Feature: empty_values option

[jekku]

What's here?

• A new opt is added along with :optional? which allows us to declare what kind of values are considered to be empty
• Let's take into consideration the following declaration example:

defmodule Wallet do
  import DataSchema, only: [data_schema: 1]

  data_schema(
    field:
    {:account_number, "account_number", &DataSchemaTest.to_stringg/1,
     [optional?: false, empty_values: ["", nil, :undefined]]},
  )
end

Declaring Wallets with an account number, among any of ["", nil, :undefined] will cause an error.

iex(1)> DataSchema.to_struct(%{account_number: :undefined}, Wallet)
 {:error,
  %DataSchema.Errors{
    errors: [
      account_number: "Field was marked as not null but was found to be null."
    ]
  }}

Rundown of changes

• The preprocessor of DataSchema.to_struct/5 now takes all the opts (as keywords) and transforms them to a map. Sensible defaults are provided when some opts are not provided. This enforces matches in the private functions that process the fields.

• Elixir is updated to 1.13 (I cannot make it run with the current version for some reason)

• Some conditionals have been flattened

• A new error for required empty values has been added

[ulissesalmeida]

@Adzz should/can we change the null error message as well?

From

Field was marked as not null but was found to be null.

To be something like

Field was marked as not optional but was found to be #{inspect(value_found)}.

[jekku]

The error type should change as well after the draft.

It's currently:

%DataSchema.Errors.null_error{}

I imagine it to be something along the lines of:

%DataSchema.Errors.empty_required_value_error{}

[Adzz]

should/can we change the null error message as well?

The error type should change as well

Yes please! ❤️

[Adzz]

Small non blocking comment but great work overall, thanks!