Use empty string as null value for FileEdit (#384)

* make fileedit use empty string as null value

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* fix typing, maybe?

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

magicgui/_type_wrapper.py

@@ -377,9 +377,7 @@ def resolve_annotation(
 
     if isinstance(annotation, str):
         if (3, 10) > sys.version_info >= (3, 9, 8) or sys.version_info >= (3, 10, 1):
-            annotation = ForwardRef(  # type: ignore
-                annotation, is_argument=False, is_class=True
-            )
+            annotation = ForwardRef(annotation, is_argument=False, is_class=True)
         else:
             annotation = ForwardRef(annotation, is_argument=False)
 

magicgui/widgets/_concrete.py

@@ -441,7 +441,10 @@ def __init__(
         nullable=False,
         **kwargs,
     ):
-        self.line_edit = LineEdit(value=kwargs.pop("value", None))
+        value = kwargs.pop("value", None)
+        if value is None:
+            value = ""
+        self.line_edit = LineEdit(value=value)
         self.choose_btn = PushButton()
         self.mode = mode  # sets the button text too
         self.filter = filter
@@ -501,8 +504,10 @@ def value(self) -> tuple[Path, ...] | Path | None:
         return Path(text)
 
     @value.setter
-    def value(self, value: Sequence[PathLike] | PathLike):
+    def value(self, value: Sequence[PathLike] | PathLike | None):
         """Set current file path."""
+        if value is None and self._nullable:
+            value = ""
         if isinstance(value, (list, tuple)):
             value = ", ".join(os.fspath(p) for p in value)
         if not isinstance(value, (str, Path)):