Merge branch 'dev' into dependabot/pip/pip-dependencies-327d618383

Author: T4rk1n

.github/workflows/testing.yml

@@ -70,7 +70,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.8", "3.12"]
+        python-version: ["3.9", "3.12"]
 
     steps:
       - name: Checkout repository
@@ -123,7 +123,7 @@ jobs:
 
       - name: Run lint
         env:
-          PYLINT_EXTRA_ARGS: ${{ matrix.python-version == '3.8' && '--ignored-modules=mcp' || '' }}
+          PYLINT_EXTRA_ARGS: ${{ matrix.python-version == '3.9' && '--ignored-modules=mcp' || '' }}
         run: npm run lint
 
       - name: Run unit tests
@@ -615,7 +615,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.8", "3.12"]
+        python-version: ["3.9", "3.12"]
         test-group: ["1", "2", "3"]
 
     env:
@@ -719,7 +719,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.8", "3.12"]
+        python-version: ["3.9", "3.12"]
 
     env:
       PERCY_TOKEN: ${{ matrix.python-version == '3.12' && secrets.PERCY_TOKEN || '' }}
@@ -866,7 +866,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.8", "3.12"]
+        python-version: ["3.9", "3.12"]
 
     steps:
       - name: Checkout repository
@@ -914,7 +914,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.8", "3.12"]
+        python-version: ["3.9", "3.12"]
         test-group: ["1", "2", "3"]
 
     env:

CHANGELOG.md

@@ -2,6 +2,16 @@
 All notable changes to `dash` will be documented in this file.
 This project adheres to [Semantic Versioning](https://semver.org/).
 
+## [UNRELEASED]
+
+## Fixed
+- [#3822](https://github.com/plotly/dash/pull/3822) Fix `UnboundLocalError` for `user_callback_output` in async background callbacks (Celery and Diskcache managers) when the callback raises `PreventUpdate` or another exception before the variable is assigned.
+- [#3819](https://github.com/plotly/dash/pull/3819) Fix `RuntimeError: No active request in context` when a non-Dash path falls through to the FastAPI catch-all route. Fixes [#3812](https://github.com/plotly/dash/issues/3812).
+- [#3838](https://github.com/plotly/dash/pull/3838) Replace `mcp` dependency with inline types
+
+## Changed
+- Drop support for Python 3.8 (end-of-life since October 2024). The minimum supported version is now Python 3.9.
+
 ## [4.3.0] - 2026-06-18
 
 ## Added

dash/backends/_fastapi.py

@@ -334,8 +334,12 @@ def _setup_catchall(self):
         try:
             dash_app = get_app()
 
-            async def catchall(_request: Request):
-                return Response(content=dash_app.index(), media_type="text/html")
+            async def catchall(request: Request):
+                token = set_current_request(request)
+                try:
+                    return Response(content=dash_app.index(), media_type="text/html")
+                finally:
+                    reset_current_request(token)
 
             # pylint: disable=protected-access
             self.add_url_rule("{path:path}", catchall, methods=["GET"])

dash/background_callback/managers/celery_manager.py

@@ -209,6 +209,7 @@ async def async_run():
             c.updated_props = ProxySetProps(_set_props)
             context_value.set(c)
             errored = False
+            user_callback_output = None  # to help type checking
             try:
                 if isinstance(user_callback_args, dict):
                     user_callback_output = await fn(
@@ -243,10 +244,10 @@ async def async_run():
                     ),
                 )
 
-            if asyncio.iscoroutine(user_callback_output):
-                user_callback_output = await user_callback_output
-
             if not errored:
+                if asyncio.iscoroutine(user_callback_output):
+                    user_callback_output = await user_callback_output
+
                 cache.set(
                     result_key, json.dumps(user_callback_output, cls=PlotlyJSONEncoder)
                 )

dash/background_callback/managers/diskcache_manager.py

@@ -263,6 +263,7 @@ async def async_run():
             c.updated_props = ProxySetProps(_set_props)
             context_value.set(c)
             errored = False
+            user_callback_output = None  # to help type checking
             try:
                 if isinstance(user_callback_args, dict):
                     user_callback_output = await fn(
@@ -289,9 +290,9 @@ async def async_run():
                     },
                 )
 
-            if asyncio.iscoroutine(user_callback_output):
-                user_callback_output = await user_callback_output
             if not errored:
+                if asyncio.iscoroutine(user_callback_output):
+                    user_callback_output = await user_callback_output
                 try:
                     cache.set(result_key, user_callback_output)
                 except Exception as err:  # pylint: disable=broad-except

dash/mcp/_server.py

@@ -13,7 +13,7 @@
 import os
 from typing import TYPE_CHECKING, Any
 
-from mcp.types import (
+from dash.mcp.types import (
     LATEST_PROTOCOL_VERSION,
     ErrorData,
     Implementation,

dash/mcp/primitives/resources/__init__.py

@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from mcp.types import (
+from dash.mcp.types import (
     ListResourcesResult,
     ListResourceTemplatesResult,
     ReadResourceResult,

dash/mcp/primitives/resources/base.py

@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from mcp.types import ReadResourceResult, Resource, ResourceTemplate
+from dash.mcp.types import ReadResourceResult, Resource, ResourceTemplate
 
 
 class MCPResourceProvider:

dash/mcp/primitives/resources/resource_clientside_callbacks.py

@@ -5,12 +5,13 @@
 import json
 from typing import Any
 
-from mcp.types import (
+from pydantic import AnyUrl
+
+from dash.mcp.types import (
     ReadResourceResult,
     Resource,
     TextResourceContents,
 )
-from pydantic import AnyUrl
 
 from dash import get_app
 from dash._utils import clean_property_name, split_callback_id

dash/mcp/primitives/resources/resource_components.py

@@ -4,12 +4,13 @@
 
 import json
 
-from mcp.types import (
+from pydantic import AnyUrl
+
+from dash.mcp.types import (
     ReadResourceResult,
     Resource,
     TextResourceContents,
 )
-from pydantic import AnyUrl
 
 from dash import get_app
 from dash._layout_utils import traverse