Apply attrs' converter to default before omit_if_default check

Author: antony-frolov

src/cattrs/gen/__init__.py

@@ -4,7 +4,7 @@
 from collections.abc import Callable, Iterable, Mapping
 from typing import TYPE_CHECKING, Any, Final, Literal, TypeVar
 
-from attrs import NOTHING, Attribute, Factory
+from attrs import NOTHING, Attribute, Factory, Converter
 from typing_extensions import NoDefault
 
 from .._compat import (
@@ -178,15 +178,26 @@ def make_dict_unstructure_fn_from_attrs(
                 globs[def_name] = d.factory
                 internal_arg_parts[def_name] = d.factory
                 if d.takes_self:
-                    lines.append(f"  if instance.{attr_name} != {def_name}(instance):")
+                    def_str = f"{def_name}(instance)"
                 else:
-                    lines.append(f"  if instance.{attr_name} != {def_name}():")
-                lines.append(f"    res['{kn}'] = {invoke}")
+                    def_str = f"{def_name}()"
             else:
                 globs[def_name] = d
                 internal_arg_parts[def_name] = d
-                lines.append(f"  if instance.{attr_name} != {def_name}:")
-                lines.append(f"    res['{kn}'] = {invoke}")
+                def_str = def_name
+
+            c = a.converter
+            if isinstance(c, Converter):
+                conv_name = f"__c_conv_{attr_name}"
+                globs[conv_name] = c
+                internal_arg_parts[conv_name] = c
+                field_name = f"__c_field_{attr_name}"
+                globs[field_name] = a
+                internal_arg_parts[field_name] = a
+                def_str = f"{conv_name}({def_str}, instance, {field_name})"
+
+            lines.append(f"  if instance.{attr_name} != {def_str}:")
+            lines.append(f"    res['{kn}'] = {invoke}")
 
         else:
             # No default or no override.