Fix background callbacks & register page

CHANGELOG.md

@@ -12,6 +12,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 - [#2152](https://github.com/plotly/dash/pull/2152) Fix bug [#2128](https://github.com/plotly/dash/issues/2128) preventing rendering of multiple components inside a dictionary.
 - [#2187](https://github.com/plotly/dash/pull/2187) Fix confusing error message when trying to use pytest fixtures but `dash[testing]` is not installed.
 - [#2202](https://github.com/plotly/dash/pull/2202) Fix bug [#2185](https://github.com/plotly/dash/issues/2185) when you copy text with multiple quotes into a table
+- [#2226](https://github.com/plotly/dash/pull/2226) Fix [#2219](https://github.com/plotly/dash/issues/2219) pages register & background callbacks.
 
 ## [2.6.1] - 2022-08-01
 

dash/_callback.py

@@ -374,6 +374,7 @@ def add_context(*args, **kwargs):
  input_values=callback_ctx.input_values,
  state_values=callback_ctx.state_values,
  triggered_inputs=callback_ctx.triggered_inputs,
+ ignore_register_page=True,
  ),
  )
 

dash/_pages.py

@@ -9,6 +9,7 @@
 from . import _validate
 from ._utils import AttributeDict
 from ._get_paths import get_relative_path
+from ._callback_context import context_value
 
 
 CONFIG = AttributeDict()
@@ -250,6 +251,9 @@ def register_page(
  ])
  ```
  """
+ if context_value.get().get("ignore_register_page"):
+ return
+
  _validate.validate_use_pages(CONFIG)
 
  page = dict(

dash/_validate.py

@@ -8,6 +8,7 @@
 from .development.base_component import Component
 from . import exceptions
 from ._utils import patch_collections_abc, stringify_id, to_json, coerce_to_list
+from .exceptions import PageError
 
 
 def validate_callback(outputs, inputs, state, extra_args, types):
@@ -462,10 +463,10 @@ def validate_pages_layout(module, page):
 
 def validate_use_pages(config):
  if not config.get("assets_folder", None):
- raise Exception("`dash.register_page()` must be called after app instantiation")
+ raise PageError("`dash.register_page()` must be called after app instantiation")
 
  if flask.has_request_context():
- raise Exception(
+ raise PageError(
  """
  dash.register_page() can’t be called within a callback as it updates dash.page_registry, which is a global variable.
  For more details, see https://dash.plotly.com/sharing-data-between-callbacks#why-global-variables-will-break-your-app

dash/dash.py

@@ -1208,6 +1208,8 @@ def dispatch(self):
  cb = self.callback_map[output]
  func = cb["callback"]
 
+ g.ignore_register_page = cb.get("long", False)
+
  # Add args_grouping
  inputs_state_indices = cb["inputs_state_indices"]
  inputs_state = inputs + state

dash/exceptions.py

@@ -93,3 +93,7 @@ class LongCallbackError(DashException):
 
 class MissingLongCallbackManagerError(DashException):
  pass
+
+
+class PageError(DashException):
+ pass

dash/long_callback/managers/celery_manager.py

@@ -147,7 +147,9 @@ def _set_progress(progress_value):
  ctx = copy_context()
 
  def run():
- context_value.set(AttributeDict(**context))
+ c = AttributeDict(**context)
+ c.ignore_register_page = False
+ context_value.set(c)
  try:
  if isinstance(user_callback_args, dict):
  user_callback_output = fn(*maybe_progress, **user_callback_args)

dash/long_callback/managers/diskcache_manager.py

@@ -1,6 +1,9 @@
 import traceback
+from contextvars import copy_context
 
 from . import BaseLongCallbackManager
+from ..._callback_context import context_value
+from ..._utils import AttributeDict
 from ...exceptions import PreventUpdate
 
 _pending_value = "__$pending__"
@@ -110,12 +113,13 @@ def make_job_fn(self, fn, progress):
  def clear_cache_entry(self, key):
  self.handle.delete(key)
 
+ # noinspection PyUnresolvedReferences
  def call_job_fn(self, key, job_fn, args, context):
  # pylint: disable-next=import-outside-toplevel,no-name-in-module,import-error
  from multiprocess import Process
 
  # pylint: disable-next=not-callable
- proc = Process(target=job_fn, args=(key, self._make_progress_key(key), args))
+ proc = Process(target=job_fn, args=(key, self._make_progress_key(key), args, context))
  proc.start()
  return proc.pid
 
@@ -147,7 +151,7 @@ def get_result(self, key, job):
 
 
 def _make_job_fn(fn, cache, progress):
- def job_fn(result_key, progress_key, user_callback_args):
+ def job_fn(result_key, progress_key, user_callback_args, context):
  def _set_progress(progress_value):
  if not isinstance(progress_value, (list, tuple)):
  progress_value = [progress_value]
@@ -156,27 +160,35 @@ def _set_progress(progress_value):
 
  maybe_progress = [_set_progress] if progress else []
 
- try:
- if isinstance(user_callback_args, dict):
- user_callback_output = fn(*maybe_progress, **user_callback_args)
- elif isinstance(user_callback_args, (list, tuple)):
- user_callback_output = fn(*maybe_progress, *user_callback_args)
+ ctx = copy_context()
+
+ def run():
+ c = AttributeDict(**context)
+ c.ignore_register_page = False
+ context_value.set(c)
+ try:
+ if isinstance(user_callback_args, dict):
+ user_callback_output = fn(*maybe_progress, **user_callback_args)
+ elif isinstance(user_callback_args, (list, tuple)):
+ user_callback_output = fn(*maybe_progress, *user_callback_args)
+ else:
+ user_callback_output = fn(*maybe_progress, user_callback_args)
+ except PreventUpdate:
+ cache.set(result_key, {"_dash_no_update": "_dash_no_update"})
+ except Exception as err: # pylint: disable=broad-except
+ cache.set(
+ result_key,
+ {
+ "long_callback_error": {
+ "msg": str(err),
+ "tb": traceback.format_exc(),
+ }
+ },
+ )
  else:
- user_callback_output = fn(*maybe_progress, user_callback_args)
- except PreventUpdate:
- cache.set(result_key, {"_dash_no_update": "_dash_no_update"})
- except Exception as err: # pylint: disable=broad-except
- cache.set(
- result_key,
- {
- "long_callback_error": {
- "msg": str(err),
- "tb": traceback.format_exc(),
- }
- },
- )
- else:
- cache.set(result_key, user_callback_output)
+ cache.set(result_key, user_callback_output)
+
+ ctx.run(run)
 
  return job_fn
 

dash/testing/__init__.py

@@ -0,0 +1,17 @@
+from contextlib import contextmanager
+
+from .._callback_context import context_value as _ctx
+from .._utils import AttributeDict as _AD
+
+
+@contextmanager
+def ignore_register_page():
+ previous = _ctx.get()
+ copied = _AD(previous)
+ copied.ignore_register_page = True
+ _ctx.set(copied)
+
+ try:
+ yield
+ finally:
+ _ctx.set(previous)

tests/unit/test_testing.py

@@ -0,0 +1,7 @@
+from dash.testing import ignore_register_page
+from dash import register_page
+
+
+def test_tst001_ignore_register_page():
+ with ignore_register_page():
+ register_page("/")