No error on length validation of a {:array, :string} schema field when list is empty

Questions / Help
1

Here’s my field:

typed_schema "onboardings" do
  field(:mood_influencers, {:array, :string}, default: [])
  timestamps(type: :utc_datetime_usec)
end

And my changeset:

|> validate_required([
  :user_id,
  :mood_influencers,
])
|> validate_length(:mood_influencers, min: 1, max: 12)
|> validate_subset(:mood_influencers, [
  "A",
  "B",
  "C"
])

But when no my {:array, :string} field is empty (no selected checkboxes), there is no changeset error.

#Ecto.Changeset<
  action: nil,
  changes: %{
    mood_rating: 5,
    motivation_rating: "Somewhat Motivated",
    positivity_boost_will_work: "Yes"
  },
  errors: [user_id: {"can't be blank", [validation: :required]}],
  data: #App.Programs.Onboarding<>,
  valid?: false
>

I’m looking for an error that is like: “You need to select at least one item from the list of options.”

I thought validates_required would take care of this.

2

validate_required is specifically looking for nil and "":

On the other hand, validate_length is built on top of validate_change so it won’t even be invoked if mood_influencers isn’t changed from the default [].