Exunit test error Ecto.Changeset.cast/4

Could you please share your AdminUser.common_changeset and whodoneit implementations?

But judging just by the error, you are using an atom MyTest.Whatwasit.Version instead of a struct %MyTest.Whatwasit.Version{} for the first argument in Ecto.Changeset.cast and it causes the match error.

Thank you @ruslandoga, Below are the details

In AdminUser.common_changeset :

def common_changeset(struct), do: common_changeset(struct, %{})

def common_changeset(struct, params) when is_map(params),
    do: common_changeset(struct, params, [])

def common_changeset(struct, opts) when is_list(opts), do: common_changeset(struct, %{}, opts)   
	   
def common_changeset(struct, params, opts) do
    max_length = Application.get_env(:my_test, :max_attribute_length) || 255
   
    struct
    |> email_changeset(params)
    |> cast(params, ~w[full_name roles groups availability_flag]a)
    |> validate_required(:full_name)
    |> validate_length(:full_name, max: max_length)
    |> put_roles
    |> put_groups
    |> prepare_version(opts)
end

whodoneit implementations :

def whodoneit(%User{} = user) do
    name =
      if user.first_name || user.last_name do
        [user.first_name, user.last_name]
        |> Enum.reject(&is_nil/1)
        |> Enum.join(" ")
      else
        user.email
      end

    [whodoneit: user, whodoneit_name: name]
  end

  def whodoneit(%AdminUser{} = admin) do
    [whodoneit_admin: admin, whodoneit_admin_name: admin.full_name]
  end

  def whodoneit(_), do: []
  def whodoneit, do: []

Also if I do inspect of Changeset, I am getting below result.

#Ecto.Changeset<
  action: nil,
  changes: %{roles: ["administrator"]},
  errors: [],
  data: #MyTest.AdminUser<>,
  valid?: true
>

Here Changeset valid is true, and I suspect issue is in Repo.update(changeset),
Please help to fix this issue.

It looks like your problem is with

It’s making another call to Ecto.Changeset.cast/4, but instead of passing a struct or changeset as the first argument, it’s passing the atom MyTest.Whatwasit.Version.

Hi @jswanner Could you please suggest the change in the above code to fix this.

The problem doesn’t look to be in the code you posted thus far. What does the code of MyTest.Whatwasit.Version look like?

Hi @jswanner , Below is the code for whatwasit_version.ex

def prepare_version(changeset, opts \\ []) do
    changeset
    |> Ecto.Changeset.prepare_changes(fn
      %{action: :update} = changeset ->
        insert_version(changeset, "update", opts)

      %{action: :delete} = changeset ->
        insert_version(changeset, "delete", opts)

      changeset ->
        changeset
    end)
  end

  
  def insert_version(changeset, action, opts) do
    {whodoneit_id, name} = get_whodoneit_name_and_id(opts)
    {whodoneit_admin_id, admin_name} = get_whodoneit_admin_name_and_id(opts)

    version_changeset(changeset, whodoneit_id, name, whodoneit_admin_id, admin_name, action)
    |> changeset.repo.insert!

    changeset
  end
  
  
  def version_changeset(struct, whodoneit_id, name, whodoneit_admin_id, admin_name, action) do
    version_module = @version_module

    model =
      case struct do
        %{data: data} -> data
        model -> model
      end

    type = item_type(model)

    user_id =
      cond do
        type == "User" -> model.id
        Map.has_key?(model, :user_id) -> Map.get(model, :user_id)
        true -> nil
      end

    version_module.module_changeset(version_module, %{
      item_type: type,
      item_id: model.id,
      item_user_id: user_id,
      object: model,
      action: "#{action}",
      whodoneit_id: whodoneit_id,
      whodoneit_name: name,
      whodoneit_admin_id: whodoneit_admin_id,
      whodoneit_admin_name: admin_name
    })
  end

Going back to your original stack trace:

We can see the error is raised when calling Ecto.Changeset.cast/4, which is called from MyTest.Whatwasit.Version.module_changeset/2 (not provided), which is called by MyTest.Whatwasit.Version.insert_version/3 (provided).

We can see the call to MyTest.Whatwasit.Version.module_changeset/2, the first argument is an atom (version_module):

We know from your original post that atom is being passed as the first argument to cast/4, but it should be a struct or a changeset. What we don’t yet know is where the struct is intended to be created from that atom.

If that module_changeset/2 function has code to create a struct in it, then you’ll need to figure out why it’s not happening. Otherwise, you could change the code in the version_changeset function to create a struct. Such as:

version_module.module_changeset(
  struct!(version_module),
  %{…}
)

Thank you so much for your quick response and support to fix this, It worked.

version_module.module_changeset(
  struct!(version_module),
  %{…}
)

Did you understand why does it work?