there is a function in the Ecto module that would discard
the metadata field but I am not sure and I don't remember which. :) (I am
not at the computer right now).

On Monday, May 23, 2016, Almas Akchabayev [email protected] wrote:

@josevalim https://github.com/josevalim So I cannot write struct(MyApp.Device,
Map.from_struct(registration)) in

def to_user(registration) do
%MyApp.User{
devices: [struct(MyApp.Device, Map.from_struct(registration))],
phones: [struct(MyApp.Phone, Map.from_struct(registration))]
}
end

As it merges registrations metadata, right?

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_José Valimwww.plataformatec.com.br
http://www.plataformatec.com.br/Founder and Director of R&D_

[josevalim]

Fixed in Ecto master. Apparently the function I mentioned above does not exist, you will have to delete the meta field explicitly for now.

[almeynman]

@josevalim I will just grab ecto master. Thanks

[almeynman]

@josevalim I updated deps to Ecto master, but the error still exists

[josevalim]

the error will still exist the difference is that you will be able to find out what is different between the two meta structs now.

[almeynman]

@josevalim So would something like that be enough:

  def to_map(registration) do
    registration
    |> Map.from_struct
    |> Map.delete(:__meta__)
  end

[josevalim]

Yes.