feat: Add BooleanCoercer

lib/typed/coercion/boolean_coercer.rb

@@ -0,0 +1,31 @@
+# typed: strict
+
+module Typed
+  module Coercion
+    class BooleanCoercer < Coercer
+      extend T::Generic
+
+      Target = type_member { {fixed: T::Boolean} }
+
+      sig { override.params(type: Field::Type).returns(T::Boolean) }
+      def used_for_type?(type)
+        type == T::Utils.coerce(T::Boolean)
+      end
+
+      sig { override.params(field: Field, value: Value).returns(Result[Target, CoercionError]) }
+      def coerce(field:, value:)
+        if T.cast(field.type, T::Types::Base).valid?(value)
+          Success.new(value)
+        elsif value == "true"
+          Success.new(true)
+        elsif value == "false"
+          Success.new(false)
+        else
+          Failure.new(CoercionError.new)
+        end
+      rescue TypeError => e
+        Failure.new(CoercionError.new("Field type must be a T::Boolean."))
+      end
+    end
+  end
+end

lib/typed/coercion/coercer_registry.rb

@@ -11,7 +11,7 @@ class CoercerRegistry
 
       Registry = T.type_alias { T::Array[T.class_of(Coercer)] }
 
-      DEFAULT_COERCERS = T.let([StringCoercer, IntegerCoercer, FloatCoercer, EnumCoercer, StructCoercer], Registry)
+      DEFAULT_COERCERS = T.let([StringCoercer, BooleanCoercer, IntegerCoercer, FloatCoercer, EnumCoercer, StructCoercer], Registry)
 
       sig { void }
       def initialize

test/typed/coercion/boolean_coercer_test.rb

@@ -0,0 +1,41 @@
+# typed: true
+
+class BooleanCoercerTest < Minitest::Test
+  def setup
+    @coercer = Typed::Coercion::BooleanCoercer.new
+    @field = Typed::Field.new(name: :capital, type: T::Utils.coerce(T::Boolean))
+  end
+
+  def test_used_for_type_works
+    assert(@coercer.used_for_type?(T::Utils.coerce(T::Boolean)))
+    refute(@coercer.used_for_type?(Integer))
+  end
+
+  def test_when_boolean_field_given_returns_failure
+    result = @coercer.coerce(field: Typed::Field.new(name: :testing, type: Integer), value: "testing")
+
+    assert_failure(result)
+    assert_error(Typed::Coercion::CoercionError.new("Field type must be a T::Boolean."), result)
+  end
+
+  def test_when_true_boolean_can_be_coerced_returns_success
+    result = @coercer.coerce(field: @field, value: "true")
+
+    assert_success(result)
+    assert_payload(true, result)
+  end
+
+  def test_when_false_boolean_can_be_coerced_returns_success
+    result = @coercer.coerce(field: @field, value: "false")
+
+    assert_success(result)
+    assert_payload(false, result)
+  end
+
+  def test_when_enum_cannot_be_coerced_returns_failure
+    result = @coercer.coerce(field: @field, value: "bad")
+
+    assert_failure(result)
+    assert_error(Typed::Coercion::CoercionError.new, result)
+  end
+end