Wrap value in list for CheckBoxGroup.

CHANGELOG.md

@@ -25,6 +25,7 @@ By [@freddyaboulton](https://github.com/freddyaboulton) in [PR 2807](https://git
 ## Bug Fixes:
 * Fixes loading Spaces that have components with default values by [@abidlabs](https://github.com/abidlabs) in [PR 2855](https://github.com/gradio-app/gradio/pull/2855) 
 * Fixes flagging when `allow_flagging="auto"` in `gr.Interface()` by [@abidlabs](https://github.com/abidlabs) in [PR 2695](https://github.com/gradio-app/gradio/pull/2695)
+* Fixed bug where passing a non-list value to `gr.CheckboxGroup` would crash the entire app by [@freddyaboulton](https://github.com/freddyaboulton) in [PR 2866](https://github.com/gradio-app/gradio/pull/2866) 
 
 ## Documentation Changes:
 * Added a Guide on using BigQuery with Gradio's `DataFrame` and `ScatterPlot` component,

gradio/components.py

@@ -952,7 +952,7 @@ def get_config(self):
 
     @staticmethod
     def update(
-        value: Optional[List[str]] = _Keywords.NO_VALUE,
+        value: Optional[List[str] | str] = _Keywords.NO_VALUE,
         choices: Optional[List[str]] = None,
         label: Optional[str] = None,
         show_label: Optional[bool] = None,
@@ -991,15 +991,19 @@ def preprocess(self, x: List[str]) -> List[str] | List[int]:
                 + ". Please choose from: 'value', 'index'."
             )
 
-    def postprocess(self, y: List[str] | None) -> List[str]:
+    def postprocess(self, y: List[str] | str | None) -> List[str]:
         """
         Any postprocessing needed to be performed on function output.
         Parameters:
             y: List of selected choices
         Returns:
             List of selected choices
         """
-        return [] if y is None else y
+        if y is None:
+            return []
+        if not isinstance(y, list):
+            y = [y]
+        return y
 
     def set_interpret_parameters(self):
         """

test/test_components.py

@@ -493,6 +493,10 @@ def test_component_functions(self):
         with pytest.raises(ValueError):
             gr.CheckboxGroup(["a"], type="unknown")
 
+        cbox = gr.CheckboxGroup(choices=["a", "b"], value="c")
+        assert cbox.get_config()["value"] == ["c"]
+        assert cbox.postprocess("a") == ["a"]
+
     def test_in_interface(self):
         """
         Interface, process