use on_setattr to auto-convert dict to Lib and Kerning

src/ufoLib2/objects/font.py

@@ -18,7 +18,7 @@
 
 import fs.base
 import fs.tempfs
-from attr import define, field
+from attr import define, field, setters
 from fontTools.ufoLib import UFOFileStructure, UFOReader, UFOWriter
 
 from ufoLib2.constants import DEFAULT_LAYER_NAME
@@ -31,7 +31,7 @@
 from ufoLib2.objects.kerning import Kerning, KerningPair
 from ufoLib2.objects.layer import Layer
 from ufoLib2.objects.layerSet import LayerSet
-from ufoLib2.objects.lib import Lib, _convert_Lib, _get_lib, _set_lib
+from ufoLib2.objects.lib import Lib, _convert_Lib
 from ufoLib2.objects.misc import (
     BoundingBox,
     _deepcopy_unlazify_attrs,
@@ -141,11 +141,13 @@ class Font:
     groups: Dict[str, List[str]] = field(factory=dict)
     """Dict[str, List[str]]: A mapping of group names to a list of glyph names."""
 
-    kerning: Kerning = field(factory=Kerning, converter=_convert_Kerning)
+    kerning: Kerning = field(
+        factory=Kerning, converter=_convert_Kerning, on_setattr=setters.convert
+    )
     """Dict[Tuple[str, str], float]: A mapping of a tuple of first and second kerning
     pair to a kerning value."""
 
-    _lib: Lib = field(factory=Lib, converter=_convert_Lib)
+    lib: Lib = field(factory=Lib, converter=_convert_Lib, on_setattr=setters.convert)
     """Dict[str, PlistEncodable]: A mapping of keys to arbitrary plist values."""
 
     data: DataSet = field(factory=DataSet, converter=_convert_DataSet)
@@ -359,8 +361,6 @@ def guidelines(self, value: Iterable[Guideline | Mapping[str, Any]]) -> None:
         for guideline in value:
             self.appendGuideline(guideline)
 
-    lib = property(_get_lib, _set_lib)
-
     def objectLib(self, object: HasIdentifier) -> dict[str, Any]:
         """Return the lib for an object with an identifier, as stored in a font's lib.
 

src/ufoLib2/objects/glyph.py

@@ -3,7 +3,7 @@
 from copy import deepcopy
 from typing import Any, Iterator, List, Mapping, Optional, cast
 
-from attr import define, field
+from attr import define, field, setters
 from fontTools.misc.transform import Transform
 from fontTools.pens.basePen import AbstractPen
 from fontTools.pens.pointPen import (
@@ -17,7 +17,7 @@
 from ufoLib2.objects.contour import Contour
 from ufoLib2.objects.guideline import Guideline
 from ufoLib2.objects.image import Image
-from ufoLib2.objects.lib import Lib, _convert_Lib, _get_lib, _set_lib
+from ufoLib2.objects.lib import Lib, _convert_Lib
 from ufoLib2.objects.misc import BoundingBox, _object_lib, getBounds, getControlBounds
 from ufoLib2.pointPens.glyphPointPen import GlyphPointPen
 from ufoLib2.typing import GlyphSet, HasIdentifier
@@ -67,7 +67,7 @@ class Glyph:
 
     _image: Image = field(factory=Image)
 
-    _lib: Lib = field(factory=Lib, converter=_convert_Lib)
+    lib: Lib = field(factory=Lib, converter=_convert_Lib, on_setattr=setters.convert)
     """The glyph's mapping of string keys to arbitrary data."""
 
     note: Optional[str] = None
@@ -102,8 +102,6 @@ def __repr__(self) -> str:
             hex(id(self)),
         )
 
-    lib = property(_get_lib, _set_lib)
-
     @property
     def anchors(self) -> list[Anchor]:
         """The list of anchors the glyph contains.

src/ufoLib2/objects/layer.py

@@ -12,12 +12,12 @@
     overload,
 )
 
-from attr import define, field
+from attr import define, field, setters
 from fontTools.ufoLib.glifLib import GlyphSet
 
 from ufoLib2.constants import DEFAULT_LAYER_NAME
 from ufoLib2.objects.glyph import Glyph
-from ufoLib2.objects.lib import Lib, _convert_Lib, _get_lib, _set_lib
+from ufoLib2.objects.lib import Lib, _convert_Lib
 from ufoLib2.objects.misc import (
     BoundingBox,
     _deepcopy_unlazify_attrs,
@@ -107,7 +107,7 @@ class Layer:
     color: Optional[str] = None
     """The color assigned to the layer."""
 
-    _lib: Lib = field(factory=Lib, converter=_convert_Lib)
+    lib: Lib = field(factory=Lib, converter=_convert_Lib, on_setattr=setters.convert)
     """The layer's lib for mapping string keys to arbitrary data."""
 
     _default: bool = False
@@ -237,8 +237,6 @@ def name(self) -> str:
         """The name of the layer."""
         return self._name
 
-    lib = property(_get_lib, _set_lib)
-
     @property
     def default(self) -> bool:
         """Read-only property. To change the font's default layer use the
@@ -387,7 +385,7 @@ def _unstructure(self, converter: GenConverter) -> dict[str, Any]:
         for key, value, default in [
             ("default", self._default, self._name == DEFAULT_LAYER_NAME),
             ("glyphs", glyphs, {}),
-            ("lib", self._lib, {}),
+            ("lib", self.lib, {}),
         ]:
             if not converter.omit_if_default or value != default:
                 d[key] = value

src/ufoLib2/objects/lib.py

@@ -26,15 +26,6 @@ def _convert_Lib(value: Mapping[str, Any]) -> Lib:
     return value if isinstance(value, Lib) else Lib(value)
 
 
-# getter/setter properties used by Font, Layer, Glyph
-def _get_lib(self: Any) -> Lib:
-    return cast(Lib, self._lib)
-
-
-def _set_lib(self: Any, value: Mapping[str, Any]) -> None:
-    self._lib = _convert_Lib(value)
-
-
 def is_data_dict(value: Any) -> bool:
     return (
         isinstance(value, Mapping)

tests/test_ufoLib2.py

@@ -2,13 +2,14 @@
 
 from copy import deepcopy
 from pathlib import Path
+from typing import Any, Type
 
 import pytest
 from fontTools import ufoLib
 
 import ufoLib2
 import ufoLib2.objects
-from ufoLib2.objects import Features, Font, Layer, LayerSet
+from ufoLib2.objects import Features, Font, Glyph, Kerning, Layer, LayerSet, Lib
 from ufoLib2.objects.layerSet import _LAYER_NOT_LOADED
 from ufoLib2.objects.misc import _DATA_NOT_LOADED
 
@@ -265,3 +266,21 @@ def test_woff_metadata(datadir: Path, tmp_path: Path) -> None:
 
 def test_features_normalize_newlines() -> None:
     assert Features("a\r\nb\rc\n").normalize_newlines().text == "a\nb\nc\n"
+
+
+@pytest.mark.parametrize(
+    "klass, attr_name, attr_type, obj",
+    [
+        (Font, "lib", Lib, {"foo": 1}),
+        (Font, "kerning", Kerning, {("a", "b"): -10}),
+        (Glyph, "lib", Lib, {"bar": [2, 3]}),
+    ],
+)
+def test_font_on_setattr(
+    klass: Type[Any], attr_name: str, attr_type: Type[Any], obj: Any
+) -> None:
+    o = klass()
+    assert isinstance(getattr(o, attr_name), attr_type)
+    assert not isinstance(obj, attr_type)
+    setattr(o, attr_name, obj)
+    assert isinstance(getattr(o, attr_name), attr_type)