Fix casting str type properties + add tests (#1779)

changes/1779.bugfix.rst

@@ -0,0 +1 @@
+macOS widget methods that return strings are now guaranteed to return strings, rather than native Objective C string objects.

cocoa/src/toga_cocoa/widgets/multilinetextinput.py

@@ -54,7 +54,7 @@ def create(self):
         self.add_constraints()
 
     def get_placeholder(self):
-        return self.native_text.placeholderString
+        return str(self.native_text.placeholderString)
 
     def set_placeholder(self, value):
         self.native_text.placeholderString = value
@@ -73,7 +73,7 @@ def set_readonly(self, value):
         self.native_text.editable = not value
 
     def get_value(self):
-        return self.native_text.string
+        return str(self.native_text.string)
 
     def set_value(self, value):
         self.native_text.string = value

cocoa/src/toga_cocoa/widgets/textinput.py

@@ -178,7 +178,7 @@ def set_readonly(self, value):
         self.native.selectable = True
 
     def get_placeholder(self):
-        return self.native.cell.placeholderString
+        return str(self.native.cell.placeholderString)
 
     def set_placeholder(self, value):
         self.native.cell.placeholderString = value

iOS/src/toga_iOS/widgets/multilinetextinput.py

@@ -117,7 +117,7 @@ def constrain_placeholder_label(self):
         )
 
     def get_placeholder(self):
-        return self.placeholder_label.text
+        return str(self.placeholder_label.text)
 
     def set_placeholder(self, value):
         self.placeholder_label.text = value
@@ -129,7 +129,7 @@ def set_readonly(self, value):
         self.native.editable = not value
 
     def get_value(self):
-        return self.native.text
+        return str(self.native.text)
 
     def set_value(self, value):
         self.native.text = value

testbed/tests/widgets/properties.py

@@ -108,6 +108,7 @@ async def test_text(widget, probe):
         widget.text = text
         await probe.redraw(f"Widget text should be {str(text)!r}")
 
+        assert isinstance(widget.text, str)
         assert widget.text == str(text)
         assert probe.text == str(text)
 
@@ -118,6 +119,7 @@ async def test_text_value(widget, probe):
         widget.value = text
         await probe.redraw(f"Widget value should be {str(text)!r}")
 
+        assert isinstance(widget.value, str)
         assert widget.value == str(text)
         assert probe.value == str(text)
 
@@ -129,6 +131,7 @@ async def test_placeholder(widget, probe):
     widget.value = "Hello"
     widget.placeholder = "placeholder"
     await probe.redraw("Widget placeholder should not be visible")
+    assert isinstance(widget.placeholder, str)
     assert widget.value == "Hello"
     assert widget.placeholder == "placeholder"
     assert probe.value == "Hello"

testbed/tests/widgets/test_button.py

@@ -40,6 +40,7 @@ async def test_text(widget, probe):
         await probe.redraw(f"Button text should be {text}")
 
         # Text after a newline will be stripped.
+        assert isinstance(widget.text, str)
         expected = str(text).split("\n")[0]
         assert widget.text == expected
         assert probe.text == expected

testbed/tests/widgets/test_switch.py

@@ -37,6 +37,7 @@ async def test_text(widget, probe):
 
         # Text after a newline will be stripped.
         expected = str(text).split("\n")[0]
+        assert isinstance(widget.text, str)
         assert widget.text == expected
         assert probe.text == expected
         assert probe.height == initial_height