detect all types of null default value (#1685)

* detect all types of null default value

* fix test

* address review comments

Author: pngwn

gradio/components.py

@@ -1233,9 +1233,7 @@ def postprocess(self, y):
         Returns:
         (str): string of choice
         """
-        return (
-            y if y is not None else self.choices[0] if len(self.choices) > 0 else None
-        )
+        return y
 
     def deserialize(self, x):
         """

test/test_components.py

@@ -537,7 +537,7 @@ def test_component_functions(self):
             radio_input.get_config(),
             {
                 "choices": ["a", "b", "c"],
-                "value": "a",
+                "value": None,
                 "name": "radio",
                 "show_label": True,
                 "label": "Pick Your One Input",

ui/packages/app/src/Blocks.svelte

@@ -119,12 +119,22 @@
 		const is_input = is_dep(id, "inputs", dependencies);
 		const is_output = is_dep(id, "outputs", dependencies);
 
-		if (!is_input && !is_output && !props.value) acc.add(id); // default dynamic
+		if (!is_input && !is_output && has_no_default_value(props.value))
+			acc.add(id); // default dynamic
 		if (is_input) acc.add(id);
 
 		return acc;
 	}, new Set());
 
+	function has_no_default_value(value: any) {
+		return (
+			(Array.isArray(value) && value.length === 0) ||
+			value === "" ||
+			value === 0 ||
+			!value
+		);
+	}
+
 	let instance_map = components.reduce((acc, next) => {
 		acc[next.id] = next;
 		return acc;