Make ABC typings work in Python 3.7

src/ufoLib2/objects/contour.py

@@ -2,7 +2,7 @@
 
 import warnings
 from collections.abc import MutableSequence
-from typing import Iterable, Iterator, overload
+from typing import TYPE_CHECKING, Iterable, Iterator, overload
 
 from attr import define, field
 from fontTools.pens.basePen import AbstractPen
@@ -12,9 +12,15 @@
 from ufoLib2.objects.point import Point
 from ufoLib2.typing import GlyphSet
 
+# For Python 3.7 compatibility.
+if TYPE_CHECKING:
+    ContourMapping = MutableSequence[Point]
+else:
+    ContourMapping = MutableSequence
+
 
 @define
-class Contour(MutableSequence[Point]):
+class Contour(ContourMapping):
     """Represents a contour as a list of points.
 
     Behavior:

src/ufoLib2/objects/image.py

@@ -1,16 +1,22 @@
 from __future__ import annotations
 
 from collections.abc import Mapping
-from typing import Any, Iterator
+from typing import TYPE_CHECKING, Any, Iterator
 
 from attr import define, field
 from fontTools.misc.transform import Identity, Transform
 
 from .misc import _convert_transform
 
+# For Python 3.7 compatibility.
+if TYPE_CHECKING:
+    ImageMapping = Mapping[str, Any]
+else:
+    ImageMapping = Mapping
+
 
 @define
-class Image(Mapping[str, Any]):
+class Image(ImageMapping):
     """Represents a background image reference.
 
     See http://unifiedfontobject.org/versions/ufo3/images/ and

src/ufoLib2/objects/misc.py

@@ -5,7 +5,7 @@
 from abc import abstractmethod
 from collections.abc import Mapping, MutableMapping
 from copy import deepcopy
-from typing import Any, Iterator, NamedTuple, Sequence, TypeVar, cast
+from typing import TYPE_CHECKING, Any, Iterator, NamedTuple, Sequence, TypeVar, cast
 
 import attr
 from attr import define, field
@@ -115,9 +115,15 @@ class Placeholder:
 # Create a generic variable for mypy that can be 'DataStore' or any subclass.
 Tds = TypeVar("Tds", bound="DataStore")
 
+# For Python 3.7 compatibility.
+if TYPE_CHECKING:
+    DataStoreMapping = MutableMapping[str, bytes]
+else:
+    DataStoreMapping = MutableMapping
+
 
 @define
-class DataStore(MutableMapping[str, bytes]):
+class DataStore(DataStoreMapping):
     """Represents the base class for ImageSet and DataSet.
 
     Both behave like a dictionary that loads its "values" lazily by default and only
@@ -267,7 +273,14 @@ def fileNames(self) -> list[str]:
         return list(self._data.keys())
 
 
-class AttrDictMixin(Mapping[str, Any]):
+# For Python 3.7 compatibility.
+if TYPE_CHECKING:
+    AttrDictMixinMapping = Mapping[str, Any]
+else:
+    AttrDictMixinMapping = Mapping
+
+
+class AttrDictMixin(AttrDictMixinMapping):
     """Read attribute values using mapping interface.
 
     For use with Anchors and Guidelines classes, where client code