1 files changed, 113 insertions, 0 deletions
diff --git a/debian/lib/python/debian_linux/dataclasses_extra.py b/debian/lib/python/debian_linux/dataclasses_extra.py
new file mode 100644
index 000000000..49f241003
--- /dev/null
+++ b/debian/lib/python/debian_linux/dataclasses_extra.py
@@ -0,0 +1,113 @@
+from __future__ import annotations
+
+from dataclasses import (
+    fields,
+    is_dataclass,
+    replace,
+)
+from typing import (
+    Protocol,
+    TypeVar,
+    TYPE_CHECKING,
+)
+
+if TYPE_CHECKING:
+    from _typeshed import DataclassInstance as _DataclassInstance
+
+    class _HasName(Protocol, _DataclassInstance):
+        name: str
+
+    _DataclassT = TypeVar('_DataclassT', bound=_DataclassInstance)
+    _HasNameT = TypeVar('_HasNameT', bound=_HasName)
+
+
+def default(
+    cls: type[_DataclassT],
+    /,
+) -> _DataclassT:
+    f = {}
+
+    for field in fields(cls):
+        if 'default' in field.metadata:
+            f[field.name] = field.metadata['default']
+
+    return cls(**f)
+
+
+def merge(
+    self: _DataclassT,
+    other: _DataclassT | None, /,
+) -> _DataclassT:
+    if other is None:
+        return self
+
+    f = {}
+
+    for field in fields(self):
+        if not field.init:
+            continue
+
+        field_default_type = object
+        if isinstance(field.default_factory, type):
+            field_default_type = field.default_factory
+
+        self_field = getattr(self, field.name)
+        other_field = getattr(other, field.name)
+
+        if field.name == 'name':
+            assert self_field == other_field
+        elif field.type == 'bool':
+            f[field.name] = other_field
+        elif field.metadata.get('merge') == 'assoclist':
+            f[field.name] = _merge_assoclist(self_field, other_field)
+        elif is_dataclass(field_default_type):
+            f[field.name] = merge(self_field, other_field)
+        elif issubclass(field_default_type, list):
+            f[field.name] = self_field + other_field
+        elif issubclass(field_default_type, dict):
+            f[field.name] = self_field | other_field
+        elif field.default is None:
+            if other_field is not None:
+                f[field.name] = other_field
+        else:
+            raise RuntimeError(f'Unable to merge for type {field.type}')
+
+    return replace(self, **f)
+
+
+def merge_default(
+    cls: type[_DataclassT],
+    /,
+    *others: _DataclassT,
+) -> _DataclassT:
+    ret: _DataclassT = default(cls)
+    for o in others:
+        ret = merge(ret, o)
+    return ret
+
+
+def _merge_assoclist(
+    self_list: list[_HasNameT],
+    other_list: list[_HasNameT],
+    /,
+) -> list[_HasNameT]:
+    '''
+    Merge lists where each item got a "name" attribute
+    '''
+    if not self_list:
+        return other_list
+    if not other_list:
+        return self_list
+
+    ret: list[_HasNameT] = []
+    other_dict = {
+        i.name: i
+        for i in other_list
+    }
+    for i in self_list:
+        if i.name in other_dict:
+            ret.append(merge(i, other_dict.pop(i.name)))
+        else:
+            ret.append(i)
+    ret.extend(other_dict.values())
+    return ret