Add BitcrowdEcto.FixedWidthInteger

lib/bitcrowd_ecto/fixed_width_integer.ex

@@ -0,0 +1,56 @@
+defmodule BitcrowdEcto.FixedWidthInteger do
+  @moduledoc """
+  An Ecto type that automatically validates that the given integer fits the underlying DB type.
+
+  This turns the ugly Postgrex errors into neat `validation: :cast` changeset errors without
+  having to manually `validate_number` all `:integer` fields.
+
+  Named widths are based on Postgres' integer types.
+
+  https://www.postgresql.org/docs/current/datatype-numeric.html
+  """
+
+  use Ecto.ParameterizedType
+
+  @impl true
+  def init(opts) do
+    case Keyword.get(opts, :width, 4) do
+      2 -> -32_768..32_767
+      4 -> -2_147_483_648..2_147_483_647
+      8 -> -9_223_372_036_854_775_808..9_223_372_036_854_775_807
+      :smallint -> -32_768..32_767
+      :integer -> -2_147_483_648..2_147_483_647
+      :bigint -> -9_223_372_036_854_775_808..9_223_372_036_854_775_807
+      :smallserial -> 1..32_767
+      :serial -> 1..2_147_483_647
+      :bigserial -> 1..9_223_372_036_854_775_807
+    end
+  end
+
+  @impl true
+  def type(_range), do: :integer
+
+  @impl true
+  def cast(value, range) do
+    if is_integer(value) and value not in range do
+      :error
+    else
+      Ecto.Type.cast(:integer, value)
+    end
+  end
+
+  @impl true
+  def load(value, loader, _range) do
+    Ecto.Type.load(:integer, value, loader)
+  end
+
+  @impl true
+  def dump(value, dumper, _range) do
+    Ecto.Type.dump(:integer, value, dumper)
+  end
+
+  @impl true
+  def equal?(a, b, _range) do
+    a == b
+  end
+end

test/bitcrowd_ecto/fixed_width_integer_test.exs

@@ -0,0 +1,50 @@
+defmodule BitcrowdEcto.FixedWidthIntegerTest do
+  use ExUnit.Case, async: true
+  import BitcrowdEcto.Assertions
+  import Ecto.Changeset
+
+  defmodule TestSchema do
+    use Ecto.Schema
+
+    embedded_schema do
+      field(:int_4, BitcrowdEcto.FixedWidthInteger, width: 4)
+      field(:int_smallint, BitcrowdEcto.FixedWidthInteger, width: :smallint)
+      field(:int_bigserial, BitcrowdEcto.FixedWidthInteger, width: :bigserial)
+    end
+  end
+
+  test "casting an out-of-range value results in a changeset error" do
+    for ok <- [-2, 2, 0, -2_147_483_648, 2_147_483_647] do
+      cs = cast(%TestSchema{}, %{int_4: ok}, [:int_4])
+      assert cs.valid?
+    end
+
+    for not_ok <- [-2_147_483_649, 2_147_483_648] do
+      cs = cast(%TestSchema{}, %{int_4: not_ok}, [:int_4])
+      refute cs.valid?
+      assert_error_on(cs, :int_4, :cast)
+    end
+
+    for ok <- [-2, 2, 0, -32768, 32767] do
+      cs = cast(%TestSchema{}, %{int_smallint: ok}, [:int_smallint])
+      assert cs.valid?
+    end
+
+    for not_ok <- [-32769, 32768] do
+      cs = cast(%TestSchema{}, %{int_smallint: not_ok}, [:int_smallint])
+      refute cs.valid?
+      assert_error_on(cs, :int_smallint, :cast)
+    end
+
+    for ok <- [1, 9_223_372_036_854_775_807] do
+      cs = cast(%TestSchema{}, %{int_bigserial: ok}, [:int_bigserial])
+      assert cs.valid?
+    end
+
+    for not_ok <- [-1, 0, 9_223_372_036_854_775_808] do
+      cs = cast(%TestSchema{}, %{int_bigserial: not_ok}, [:int_bigserial])
+      refute cs.valid?
+      assert_error_on(cs, :int_bigserial, :cast)
+    end
+  end
+end