Support nested structs

lib/typed/coercion/struct_coercer.rb

@@ -21,7 +21,41 @@ def coerce(type:, value:)
 
         return Failure.new(CoercionError.new("Value of type '#{value.class}' cannot be coerced to #{type} Struct.")) unless value.is_a?(Hash)
 
-        Success.new(T.cast(type, T::Types::Simple).raw_type.from_hash!(HashTransformer.new.deep_stringify_keys(value)))
+        values = {}
+
+        type = T.cast(type, T::Types::Simple)
+
+        type.raw_type.props.each do |name, prop|
+          attribute_type = prop[:type_object]
+          value = HashTransformer.new.deep_symbolize_keys(value)
+
+          if value[name].nil?
+            # if the value is nil but the type is nilable, no need to coerce
+            next if attribute_type.respond_to?(:valid?) && attribute_type.valid?(value[name])
+
+            return Typed::Failure.new(CoercionError.new("#{name} is required but nil given"))
+          end
+
+          # now that we've done the nil check, we can unwrap the nilable type to get the raw type
+          simple_attribute_type = attribute_type.respond_to?(:unwrap_nilable) ? attribute_type.unwrap_nilable : attribute_type
+
+          # if the prop is a struct, we need to recursively coerce it
+          if simple_attribute_type.respond_to?(:raw_type) && simple_attribute_type.raw_type <= T::Struct
+            Typed::HashSerializer
+              .new(schema: simple_attribute_type.raw_type.schema)
+              .deserialize(value[name])
+              .and_then { |struct| Typed::Success.new(values[name] = struct) }
+              .on_error { |error| return Typed::Failure.new(CoercionError.new("Nested hash for #{type} could not be coerced to #{name}, error: #{error}")) }
+          else
+            value = HashTransformer.new.deep_symbolize_keys(value)
+
+            Coercion
+              .coerce(type: attribute_type, value: value[name])
+              .and_then { |coerced_value| Typed::Success.new(values[name] = coerced_value) }
+          end
+        end
+
+        Success.new(type.raw_type.new(values))
       rescue ArgumentError, RuntimeError
         Failure.new(CoercionError.new("Given hash could not be coerced to #{type}."))
       end

test/typed/coercion/struct_coercer_test.rb

@@ -4,6 +4,7 @@ class StructCoercerTest < Minitest::Test
   def setup
     @coercer = Typed::Coercion::StructCoercer.new
     @type = T::Utils.coerce(Job)
+    @type_with_nested_struct = T::Utils.coerce(Person)
   end
 
   def test_used_for_type_works
@@ -51,6 +52,47 @@ def test_when_struct_cannot_be_coerced_returns_failure
     result = @coercer.coerce(type: @type, value: {"not" => "valid"})
 
     assert_failure(result)
-    assert_error(Typed::Coercion::CoercionError.new("Given hash could not be coerced to Job."), result)
+    assert_error(Typed::Coercion::CoercionError.new("title is required but nil given"), result)
+  end
+
+  def test_when_struct_has_nested_struct_and_all_values_passed_for_nested_struct
+    name = "Alex"
+    age = 31
+    ruby_rank = "pretty"
+    salary = 90_000_00
+    title = "Software Developer"
+    start_date = Date.new(2024, 3, 1)
+
+    result = @coercer.coerce(type: @type_with_nested_struct, value: {name:, age:, ruby_rank:, job: {title:, salary:, start_date:}})
+
+    person = Person.new(
+      name:,
+      age:,
+      ruby_rank: RubyRank.deserialize(ruby_rank),
+      job: Job.new(title:, salary:, start_date:)
+    )
+
+    assert_success(result)
+    assert_payload(person, result)
+  end
+
+  def test_when_struct_has_nested_struct_and_optional_start_date_not_passed_for_nested_struct
+    name = "Alex"
+    age = 31
+    ruby_rank = "pretty"
+    salary = 90_000_00
+    title = "Software Developer"
+
+    result = @coercer.coerce(type: @type_with_nested_struct, value: {name:, age:, ruby_rank:, job: {title:, salary:}})
+
+    person = Person.new(
+      name:,
+      age:,
+      ruby_rank: RubyRank.deserialize(ruby_rank),
+      job: Job.new(title:, salary:)
+    )
+
+    assert_success(result)
+    assert_payload(person, result)
   end
 end