Use updated component in postprocess() (#7402)

* component update

* add changeset

* add test

* lint

* refactor

---------

Co-authored-by: gradio-pr-bot <gradio-pr-bot@users.noreply.github.com>

.changeset/blue-walls-flash.md

@@ -0,0 +1,5 @@
+---
+"gradio": patch
+---
+
+fix:Use updated component in `postprocess()`

gradio/blocks.py

@@ -1449,7 +1449,10 @@ def postprocess_data(
                         raise InvalidComponentError(
                             f"{block.__class__} Component with id {output_id} not a valid output component."
                         )
+                    if output_id in state:
+                        block = state[output_id]
                     prediction_value = block.postprocess(prediction_value)
+
                 outputs_cached = processing_utils.move_files_to_cache(
                     prediction_value,
                     block,  # type: ignore

test/test_blocks.py

@@ -18,7 +18,7 @@
 import pytest
 import uvicorn
 from fastapi.testclient import TestClient
-from gradio_client import media_data
+from gradio_client import Client, media_data
 from PIL import Image
 
 import gradio as gr
@@ -823,6 +823,26 @@ def run(min, num):
             "error" not in session_1.json()
         )  # no error because sesssion 1 block config was lost when session 3 was added
 
+    def test_state_holder_is_used_in_postprocess(self, connect):
+        with gr.Blocks() as demo:
+            dropdown = gr.Dropdown(label="list", choices=["Choice 1"], interactive=True)
+            button = gr.Button("Get dropdown value")
+            button2 = gr.Button("Convert dropdown to multiselect")
+            button.click(
+                lambda x: x, inputs=dropdown, outputs=dropdown, api_name="predict"
+            )
+            button2.click(
+                lambda: gr.Dropdown(multiselect=True),
+                outputs=dropdown,
+                api_name="set_multiselect",
+            )
+
+        client: Client
+        with connect(demo) as client:
+            assert client.predict("Choice 1", api_name="/predict") == "Choice 1"
+            client.predict(api_name="/set_multiselect")
+            assert client.predict("Choice 1", api_name="/predict") == ["Choice 1"]
+
 
 class TestCallFunction:
     @pytest.mark.asyncio