This document describes the current stable version of Celery (5.6). For development docs, go here.

# Source code for celery.result

    """Task results/state and results for groups of tasks."""

    import datetime
    import time
    from collections import deque
    from contextlib import contextmanager
    from weakref import proxy

    from dateutil.parser import isoparse
    from kombu.utils.objects import cached_property
    from vine import Thenable, barrier, promise

    from . import current_app, states
    from ._state import _set_task_join_will_block, task_join_will_block
    from .app import app_or_default
    from .exceptions import ImproperlyConfigured, IncompleteStream, TimeoutError
    from .utils.graph import DependencyGraph, GraphFormatter

    try:
        import tblib
    except ImportError:
        tblib = None

    __all__ = (
        'ResultBase', 'AsyncResult', 'ResultSet',
        'GroupResult', 'EagerResult', 'result_from_tuple',
    )

    E_WOULDBLOCK = """\
    Never call result.get() within a task!
    See https://docs.celeryq.dev/en/latest/userguide/tasks.html\
    #avoid-launching-synchronous-subtasks
    """

    def assert_will_not_block():
        if task_join_will_block():
            raise RuntimeError(E_WOULDBLOCK)

    @contextmanager
    def allow_join_result():
        reset_value = task_join_will_block()
        _set_task_join_will_block(False)
        try:
            yield
        finally:
            _set_task_join_will_block(reset_value)

    @contextmanager
    def denied_join_result():
        reset_value = task_join_will_block()
        _set_task_join_will_block(True)
        try:
            yield
        finally:
            _set_task_join_will_block(reset_value)

    class ResultBase:
        """Base class for results."""

        #: Parent result (if part of a chain)
        parent = None

    @Thenable.register
    class AsyncResult(ResultBase):
        """Query task state.

        Arguments:
            id (str): See :attr:`id`.
            backend (Backend): See :attr:`backend`.
        """

        app = None

        #: Error raised for timeouts.
        TimeoutError = TimeoutError

        #: The task's UUID.
        id = None

        #: The task result backend to use.
        backend = None

        def __init__(self, id, backend=None,
                     task_name=None,            # deprecated
                     app=None, parent=None):
            if id is None:
                raise ValueError(
                    f'AsyncResult requires valid id, not {type(id)}')
            self.app = app_or_default(app or self.app)
            self.id = id
            self.backend = backend or self.app.backend
            self.parent = parent
            self.on_ready = promise(self._on_fulfilled, weak=True)
            self._cache = None
            self._ignored = False

        @property
        def ignored(self):
            """If True, task result retrieval is disabled."""
            if hasattr(self, '_ignored'):
                return self._ignored
            return False

        @ignored.setter
        def ignored(self, value):
            """Enable/disable task result retrieval."""
            self._ignored = value

        def then(self, callback, on_error=None, weak=False):
            self.backend.add_pending_result(self, weak=weak)
            return self.on_ready.then(callback, on_error)

        def _on_fulfilled(self, result):
            self.backend.remove_pending_result(self)
            return result

        def as_tuple(self):
            parent = self.parent
            return (self.id, parent and parent.as_tuple()), None

        def as_list(self):
            """Return as a list of task IDs."""
            results = []
            parent = self.parent
            results.append(self.id)
            if parent is not None:
                results.extend(parent.as_list())
            return results

        def forget(self):
            """Forget the result of this task and its parents."""
            self._cache = None
            if self.parent:
                self.parent.forget()

            self.backend.remove_pending_result(self)
            self.backend.forget(self.id)

        def revoke(self, connection=None, terminate=False, signal=None,
                   wait=False, timeout=None):
            """Send revoke signal to all workers.

            Any worker receiving the task, or having reserved the
            task, *must* ignore it.

            Arguments:
                terminate (bool): Also terminate the process currently working
                    on the task (if any).
                signal (str): Name of signal to send to process if terminate.
                    Default is TERM.
                wait (bool): Wait for replies from workers.
                    The ``timeout`` argument specifies the seconds to wait.
                    Disabled by default.
                timeout (float): Time in seconds to wait for replies when
                    ``wait`` is enabled.
            """
            self.app.control.revoke(self.id, connection=connection,
                                    terminate=terminate, signal=signal,
                                    reply=wait, timeout=timeout)

        def revoke_by_stamped_headers(self, headers, connection=None, terminate=False, signal=None,
                                      wait=False, timeout=None):
            """Send revoke signal to all workers only for tasks with matching headers values.

            Any worker receiving the task, or having reserved the
            task, *must* ignore it.
            All header fields *must* match.

            Arguments:
                headers (dict[str, Union(str, list)]): Headers to match when revoking tasks.
                terminate (bool): Also terminate the process currently working
                    on the task (if any).
                signal (str): Name of signal to send to process if terminate.
                    Default is TERM.
                wait (bool): Wait for replies from workers.
                    The ``timeout`` argument specifies the seconds to wait.
                    Disabled by default.
                timeout (float): Time in seconds to wait for replies when
                    ``wait`` is enabled.
            """
            self.app.control.revoke_by_stamped_headers(headers, connection=connection,
                                                       terminate=terminate, signal=signal,
                                                       reply=wait, timeout=timeout)

        def get(self, timeout=None, propagate=True, interval=0.5,
                no_ack=True, follow_parents=True, callback=None, on_message=None,
                on_interval=None, disable_sync_subtasks=True,
                EXCEPTION_STATES=states.EXCEPTION_STATES,
                PROPAGATE_STATES=states.PROPAGATE_STATES):
            """Wait until task is ready, and return its result.

            Warning:
               Waiting for tasks within a task may lead to deadlocks.
               Please read :ref:`task-synchronous-subtasks`.

            Warning:
               Backends use resources to store and transmit results. To ensure
               that resources are released, you must eventually call
               :meth:`~@AsyncResult.get` or :meth:`~@AsyncResult.forget` on
               EVERY :class:`~@AsyncResult` instance returned after calling
               a task.

            Arguments:
                timeout (float): How long to wait, in seconds, before the
                    operation times out. This is the setting for the publisher
                    (celery client) and is different from `timeout` parameter of
                    `@app.task`, which is the setting for the worker. The task
                    isn't terminated even if timeout occurs.
                propagate (bool): Re-raise exception if the task failed.
                interval (float): Time to wait (in seconds) before retrying to
                    retrieve the result.  Note that this does not have any effect
                    when using the RPC/redis result store backends, as they don't
                    use polling.
                no_ack (bool): Enable amqp no ack (automatically acknowledge
                    message).  If this is :const:`False` then the message will
                    **not be acked**.
                follow_parents (bool): Re-raise any exception raised by
                    parent tasks.
                disable_sync_subtasks (bool): Disable tasks to wait for sub tasks
                    this is the default configuration. CAUTION do not enable this
                    unless you must.

            Raises:
                celery.exceptions.TimeoutError: if `timeout` isn't
                    :const:`None` and the result does not arrive within
                    `timeout` seconds.
                Exception: If the remote call raised an exception then that
                    exception will be re-raised in the caller process.
            """
            if self.ignored:
                return

            if disable_sync_subtasks:
                assert_will_not_block()
            _on_interval = promise()
            if follow_parents and propagate and self.parent:
                _on_interval = promise(self._maybe_reraise_parent_error, weak=True)
                self._maybe_reraise_parent_error()
            if on_interval:
                _on_interval.then(on_interval)

            if self._cache:
                if propagate:
                    self.maybe_throw(callback=callback)
                return self.result

            self.backend.add_pending_result(self)
            return self.backend.wait_for_pending(
                self, timeout=timeout,
                interval=interval,
                on_interval=_on_interval,
                no_ack=no_ack,
                propagate=propagate,
                callback=callback,
                on_message=on_message,
            )

        wait = get  # deprecated alias to :meth:`get`.

        def _maybe_reraise_parent_error(self):
            for node in reversed(list(self._parents())):
                node.maybe_throw()

        def _parents(self):
            node = self.parent
            while node:
                yield node
                node = node.parent

        def collect(self, intermediate=False, **kwargs):
            """Collect results as they return.

            Iterator, like :meth:`get` will wait for the task to complete,
            but will also follow :class:`AsyncResult` and :class:`ResultSet`
            returned by the task, yielding ``(result, value)`` tuples for each
            result in the tree.

            An example would be having the following tasks:

            .. code-block:: python

                from celery import group
                from proj.celery import app

                @app.task(trail=True)
                def A(how_many):
                    return group(B.s(i) for i in range(how_many))()

                @app.task(trail=True)
                def B(i):
                    return pow2.delay(i)

                @app.task(trail=True)
                def pow2(i):
                    return i ** 2

            .. code-block:: pycon

                >>> from celery.result import ResultBase
                >>> from proj.tasks import A

                >>> result = A.delay(10)
                >>> [v for v in result.collect()
                ...  if not isinstance(v, (ResultBase, tuple))]
                [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

            Note:
                The ``Task.trail`` option must be enabled
                so that the list of children is stored in ``result.children``.
                This is the default but enabled explicitly for illustration.

            Yields:
                Tuple[AsyncResult, Any]: tuples containing the result instance
                of the child task, and the return value of that task.
            """
            for _, R in self.iterdeps(intermediate=intermediate):
                yield R, R.get(**kwargs)

        def get_leaf(self):
            value = None
            for _, R in self.iterdeps():
                value = R.get()
            return value

        def iterdeps(self, intermediate=False):
            stack = deque([(None, self)])

            is_incomplete_stream = not intermediate

            while stack:
                parent, node = stack.popleft()
                yield parent, node
                if node.ready():
                    stack.extend((node, child) for child in node.children or [])
                else:
                    if is_incomplete_stream:
                        raise IncompleteStream()

        def ready(self):
            """Return :const:`True` if the task has executed.

            If the task is still running, pending, or is waiting
            for retry then :const:`False` is returned.
            """
            return self.state in self.backend.READY_STATES

        def successful(self):
            """Return :const:`True` if the task executed successfully."""
            return self.state == states.SUCCESS

        def failed(self):
            """Return :const:`True` if the task failed."""
            return self.state == states.FAILURE

        def throw(self, *args, **kwargs):
            self.on_ready.throw(*args, **kwargs)

        def maybe_throw(self, propagate=True, callback=None):
            cache = self._get_task_meta() if self._cache is None else self._cache
            state, value, tb = (
                cache['status'], cache['result'], cache.get('traceback'))
            if state in states.PROPAGATE_STATES and propagate:
                self.throw(value, self._to_remote_traceback(tb))
            if callback is not None:
                callback(self.id, value)
            return value

        maybe_reraise = maybe_throw   # XXX compat alias

        def _to_remote_traceback(self, tb):
            if tb and tblib is not None and self.app.conf.task_remote_tracebacks:
                return tblib.Traceback.from_string(tb).as_traceback()

        def build_graph(self, intermediate=False, formatter=None):
            graph = DependencyGraph(
                formatter=formatter or GraphFormatter(root=self.id, shape='oval'),
            )
            for parent, node in self.iterdeps(intermediate=intermediate):
                graph.add_arc(node)
                if parent:
                    graph.add_edge(parent, node)
            return graph

        def __str__(self):
            """`str(self) -> self.id`."""
            return str(self.id)

        def __hash__(self):
            """`hash(self) -> hash(self.id)`."""
            return hash(self.id)

        def __repr__(self):
            return f'<{type(self).__name__}: {self.id}>'

        def __eq__(self, other):
            if isinstance(other, AsyncResult):
                return other.id == self.id
            elif isinstance(other, str):
                return other == self.id
            return NotImplemented

        def __copy__(self):
            return self.__class__(
                self.id, self.backend, None, self.app, self.parent,
            )

        def __reduce__(self):
            return self.__class__, self.__reduce_args__()

        def __reduce_args__(self):
            return self.id, self.backend, None, None, self.parent

        def __del__(self):
            """Cancel pending operations when the instance is destroyed."""
            if self.backend is not None:
                self.backend.remove_pending_result(self)

        @cached_property
        def graph(self):
            return self.build_graph()

        @property
        def supports_native_join(self):
            return self.backend.supports_native_join

        @property
        def children(self):
            return self._get_task_meta().get('children')

        def _maybe_set_cache(self, meta):
            if meta:
                state = meta['status']
                if state in states.READY_STATES:
                    d = self._set_cache(self.backend.meta_from_decoded(meta))
                    self.on_ready(self)
                    return d
            return meta

        def _get_task_meta(self):
            if self._cache is None:
                return self._maybe_set_cache(self.backend.get_task_meta(self.id))
            return self._cache

        def _iter_meta(self, **kwargs):
            return iter([self._get_task_meta()])

        def _set_cache(self, d):
            children = d.get('children')
            if children:
                d['children'] = [
                    result_from_tuple(child, self.app) for child in children
                ]
            self._cache = d
            return d

        @property
        def result(self):
            """Task return value.

            Note:
                When the task has been executed, this contains the return value.
                If the task raised an exception, this will be the exception
                instance.
            """
            return self._get_task_meta()['result']
        info = result

        @property
        def traceback(self):
            """Get the traceback of a failed task."""
            return self._get_task_meta().get('traceback')

        @property
        def state(self):
            """The tasks current state.

            Possible values includes:

                *PENDING*

                    The task is waiting for execution.

                *STARTED*

                    The task has been started.

                *RETRY*

                    The task is to be retried, possibly because of failure.

                *FAILURE*

                    The task raised an exception, or has exceeded the retry limit.
                    The :attr:`result` attribute then contains the
                    exception raised by the task.

                *SUCCESS*

                    The task executed successfully.  The :attr:`result` attribute
                    then contains the tasks return value.
            """
            return self._get_task_meta()['status']
        status = state  # XXX compat

        @property
        def task_id(self):
            """Compat. alias to :attr:`id`."""
            return self.id

        @task_id.setter
        def task_id(self, id):
            self.id = id

        @property
        def name(self):
            return self._get_task_meta().get('name')

        @property
        def args(self):
            return self._get_task_meta().get('args')

        @property
        def kwargs(self):
            return self._get_task_meta().get('kwargs')

        @property
        def worker(self):
            return self._get_task_meta().get('worker')

        @property
        def date_done(self):
            """UTC date and time."""
            date_done = self._get_task_meta().get('date_done')
            if date_done and not isinstance(date_done, datetime.datetime):
                return isoparse(date_done)
            return date_done

        @property
        def retries(self):
            return self._get_task_meta().get('retries')

        @property
        def queue(self):
            return self._get_task_meta().get('queue')

    @Thenable.register
    class ResultSet(ResultBase):
        """A collection of results.

        Arguments:
            results (Sequence[AsyncResult]): List of result instances.
        """

        _app = None

        #: List of results in in the set.
        results = None

        def __init__(self, results, app=None, ready_barrier=None, **kwargs):
            self._app = app
            self.results = results
            self.on_ready = promise(args=(proxy(self),))
            self._on_full = ready_barrier or barrier(results)
            if self._on_full:
                self._on_full.then(promise(self._on_ready, weak=True))

        def add(self, result):
            """Add :class:`AsyncResult` as a new member of the set.

            Does nothing if the result is already a member.
            """
            if result not in self.results:
                self.results.append(result)
                if self._on_full:
                    self._on_full.add(result)

        def _on_ready(self):
            if self.backend.is_async:
                self.on_ready()

        def remove(self, result):
            """Remove result from the set; it must be a member.

            Raises:
                KeyError: if the result isn't a member.
            """
            if isinstance(result, str):
                result = self.app.AsyncResult(result)
            try:
                self.results.remove(result)
            except ValueError:
                raise KeyError(result)

        def discard(self, result):
            """Remove result from the set if it is a member.

            Does nothing if it's not a member.
            """
            try:
                self.remove(result)
            except KeyError:
                pass

        def update(self, results):
            """Extend from iterable of results."""
            self.results.extend(r for r in results if r not in self.results)

        def clear(self):
            """Remove all results from this set."""
            self.results[:] = []  # don't create new list.

        def successful(self):
            """Return true if all tasks successful.

            Returns:
                bool: true if all of the tasks finished
                    successfully (i.e. didn't raise an exception).
            """
            return all(result.successful() for result in self.results)

        def failed(self):
            """Return true if any of the tasks failed.

            Returns:
                bool: true if one of the tasks failed.
                    (i.e., raised an exception)
            """
            return any(result.failed() for result in self.results)

        def maybe_throw(self, callback=None, propagate=True):
            for result in self.results:
                result.maybe_throw(callback=callback, propagate=propagate)

        maybe_reraise = maybe_throw  # XXX compat alias.

        def waiting(self):
            """Return true if any of the tasks are incomplete.

            Returns:
                bool: true if one of the tasks are still
                    waiting for execution.
            """
            return any(not result.ready() for result in self.results)

        def ready(self):
            """Did all of the tasks complete? (either by success of failure).

            Returns:
                bool: true if all of the tasks have been executed.
            """
            return all(result.ready() for result in self.results)

        def completed_count(self):
            """Task completion count.

            Note that `complete` means `successful` in this context. In other words, the
            return value of this method is the number of ``successful`` tasks.

            Returns:
                int: the number of complete (i.e. successful) tasks.
            """
            return sum(int(result.successful()) for result in self.results)

        def forget(self):
            """Forget about (and possible remove the result of) all the tasks."""
            for result in self.results:
                result.forget()

        def revoke(self, connection=None, terminate=False, signal=None,
                   wait=False, timeout=None):
            """Send revoke signal to all workers for all tasks in the set.

            Arguments:
                terminate (bool): Also terminate the process currently working
                    on the task (if any).
                signal (str): Name of signal to send to process if terminate.
                    Default is TERM.
                wait (bool): Wait for replies from worker.
                    The ``timeout`` argument specifies the number of seconds
                    to wait.  Disabled by default.
                timeout (float): Time in seconds to wait for replies when
                    the ``wait`` argument is enabled.
            """
            self.app.control.revoke([r.id for r in self.results],
                                    connection=connection, timeout=timeout,
                                    terminate=terminate, signal=signal, reply=wait)

        def __iter__(self):
            return iter(self.results)

        def __getitem__(self, index):
            """`res[i] -> res.results[i]`."""
            return self.results[index]

        def get(self, timeout=None, propagate=True, interval=0.5,
                callback=None, no_ack=True, on_message=None,
                disable_sync_subtasks=True, on_interval=None):
            """See :meth:`join`.

            This is here for API compatibility with :class:`AsyncResult`,
            in addition it uses :meth:`join_native` if available for the
            current result backend.
            """
            return (self.join_native if self.supports_native_join else self.join)(
                timeout=timeout, propagate=propagate,
                interval=interval, callback=callback, no_ack=no_ack,
                on_message=on_message, disable_sync_subtasks=disable_sync_subtasks,
                on_interval=on_interval,
            )

        def join(self, timeout=None, propagate=True, interval=0.5,
                 callback=None, no_ack=True, on_message=None,
                 disable_sync_subtasks=True, on_interval=None):
            """Gather the results of all tasks as a list in order.

            Note:
                This can be an expensive operation for result store
                backends that must resort to polling (e.g., database).

                You should consider using :meth:`join_native` if your backend
                supports it.

            Warning:
                Waiting for tasks within a task may lead to deadlocks.
                Please see :ref:`task-synchronous-subtasks`.

            Arguments:
                timeout (float): The number of seconds to wait for results
                    before the operation times out.
                propagate (bool): If any of the tasks raises an exception,
                    the exception will be re-raised when this flag is set.
                interval (float): Time to wait (in seconds) before retrying to
                    retrieve a result from the set.  Note that this does not have
                    any effect when using the amqp result store backend,
                    as it does not use polling.
                callback (Callable): Optional callback to be called for every
                    result received.  Must have signature ``(task_id, value)``
                    No results will be returned by this function if a callback
                    is specified.  The order of results is also arbitrary when a
                    callback is used.  To get access to the result object for
                    a particular id you'll have to generate an index first:
                    ``index = {r.id: r for r in gres.results.values()}``
                    Or you can create new result objects on the fly:
                    ``result = app.AsyncResult(task_id)`` (both will
                    take advantage of the backend cache anyway).
                no_ack (bool): Automatic message acknowledgment (Note that if this
                    is set to :const:`False` then the messages
                    *will not be acknowledged*).
                disable_sync_subtasks (bool): Disable tasks to wait for sub tasks
                    this is the default configuration. CAUTION do not enable this
                    unless you must.

            Raises:
                celery.exceptions.TimeoutError: if ``timeout`` isn't
                    :const:`None` and the operation takes longer than ``timeout``
                    seconds.
            """
            if disable_sync_subtasks:
                assert_will_not_block()
            time_start = time.monotonic()
            remaining = None

            if on_message is not None:
                raise ImproperlyConfigured(
                    'Backend does not support on_message callback')

            results = []
            for result in self.results:
                remaining = None
                if timeout:
                    remaining = timeout - (time.monotonic() - time_start)
                    if remaining <= 0.0:
                        raise TimeoutError('join operation timed out')
                value = result.get(
                    timeout=remaining, propagate=propagate,
                    interval=interval, no_ack=no_ack, on_interval=on_interval,
                    disable_sync_subtasks=disable_sync_subtasks,
                )
                if callback:
                    callback(result.id, value)
                else:
                    results.append(value)
            return results

        def then(self, callback, on_error=None, weak=False):
            return self.on_ready.then(callback, on_error)

        def iter_native(self, timeout=None, interval=0.5, no_ack=True,
                        on_message=None, on_interval=None):
            """Backend optimized version of :meth:`iterate`.

            .. versionadded:: 2.2

            Note that this does not support collecting the results
            for different task types using different backends.

            This is currently only supported by the amqp, Redis and cache
            result backends.
            """
            return self.backend.iter_native(
                self,
                timeout=timeout, interval=interval, no_ack=no_ack,
                on_message=on_message, on_interval=on_interval,
            )

        def join_native(self, timeout=None, propagate=True,
                        interval=0.5, callback=None, no_ack=True,
                        on_message=None, on_interval=None,
                        disable_sync_subtasks=True):
            """Backend optimized version of :meth:`join`.

            .. versionadded:: 2.2

            Note that this does not support collecting the results
            for different task types using different backends.

            This is currently only supported by the amqp, Redis and cache
            result backends.
            """
            if disable_sync_subtasks:
                assert_will_not_block()
            order_index = None if callback else {
                result.id: i for i, result in enumerate(self.results)
            }
            acc = None if callback else [None for _ in range(len(self))]
            for task_id, meta in self.iter_native(timeout, interval, no_ack,
                                                  on_message, on_interval):
                if isinstance(meta, list):
                    value = []
                    for children_result in meta:
                        value.append(children_result.get())
                else:
                    value = meta['result']
                    if propagate and meta['status'] in states.PROPAGATE_STATES:
                        raise value
                if callback:
                    callback(task_id, value)
                else:
                    acc[order_index[task_id]] = value
            return acc

        def _iter_meta(self, **kwargs):
            return (meta for _, meta in self.backend.get_many(
                {r.id for r in self.results}, max_iterations=1, **kwargs
            ))

        def _failed_join_report(self):
            return (res for res in self.results
                    if res.backend.is_cached(res.id) and
                    res.state in states.PROPAGATE_STATES)

        def __len__(self):
            return len(self.results)

        def __eq__(self, other):
            if isinstance(other, ResultSet):
                return other.results == self.results
            return NotImplemented

        def __repr__(self):
            return f'<{type(self).__name__}: [{", ".join(r.id for r in self.results)}]>'

        @property
        def supports_native_join(self):
            try:
                return self.results[0].supports_native_join
            except IndexError:
                pass

        @property
        def app(self):
            if self._app is None:
                self._app = (self.results[0].app if self.results else
                             current_app._get_current_object())
            return self._app

        @app.setter
        def app(self, app):
            self._app = app

        @property
        def backend(self):
            return self.app.backend if self.app else self.results[0].backend

    @Thenable.register
    class GroupResult(ResultSet):
        """Like :class:`ResultSet`, but with an associated id.

        This type is returned by :class:`~celery.group`.

        It enables inspection of the tasks state and return values as
        a single entity.

        Arguments:
            id (str): The id of the group.
            results (Sequence[AsyncResult]): List of result instances.
            parent (ResultBase): Parent result of this group.
        """

        #: The UUID of the group.
        id = None

        #: List/iterator of results in the group
        results = None

        def __init__(self, id=None, results=None, parent=None, **kwargs):
            self.id = id
            self.parent = parent
            super().__init__(results, **kwargs)

        def _on_ready(self):
            self.backend.remove_pending_result(self)
            super()._on_ready()

        def save(self, backend=None):
            """Save group-result for later retrieval using :meth:`restore`.

            Example:
                >>> def save_and_restore(result):
                ...     result.save()
                ...     result = GroupResult.restore(result.id)
            """
            return (backend or self.app.backend).save_group(self.id, self)

        def delete(self, backend=None):
            """Remove this result if it was previously saved."""
            (backend or self.app.backend).delete_group(self.id)

        def __reduce__(self):
            return self.__class__, self.__reduce_args__()

        def __reduce_args__(self):
            return self.id, self.results

        def __bool__(self):
            return bool(self.id or self.results)
        __nonzero__ = __bool__  # Included for Py2 backwards compatibility

        def __eq__(self, other):
            if isinstance(other, GroupResult):
                return (
                    other.id == self.id and
                    other.results == self.results and
                    other.parent == self.parent
                )
            elif isinstance(other, str):
                return other == self.id
            return NotImplemented

        def __repr__(self):
            return f'<{type(self).__name__}: {self.id} [{", ".join(r.id for r in self.results)}]>'

        def __str__(self):
            """`str(self) -> self.id`."""
            return str(self.id)

        def __hash__(self):
            """`hash(self) -> hash(self.id)`."""
            return hash(self.id)

        def as_tuple(self):
            return (
                (self.id, self.parent and self.parent.as_tuple()),
                [r.as_tuple() for r in self.results]
            )

        @property
        def children(self):
            return self.results

        @classmethod
        def restore(cls, id, backend=None, app=None):
            """Restore previously saved group result."""
            app = app or (
                cls.app if not isinstance(cls.app, property) else current_app
            )
            backend = backend or app.backend
            return backend.restore_group(id)

    @Thenable.register
    class EagerResult(AsyncResult):
        """Result that we know has already been executed."""

        def __init__(self, id, ret_value, state, traceback=None, name=None):
            # pylint: disable=super-init-not-called
            # XXX should really not be inheriting from AsyncResult
            self.id = id
            self._result = ret_value
            self._state = state
            self._traceback = traceback
            self._name = name
            self.on_ready = promise()
            self.on_ready(self)

        def then(self, callback, on_error=None, weak=False):
            return self.on_ready.then(callback, on_error)

        def _get_task_meta(self):
            return self._cache

        def __reduce__(self):
            return self.__class__, self.__reduce_args__()

        def __reduce_args__(self):
            return (self.id, self._result, self._state, self._traceback)

        def __copy__(self):
            cls, args = self.__reduce__()
            return cls(*args)

        def ready(self):
            return True

        def get(self, timeout=None, propagate=True,
                disable_sync_subtasks=True, **kwargs):
            if disable_sync_subtasks:
                assert_will_not_block()

            if self.successful():
                return self.result
            elif self.state in states.PROPAGATE_STATES:
                if propagate:
                    raise self.result if isinstance(
                        self.result, Exception) else Exception(self.result)
                return self.result

        wait = get  # XXX Compat (remove 5.0)

        def forget(self):
            pass

        def revoke(self, *args, **kwargs):
            self._state = states.REVOKED

        def __repr__(self):
            return f'<EagerResult: {self.id}>'

        @property
        def _cache(self):
            return {
                'task_id': self.id,
                'result': self._result,
                'status': self._state,
                'traceback': self._traceback,
                'name': self._name,
            }

        @property
        def result(self):
            """The tasks return value."""
            return self._result

        @property
        def state(self):
            """The tasks state."""
            return self._state
        status = state

        @property
        def traceback(self):
            """The traceback if the task failed."""
            return self._traceback

        @property
        def supports_native_join(self):
            return False

    def result_from_tuple(r, app=None):
        """Deserialize result from tuple."""
        # earlier backends may just pickle, so check if
        # result is already prepared.
        app = app_or_default(app)
        Result = app.AsyncResult
        if not isinstance(r, ResultBase):
            res, nodes = r
            id, parent = res if isinstance(res, (list, tuple)) else (res, None)
            if parent:
                parent = result_from_tuple(parent, app)

            if nodes is not None:
                return app.GroupResult(
                    id, [result_from_tuple(child, app) for child in nodes],
                    parent=parent,
                )

            return Result(id, parent=parent)
        return r