Merge pull request #2625 from plotly/fix/#2624

Fix background callbacks missing cancel error.

Author: T4rk1n

Diff for: CHANGELOG.md

@@ -3,6 +3,12 @@ All notable changes to `dash` will be documented in this file.
 This project adheres to [Semantic Versioning](https://semver.org/).
 
 
+## [2.12.1] - 2023-08-16
+
+## Fixed
+
+- [#2625](https://github.com/plotly/dash/pull/2625) Fix background callbacks without cancel arguments failing setup, fix [#2624](https://github.com/plotly/dash/issues/2624)
+
 ## [2.12.0] - 2023-08-14
 
 ## Fixed

Diff for: dash/dash.py

@@ -1321,8 +1321,8 @@ def _setup_server(self):
             long = callback.get("long")
             if not long:
                 continue
-            cancel = long.pop("cancel_inputs")
-            if cancel:
+            if "cancel_inputs" in long:
+                cancel = long.pop("cancel_inputs")
                 for c in cancel:
                     cancels[c] = long.get("manager")
 

Diff for: dash/version.py

@@ -1 +1 @@
-__version__ = "2.12.0"
+__version__ = "2.12.1"

Diff for: tests/integration/long_callback/app_page_cancel.py

@@ -34,6 +34,8 @@
             html.Button("cancel1", id="cancel1"),
             html.Div("idle", id="progress1"),
             html.Div("initial", id="output1"),
+            html.Div("no-cancel-btn", id="no-cancel-btn"),
+            html.Div("no-cancel", id="no-cancel-output"),
         ]
     ),
 )
@@ -51,6 +53,16 @@
 )
 
 
+@app.callback(
+    Output("no-cancel-output", "children"),
+    Input("no-cancel-btn", "n_clicks"),
+    background=True,
+    prevent_initial_call=True,
+)
+def on_click_no_cancel(_):
+    return "Not Canceled"
+
+
 @app.callback(
     Output("output1", "children"),
     Input("start1", "n_clicks"),