Handle mapping struct fields with subtypes to Objective-C (#319)

stone/backends/swift_rsrc/ObjcTypes.jinja

@@ -22,7 +22,37 @@ public class DBX{{ namespace_class_name }}{{ data_type_class_name }}: {{ 'NSObje
     {% for field in data_type.fields %}
     {{ struct_field_doc(field, '    ') }}
     @objc
-    public var {{ fmt_var(field.name) }}: {{ fmt_objc_type(field.data_type) }} { {{ objc_return_field_value(data_type, field) }} }
+    {% if objc_return_field_value_specified_in_jinja(field) %}
+    public var {{ fmt_var(field.name) }}: {{ fmt_objc_type(field.data_type) }} {
+        {% if (field_is_user_defined(field)) or (field_is_user_defined_optional(field)) %}
+        switch {{ swift_var_name }}.{{ fmt_var(field.name) }} {
+        {% for tuple in objc_return_field_value_type_tuples(field) %}
+        case let {{ tuple[0] }} as {{ tuple[1] }}:
+            return {{ tuple[2] }}(swift: {{ tuple[0] }})
+        {% endfor %}
+        default:
+            {% if field_is_user_defined_optional(field) %}
+            return {{ swift_var_name }}.{{ fmt_var(field.name) }}.flatMap { {{ fmt_objc_type(field.data_type, False) }}(swift: $0) }
+            {% else %}
+            return {{ fmt_objc_type(field.data_type) }}(swift: {{ swift_var_name }}.{{ fmt_var(field.name) }})
+            {% endif %}
+        }
+        {% elif (field_is_user_defined_map(field)) or (field_is_user_defined_list(field)) %}
+        {{ swift_var_name }}.{{ fmt_var(field.name) }}.{{ 'mapValues' if field_is_user_defined_map(field) else 'map' }} {
+            switch $0 {
+            {% for tuple in objc_return_field_value_type_tuples(field) %} {#extract this snippet?#}
+            case let {{ tuple[0] }} as {{ tuple[1] }}:
+                return {{ tuple[2] }}(swift: {{ tuple[0] }})
+            {% endfor %}
+            default:
+                return {{ fmt_objc_type(field.data_type.data_type) }}(swift: $0)
+            }
+        }
+        {% endif %}
+    }
+    {% else %}
+    public var {{ fmt_var(field.name) }}: {{ fmt_objc_type(field.data_type) }} { {{ objc_return_field_value_oneliner(data_type, field) }} }
+    {% endif %}
     {% endfor %}
     {% if data_type.fields %}
 

stone/backends/swift_types.py

@@ -176,7 +176,16 @@ def generate(self, api):
         template_globals['data_objc_type_doc'] = self._data_objc_type_doc
         template_globals['objc_init_args'] = self._objc_init_args
         template_globals['fmt_objc_type'] = fmt_objc_type
-        template_globals['objc_return_field_value'] = self._objc_return_field_value
+        oneliner_func_key = 'objc_return_field_value_oneliner'
+        template_globals[oneliner_func_key] = self._objc_return_field_value_oneliner
+        template_globals['field_is_user_defined'] = self._field_is_user_defined
+        template_globals['field_is_user_defined_optional'] = self._field_is_user_defined_optional
+        template_globals['field_is_user_defined_list'] = self._field_is_user_defined_list
+        template_globals['field_is_user_defined_map'] = self._field_is_user_defined_map
+        in_jinja_key = 'objc_return_field_value_specified_in_jinja'
+        template_globals[in_jinja_key] = self._objc_return_field_value_specified_in_jinja
+        field_value_tuples_key = 'objc_return_field_value_type_tuples'
+        template_globals[field_value_tuples_key] = self._objc_return_field_value_type_tuples
         template_globals['objc_init_args_to_swift'] = self._objc_init_args_to_swift
         template_globals['objc_union_arg'] = self._objc_union_arg
         template_globals['objc_swift_var_name'] = self._objc_swift_var_name
@@ -334,7 +343,67 @@ def _route_schema_attrs(self, route_schema, route):
         result = ',\n                                    '.join(attrs)
         return result
 
-    def _objc_return_field_value(self, parent_type, field):
+    # List[typing.Tuple[let_name: str, swift_type: str, objc_type: str]]
+    def _objc_return_field_value_type_tuples(self, field):
+        data_type = field.data_type
+        ret = []
+
+        # if list type get the data type of the item
+        if is_list_type(data_type):
+            data_type = data_type.data_type
+
+        # if map type get the data type of the value
+        if is_map_type(data_type):
+            data_type = data_type.value_data_type
+
+        # if data_type is a struct type and has subtypes, process them into labels and types
+        if is_struct_type(data_type) and data_type.has_enumerated_subtypes():
+            all_subtypes = data_type.get_all_subtypes_with_tags()
+
+            for subtype in all_subtypes:
+                # subtype[0] is the tag name and subtype[1] is the subtype struct itself
+                struct = subtype[1]
+                case_let_name = fmt_var(struct.name)
+                swift_type = fmt_type(struct)
+                objc_type = fmt_objc_type(struct)
+                ret.append((case_let_name, swift_type, objc_type))
+
+        return ret
+
+    def _field_is_user_defined(self, field):
+        data_type, nullable = unwrap_nullable(field.data_type)
+        return is_user_defined_type(data_type) and not nullable
+
+    def _field_is_user_defined_optional(self, field):
+        data_type, nullable = unwrap_nullable(field.data_type)
+        return is_user_defined_type(data_type) and nullable
+
+    def _field_is_user_defined_map(self, field):
+        data_type, _ = unwrap_nullable(field.data_type)
+        return is_map_type(data_type) and is_user_defined_type(data_type.value_data_type)
+
+    def _field_is_user_defined_list(self, field):
+        data_type, _ = unwrap_nullable(field.data_type)
+        if is_list_type(data_type):
+            list_data_type, _ = unwrap_nullable(data_type.data_type)
+            return is_user_defined_type(list_data_type)
+        else:
+            return False
+
+    def _objc_return_field_value_specified_in_jinja(self, field) -> bool:
+        eligible_kind = self._field_is_user_defined(field) or \
+            self._field_is_user_defined_optional(field) or \
+            self._field_is_user_defined_map(field) or \
+            self._field_is_user_defined_list(field)
+
+        if not eligible_kind:
+            return False
+
+        requires_iterating_over_subtypes = len(self._objc_return_field_value_type_tuples(field)) > 0
+
+        return requires_iterating_over_subtypes
+
+    def _objc_return_field_value_oneliner(self, parent_type, field):
         data_type, nullable = unwrap_nullable(field.data_type)
         swift_var_name = self._objc_swift_var_name(parent_type)