Building support for decoupling Dash from Flask and supporting Quart / FastAPI servers

.github/workflows/testing.yml

@@ -17,6 +17,7 @@ jobs:
       # This output will be 'true' if files in the 'table_related_paths' list changed, 'false' otherwise.
       table_paths_changed: ${{ steps.filter.outputs.table_related_paths }}
       background_cb_changed: ${{ steps.filter.outputs.background_paths }}
+      backend_cb_changed: ${{ steps.filter.outputs.backend_paths }}
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
@@ -37,6 +38,9 @@ jobs:
               - 'tests/background_callback/**'
               - 'tests/async_tests/**'
               - 'requirements/**'
+            backend_paths:
+              - 'dash/backends/**'
+              - 'tests/backend_tests/**'
 
   build:
     name: Build Dash Package
@@ -270,6 +274,109 @@ jobs:
           cd bgtests
           pytest --headless --nopercyfinalize tests/async_tests -v -s
 
+  backend-tests:
+    name: Run Backend Callback Tests (Python ${{ matrix.python-version }})
+    needs: [build, changes_filter]
+    if: |
+      (github.event_name == 'push' && (github.ref == 'refs/heads/master' || github.ref == 'refs/heads/dev')) ||
+      needs.changes_filter.outputs.backend_cb_changed == 'true'
+    timeout-minutes: 30
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.9", "3.12"]
+
+    services:
+      redis:
+        image: redis:6
+        ports:
+          - 6379:6379
+        options: >-
+          --health-cmd "redis-cli ping"
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+
+    env:
+      REDIS_URL: redis://localhost:6379
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+
+      - name: Install Node.js dependencies
+        run: npm ci
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+          cache: 'pip'
+
+      - name: Download built Dash packages
+        uses: actions/download-artifact@v4
+        with:
+          name: dash-packages
+          path: packages/
+
+      - name: Install Dash packages
+        run: |
+          python -m pip install --upgrade pip wheel
+          python -m pip install "setuptools<78.0.0"
+          python -m pip install "selenium==4.32.0"
+          find packages -name dash-*.whl -print -exec sh -c 'pip install "{}[async,ci,testing,dev,celery,diskcache,fastapi,quart]"' \;
+
+      - name: Install Google Chrome
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y google-chrome-stable
+
+      - name: Install ChromeDriver
+        run: |
+          echo "Determining Chrome version..."
+          CHROME_BROWSER_VERSION=$(google-chrome --version)
+          echo "Installed Chrome Browser version: $CHROME_BROWSER_VERSION"
+          CHROME_MAJOR_VERSION=$(echo "$CHROME_BROWSER_VERSION" | cut -f 3 -d ' ' | cut -f 1 -d '.')
+          echo "Detected Chrome Major version: $CHROME_MAJOR_VERSION"
+          if [ "$CHROME_MAJOR_VERSION" -ge 115 ]; then
+            echo "Fetching ChromeDriver version for Chrome $CHROME_MAJOR_VERSION using CfT endpoint..."
+            CHROMEDRIVER_VERSION_STRING=$(curl -sS "https://googlechromelabs.github.io/chrome-for-testing/LATEST_RELEASE_${CHROME_MAJOR_VERSION}")
+            if [ -z "$CHROMEDRIVER_VERSION_STRING" ]; then
+              echo "Could not automatically find ChromeDriver version for Chrome $CHROME_MAJOR_VERSION via LATEST_RELEASE. Please check CfT endpoints."
+              exit 1
+            fi
+            CHROMEDRIVER_URL="https://edgedl.me.gvt1.com/edgedl/chrome/chrome-for-testing/${CHROMEDRIVER_VERSION_STRING}/linux64/chromedriver-linux64.zip"
+          else
+            echo "Fetching ChromeDriver version for Chrome $CHROME_MAJOR_VERSION using older method..."
+            CHROMEDRIVER_VERSION_STRING=$(curl -sS "https://chromedriver.storage.googleapis.com/LATEST_RELEASE_${CHROME_MAJOR_VERSION}")
+            CHROMEDRIVER_URL="https://chromedriver.storage.googleapis.com/${CHROMEDRIVER_VERSION_STRING}/chromedriver_linux64.zip"
+          fi
+          echo "Using ChromeDriver version string: $CHROMEDRIVER_VERSION_STRING"
+          echo "Downloading ChromeDriver from: $CHROMEDRIVER_URL"
+          wget -q -O chromedriver.zip "$CHROMEDRIVER_URL"
+          unzip -o chromedriver.zip -d /tmp/
+          sudo mv /tmp/chromedriver-linux64/chromedriver /usr/local/bin/chromedriver || sudo mv /tmp/chromedriver /usr/local/bin/chromedriver
+          sudo chmod +x /usr/local/bin/chromedriver
+          echo "/usr/local/bin" >> $GITHUB_PATH
+        shell: bash
+
+      - name: Build/Setup test components
+        run: npm run setup-tests.py
+
+      - name: Run Backend Callback Tests
+        run: |
+          mkdir bgtests
+          cp -r tests bgtests/tests
+          cd bgtests
+          touch __init__.py
+          pytest --headless --nopercyfinalize tests/backend_tests -v -s
+
   table-unit:
     name: Table Unit/Lint Tests (Python ${{ matrix.python-version }})
     needs: [build, changes_filter]

.gitignore

@@ -93,3 +93,4 @@ packages/
 !components/dash-core-components/tests/integration/upload/upload-assets/upft001.csv
 !components/dash-table/tests/assets/*.csv
 !components/dash-table/tests/selenium/assets/*.csv
+dash_config.json

dash/_callback.py

@@ -1,11 +1,14 @@
+from typing import Callable, Optional, Any, List, Tuple, Union
+from functools import wraps
 import collections
 import hashlib
 import inspect
+
 from functools import wraps
 
 from typing import Callable, Optional, Any, List, Tuple, Union, Dict
 
-import flask
+import asyncio
 
 from .dependencies import (
     handle_callback_args,
@@ -38,10 +41,11 @@
     clean_property_name,
 )
 
-from . import _validate
 from .background_callback.managers import BaseBackgroundCallbackManager
 from ._callback_context import context_value
 from ._no_update import NoUpdate
+from . import _validate
+from . import backends
 
 
 async def _async_invoke_callback(
@@ -375,7 +379,8 @@ def _get_callback_manager(
                 " and store results on redis.\n"
             )
 
-    old_job = flask.request.args.getlist("oldJob")
+    adapter = backends.request_adapter()
+    old_job = adapter.args.getlist("oldJob") if hasattr(adapter.args, "getlist") else []
 
     if old_job:
         for job in old_job:
@@ -389,21 +394,20 @@ def _setup_background_callback(
 ):
     """Set up the background callback and manage jobs."""
     callback_manager = _get_callback_manager(kwargs, background)
+    if not callback_manager:
+        return to_json({"error": "No background callback manager configured"})
 
     progress_outputs = background.get("progress")
 
     cache_ignore_triggered = background.get("cache_ignore_triggered", True)
 
     cache_key = callback_manager.build_cache_key(
         func,
-        # Inputs provided as dict is kwargs.
         func_args if func_args else func_kwargs,
         background.get("cache_args_to_ignore", []),
         None if cache_ignore_triggered else callback_ctx.get("triggered_inputs", []),
     )
-
     job_fn = callback_manager.func_registry.get(background_key)
-
     ctx_value = AttributeDict(**context_value.get())
     ctx_value.ignore_register_page = True
     ctx_value.pop("background_callback_manager")
@@ -435,7 +439,8 @@ def _setup_background_callback(
 
 def _progress_background_callback(response, callback_manager, background):
     progress_outputs = background.get("progress")
-    cache_key = flask.request.args.get("cacheKey")
+    adapter = backends.request_adapter()
+    cache_key = adapter.args.get("cacheKey")
 
     if progress_outputs:
         # Get the progress before the result as it would be erased after the results.
@@ -452,8 +457,9 @@ def _update_background_callback(
     """Set up the background callback and manage jobs."""
     callback_manager = _get_callback_manager(kwargs, background)
 
-    cache_key = flask.request.args.get("cacheKey")
-    job_id = flask.request.args.get("job")
+    adapter = backends.request_adapter()
+    cache_key = adapter.args.get("cacheKey") if adapter else None
+    job_id = adapter.args.get("job") if adapter else None
 
     _progress_background_callback(response, callback_manager, background)
 
@@ -473,8 +479,9 @@ def _handle_rest_background_callback(
     multi,
     has_update=False,
 ):
-    cache_key = flask.request.args.get("cacheKey")
-    job_id = flask.request.args.get("job")
+    adapter = backends.request_adapter()
+    cache_key = adapter.args.get("cacheKey") if adapter else None
+    job_id = adapter.args.get("job") if adapter else None
     # Must get job_running after get_result since get_results terminates it.
     job_running = callback_manager.job_running(job_id)
     if not job_running and output_value is callback_manager.UNDEFINED:
@@ -687,11 +694,11 @@ def add_context(*args, **kwargs):
             )
 
             response: dict = {"multi": True}  # type: ignore
-
-            jsonResponse = None
+            jsonResponse: Optional[str] = None
             try:
                 if background is not None:
-                    if not flask.request.args.get("cacheKey"):
+                    adapter = backends.request_adapter()
+                    if not (adapter and adapter.args.get("cacheKey")):
                         return _setup_background_callback(
                             kwargs,
                             background,
@@ -762,7 +769,8 @@ async def async_add_context(*args, **kwargs):
 
             try:
                 if background is not None:
-                    if not flask.request.args.get("cacheKey"):
+                    adapter = backends.request_adapter()
+                    if not (adapter and adapter.args.get("cacheKey")):
                         return _setup_background_callback(
                             kwargs,
                             background,

dash/_callback_context.py

@@ -4,9 +4,8 @@
 import contextvars
 import typing
 
-import flask
-
 from . import exceptions
+from . import backends
 from ._utils import AttributeDict, stringify_id
 
 
@@ -222,14 +221,15 @@ def record_timing(name, duration, description=None):
         :param description: A description of the resource.
         :type description: string or None
         """
-        timing_information = getattr(flask.g, "timing_information", {})
+        request = backends.backend.request_adapter()
+        timing_information = getattr(request.context, "timing_information", {})
 
         if name in timing_information:
             raise KeyError(f'Duplicate resource name "{name}" found.')
 
         timing_information[name] = {"dur": round(duration * 1000), "desc": description}
 
-        setattr(flask.g, "timing_information", timing_information)
+        setattr(request.context, "timing_information", timing_information)
 
     @property
     @has_context
@@ -252,7 +252,8 @@ def using_outputs_grouping(self):
     @property
     @has_context
     def timing_information(self):
-        return getattr(flask.g, "timing_information", {})
+        request = backends.backend.request_adapter()
+        return getattr(request.context, "timing_information", {})
 
     @has_context
     def set_props(self, component_id: typing.Union[str, dict], props: dict):
@@ -290,6 +291,14 @@ def path(self):
         """
         return _get_from_context("path", "")
 
+    @property
+    @has_context
+    def args(self):
+        """
+        Query parameters of the callback request as a dictionary-like object.
+        """
+        return _get_from_context("args", "")
+
     @property
     @has_context
     def remote(self):

dash/_configs.py

@@ -1,5 +1,5 @@
+from ._utils import get_root_path
 import os
-import flask
 
 # noinspection PyCompatibility
 from . import exceptions
@@ -127,7 +127,7 @@ def pages_folder_config(name, pages_folder, use_pages):
     if not pages_folder:
         return None
     is_custom_folder = str(pages_folder) != "pages"
-    pages_folder_path = os.path.join(flask.helpers.get_root_path(name), pages_folder)
+    pages_folder_path = os.path.join(get_root_path(name), pages_folder)
     if (use_pages or is_custom_folder) and not os.path.isdir(pages_folder_path):
         error_msg = f"""
         A folder called `{pages_folder}` does not exist. If a folder for pages is not

dash/_hooks.py

@@ -3,7 +3,6 @@
 from importlib import metadata as _importlib_metadata
 
 import typing_extensions as _tx
-import flask as _f
 
 from .exceptions import HookError
 from .resources import ResourceType
@@ -127,7 +126,7 @@ def route(
         Add a route to the Dash server.
         """
 
-        def wrap(func: _t.Callable[[], _f.Response]):
+        def wrap(func: _t.Callable[[], _t.Any]):
             _name = name or func.__name__
             self.add_hook(
                 "routes",