A new validation library, looking for suggestions

Hi, would it be possible to build this library on top of Ecto’s schemaless changesets?

Could you write an example of expected behavior? @stefanchrobot

When I looked at the example on GitHub:

iex> schema = %{a: [:integer]}
%{a: [:integer]}
iex> data1 = %{a: 1}
%{a: 1}
iex> Joi.validate(data1, schema)
{:ok, %{a: 1}}
iex> data2 = %{a: <<123>>}
iex> Joi.validate(data2, schema)
{:error,
[
  %Joi.Error{
    context: %{key: :a, value: "{"},
    message: "a must be a integer",
    path: [:a],
    type: "integer.base"
  }
]}

the same - or at least similar - thing can be achieved using schemaless changesets with Ecto:

iex> types = %{a: :integer}
iex> data = %{a: "hello"}
iex> changeset = {%{}, types} |> Ecto.Changeset.cast(data, Map.keys(types))
#Ecto.Changeset<
  action: nil,
  changes: %{},
  errors: [a: {"is invalid", [type: :integer, validation: :cast]}],
  data: %{},
  valid?: false
>

So the question is whether the functionality you’re building can be written as an extension to Ecto, which is I think is very commonly used. In one of the previous projects, I had a microservice that didn’t have it’s own storage, but I still used Ecto to validate the schema of the incoming requests.