Return empty tuple for no selected files (#415)

* Return empty tuple for no selected files

This change makes the FileEdit in EXISTING_FILES mode return an empty tuple if no files are selected.

The ability to detect "no selected file" is important to prevent parsing files that don't exist. The FileEdit has three possibilities, either it always has a Path value, or it is nullable and the neutral value should be None, or it is in multiple file selection mode and according to the signature, the neutral element should be an empty tuple.

However, since `""`.split(some_delimiter)` always gives `[""]`, it currently returns a tuple with an empty path `Path(".")` which equals the home directory and is very impractical to distinguish from an intentionally selected path.

* Check each individual split path for emptyness

* Add test case for FileEdit value

* Fix path expansion for no path and multiple paths

Author: aeisenbarth

magicgui/widgets/_concrete.py

@@ -502,21 +502,23 @@ def value(self) -> tuple[Path, ...] | Path | None:
         if self._nullable and not text:
             return None
         if self.mode is FileDialogMode.EXISTING_FILES:
-            return tuple(Path(p) for p in text.split(", "))
+            return tuple(Path(p) for p in text.split(", ") if p.strip())
         return Path(text)
 
     @value.setter
     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)):
+        elif isinstance(value, (list, tuple)):
+            value = ", ".join(os.fspath(Path(p).expanduser().absolute()) for p in value)
+        elif isinstance(value, (str, Path)):
+            value = os.fspath(Path(value).expanduser().absolute())
+        else:
             raise TypeError(
                 f"value must be a string, or list/tuple of strings, got {type(value)}"
             )
-        self.line_edit.value = os.fspath(Path(value).expanduser().absolute())
+        self.line_edit.value = value
 
     def __repr__(self) -> str:
         """Return string representation."""

tests/test_widgets.py

@@ -7,7 +7,7 @@
 import pytest
 from tests import MyInt
 
-from magicgui import magicgui, use_app, widgets
+from magicgui import magicgui, types, use_app, widgets
 from magicgui.widgets._bases import ValueWidget
 
 
@@ -629,6 +629,37 @@ def test_file_dialog_button_events():
     assert fe.value == Path("hi")
 
 
+def test_file_edit_values():
+    cwd = Path(".").absolute()
+
+    fe = widgets.FileEdit(mode=types.FileDialogMode.EXISTING_FILE)
+    assert isinstance(fe.value, Path)
+
+    fe.value = Path("hi")
+    assert fe.value == cwd / "hi"
+
+    fe = widgets.FileEdit(mode=types.FileDialogMode.EXISTING_FILE, nullable=True)
+    assert fe.value is None
+
+    fe.value = Path("hi")
+    assert fe.value == cwd / "hi"
+
+    fe.value = None
+    assert fe.value is None
+
+    fe = widgets.FileEdit(mode=types.FileDialogMode.EXISTING_FILES)
+    assert fe.value == tuple()
+
+    fe.value = Path("hi")
+    assert fe.value == (cwd / "hi",)
+
+    fe.value = (Path("hi"), Path("world"))
+    assert fe.value == (cwd / "hi", cwd / "world")
+
+    fe.value = tuple()
+    assert fe.value == tuple()
+
+
 def test_null_events():
     """Test that nullable widgets emit events when their null value is set"""
     wdg = widgets.ComboBox(choices=["a", "b"], nullable=True)