nimble_options 1.1.1: Show the failure mode for NimbleOptions custom validators when the callback returns the wrong shape.

Found a cached public sample hit: `sha256:41ea393de638c575f2f87f965ec5c0d67ac71f5700421b440ef9ae4eae3ec768`, which covers unknown-key/type/required/nested-key error-message behavior.
I used a different NimbleOptions trap: `{:custom, mod, fun, args}` callback return-shape behavior.
Wrong version drift would fail loudly (instead of green), because the public sample proves the newer 1.1.1 family returns `%NimbleOptions.ValidationError{}` while older versions differ in validate failure shape and message layout.

{"case":{"believed":"A custom type callback is expected to return an error tuple and still be reported as {:error, ValidationError}; anything else should do the same.","caseId":"case:sha256:4e43ab01c15c9aab880b3113a46bf0f5e03c15889bd58ee8f7ecba604640f03a","contract":["assert NimbleOptions.validate([port: \"8080\"], custom_schema()) returns {:ok, [port: 8080]} while NimbleOptions.validate([port: :bad], custom_schema()) returns {:error, %NimbleOptions.ValidationError{message: \"invalid value for :port option: expected integer value in :port, got: :bad\"}}","assert NimbleOptions.validate([port: :bad], custom_schema()) converts {:error, message} from the callback into a NimbleOptions.ValidationError whose message is prefixed with the library error field","assert NimbleOptions.validate([port: \"8080\"], invalid_schema()) raises RuntimeError because the callback returns a non-conforming value"],"goal":"Show the failure mode for NimbleOptions custom validators when the callback returns the wrong shape.","kind":"HOW","packages":["pkg:hex/nimble_options@1.1.1"],"schemaVersion":1,"symbols":["NimbleOptions.validate","NimbleOptions.ValidationError"]},"contractCommand":["elixir","test/contract.exs"],"environment":{"arch":"x64","ecosystem":"hex","executionContext":"elixir","language":"elixir","os":"linux","packageManager":"mix","runtime":"elixir","schemaVersion":1},"license":"MIT-0","packages":["pkg:hex/nimble_options@1.1.1"],"schemaVersion":1,"symbols":["NimbleOptions.validate","NimbleOptions.ValidationError"],"verifierAdapter":"hex@1"}

ExUnit.start()


defmodule CustomValidatorContract do
  defmodule Validators do
    def parse_port(value) when is_integer(value), do: {:ok, value}

    def parse_port(value) when is_binary(value) do
      case Integer.parse(value) do
        {number, ""} -> {:ok, number}
        _ -> {:error, "expected integer value, got: #{inspect(value)}"}
      end
    end

    def parse_port(value), do: {:error, "expected integer value, got: #{inspect(value)}"}

    def bad_behavior(_value), do: :not_a_contract_tuple
  end

  def custom_schema do
    [port: [type: {:custom, __MODULE__.Validators, :parse_port, []}]]
  end

  def invalid_schema do
    [port: [type: {:custom, __MODULE__.Validators, :bad_behavior, []}]]
  end
end


defmodule CustomValidatorContractTest do
  use ExUnit.Case

  alias NimbleOptions.ValidationError

  test "custom callbacks can coerce values and emit a ValidationError shape" do
    assert NimbleOptions.validate([port: "8080"], CustomValidatorContract.custom_schema()) ==
             {:ok, [port: 8080]}

    assert {:error, %ValidationError{} = error} =
             NimbleOptions.validate([port: :bad], CustomValidatorContract.custom_schema())

    assert Exception.message(error) ==
             "invalid value for :port option: expected integer value, got: :bad"
  end

  test "custom callbacks must return {:ok, value} or {:error, message}" do
    assert_raise RuntimeError, ~r/must return .*\{:ok, value\} or \{:error, message\}/, fn ->
      NimbleOptions.validate([port: "8080"], CustomValidatorContract.invalid_schema())
    end
  end
end

ExUnit.run()