avoid importing testing module

Author: rmorshea

pyproject.toml

@@ -30,9 +30,11 @@ show_missing = true
 skip_covered = true
 sort = "Name"
 exclude_lines = [
-    "pragma: no cover",
-    '\.\.\.',
-    "raise NotImplementedError",
+    # These are regex patterns
+    'pragma: no cover',
+    '...',
+    'raise NotImplementedError',
+    'if TYPE_CHECKING[\s:]',
 ]
 omit = [
     "src/idom/__main__.py",

src/idom/widgets.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from base64 import b64encode
-from typing import Any, Callable, Iterable, Tuple, TypeVar, Union
+from typing import TYPE_CHECKING, Any, Callable, Iterable, Tuple, TypeVar, Union
 
 from typing_extensions import Protocol
 
@@ -10,7 +10,6 @@
 from . import html
 from ._warnings import warn
 from .core.types import ComponentConstructor, VdomDict
-from .testing.backend import _hotswap, _MountFunc
 
 
 def image(
@@ -95,6 +94,10 @@ def __call__(self, value: str) -> _CastTo:
         ...
 
 
+if TYPE_CHECKING:
+    from .testing.backend import _MountFunc
+
+
 def hotswap(
     update_on_change: bool = False,
 ) -> Tuple[_MountFunc, ComponentConstructor]:  # pragma: no cover
@@ -103,4 +106,6 @@ def hotswap(
         DeprecationWarning,
         stacklevel=2,
     )
+    from .testing.backend import _hotswap
+
     return _hotswap(update_on_change)