feat: Add DateCoercer

lib/typed/coercion/coercer_registry.rb

@@ -17,6 +17,7 @@ class CoercerRegistry
           BooleanCoercer,
           IntegerCoercer,
           FloatCoercer,
+          DateCoercer,
           EnumCoercer,
           StructCoercer,
           TypedArrayCoercer

lib/typed/coercion/date_coercer.rb

@@ -0,0 +1,29 @@
+# typed: strict
+
+require "date"
+
+module Typed
+  module Coercion
+    class DateCoercer < Coercer
+      extend T::Generic
+
+      Target = type_member { {fixed: Date} }
+
+      sig { override.params(type: T::Types::Base).returns(T::Boolean) }
+      def used_for_type?(type)
+        T::Utils.coerce(type) == T::Utils.coerce(Date)
+      end
+
+      sig { override.params(type: T::Types::Base, value: Value).returns(Result[Target, CoercionError]) }
+      def coerce(type:, value:)
+        return Failure.new(CoercionError.new("Type must be a Date.")) unless used_for_type?(type)
+
+        return Success.new(value) if value.is_a?(Date)
+
+        Success.new(Date.parse(value))
+      rescue Date::Error, TypeError
+        Failure.new(CoercionError.new("'#{value}' cannot be coerced into Date."))
+      end
+    end
+  end
+end

test/typed/coercion/coercer_registry_test.rb

@@ -14,6 +14,6 @@ def test_register_prepends_coercer_so_it_overrides_built_in_ones
   end
 
   def test_when_type_doesnt_match_coercer_returns_nil
-    assert_nil(Typed::Coercion::CoercerRegistry.instance.select_coercer_by(type: T::Utils.coerce(Date)))
+    assert_nil(Typed::Coercion::CoercerRegistry.instance.select_coercer_by(type: T::Utils.coerce(BigDecimal)))
   end
 end

test/typed/coercion/date_coercer_test.rb

@@ -0,0 +1,31 @@
+# typed: true
+
+class DateCoercerTest < Minitest::Test
+  def setup
+    @coercer = Typed::Coercion::DateCoercer.new
+    @type = T::Utils.coerce(Date)
+  end
+
+  def test_used_for_type_works
+    assert(@coercer.used_for_type?(@type))
+    refute(@coercer.used_for_type?(T::Utils.coerce(Integer)))
+  end
+
+  def test_when_non_date_type_given_returns_failure
+    result = @coercer.coerce(type: T::Utils.coerce(Integer), value: Date.new(2024, 1, 1))
+
+    assert_failure(result)
+    assert_error(Typed::Coercion::CoercionError.new("Type must be a Date."), result)
+  end
+
+  def test_when_coercable_returns_success
+    assert_payload(Date.new(2024, 1, 1), @coercer.coerce(type: @type, value: "20240101"))
+    assert_payload(Date.new(2024, 5, 1), @coercer.coerce(type: @type, value: "1/5/2024"))
+    assert_payload(Date.new(2024, 5, 1), @coercer.coerce(type: @type, value: Date.new(2024, 5, 1)))
+  end
+
+  def test_when_not_coercable_returns_failure
+    assert_error(Typed::Coercion::CoercionError.new("'a' cannot be coerced into Date."), @coercer.coerce(type: @type, value: "a"))
+    assert_error(Typed::Coercion::CoercionError.new("'1' cannot be coerced into Date."), @coercer.coerce(type: @type, value: 1))
+  end
+end

test/typed/coercion_test.rb

@@ -1,6 +1,6 @@
 # typed: true
 
-require "date"
+require "bigdecimal"
 
 class CoercionTest < Minitest::Test
   def teardown
@@ -21,7 +21,7 @@ def test_when_coercer_is_matched_coerce_coerces
   end
 
   def test_when_coercer_isnt_matched_coerce_returns_failure
-    result = Typed::Coercion.coerce(type: T::Utils.coerce(Date), value: "testing")
+    result = Typed::Coercion.coerce(type: T::Utils.coerce(BigDecimal), value: "testing")
 
     assert_failure(result)
     assert_error(Typed::Coercion::CoercionNotSupportedError.new, result)