import collections import hashlib from functools import wraps from typing import Callable, Optional, Any, List, Tuple, Union import asyncio import flask from .dependencies import ( handle_callback_args, handle_grouped_callback_args, Output, ClientsideFunction, Input, ) from .development.base_component import ComponentRegistry from .exceptions import ( InvalidCallbackReturnValue, PreventUpdate, WildcardInLongCallback, MissingLongCallbackManagerError, BackgroundCallbackError, ImportedInsideCallbackError, ) from ._grouping import ( flatten_grouping, make_grouping_by_index, grouping_len, ) from ._utils import ( create_callback_id, stringify_id, to_json, coerce_to_list, AttributeDict, clean_property_name, ) from . import _validate from .background_callback.managers import BaseBackgroundCallbackManager from ._callback_context import context_value async def _async_invoke_callback( func, *args, **kwargs ): # used to mark the frame for the debugger # Check if the function is a coroutine function if asyncio.iscoroutinefunction(func): return await func(*args, **kwargs) # %% callback invoked %% # If the function is not a coroutine, call it directly return func(*args, **kwargs) # %% callback invoked %% def _invoke_callback(func, *args, **kwargs): # used to mark the frame for the debugger return func(*args, **kwargs) # %% callback invoked %% class NoUpdate: def to_plotly_json(self): # pylint: disable=no-self-use return {"_dash_no_update": "_dash_no_update"} @staticmethod def is_no_update(obj): return isinstance(obj, NoUpdate) or ( isinstance(obj, dict) and obj == {"_dash_no_update": "_dash_no_update"} ) GLOBAL_CALLBACK_LIST = [] GLOBAL_CALLBACK_MAP = {} GLOBAL_INLINE_SCRIPTS = [] # pylint: disable=too-many-locals def callback( *_args, background: bool = False, interval: int = 1000, progress: Optional[Union[List[Output], Output]] = None, progress_default: Any = None, running: Optional[List[Tuple[Output, Any, Any]]] = None, cancel: Optional[Union[List[Input], Input]] = None, manager: Optional[BaseBackgroundCallbackManager] = None, cache_args_to_ignore: Optional[list] = None, cache_ignore_triggered=True, on_error: Optional[Callable[[Exception], Any]] = None, **_kwargs, ) -> Callable[..., Any]: """ Normally used as a decorator, `@dash.callback` provides a server-side callback relating the values of one or more `Output` items to one or more `Input` items which will trigger the callback when they change, and optionally `State` items which provide additional information but do not trigger the callback directly. `@dash.callback` is an alternative to `@app.callback` (where `app = dash.Dash()`) introduced in Dash 2.0. It allows you to register callbacks without defining or importing the `app` object. The call signature is identical and it can be used instead of `app.callback` in all cases. The last, optional argument `prevent_initial_call` causes the callback not to fire when its outputs are first added to the page. Defaults to `False` and unlike `app.callback` is not configurable at the app level. :Keyword Arguments: :param background: Mark the callback as a background callback to execute in a manager for callbacks that take a long time without locking up the Dash app or timing out. :param manager: A background callback manager instance. Currently, an instance of one of `DiskcacheManager` or `CeleryManager`. Defaults to the `background_callback_manager` instance provided to the `dash.Dash constructor`. - A diskcache manager (`DiskcacheManager`) that runs callback logic in a separate process and stores the results to disk using the diskcache library. This is the easiest backend to use for local development. - A Celery manager (`CeleryManager`) that runs callback logic in a celery worker and returns results to the Dash app through a Celery broker like RabbitMQ or Redis. :param running: A list of 3-element tuples. The first element of each tuple should be an `Output` dependency object referencing a property of a component in the app layout. The second element is the value that the property should be set to while the callback is running, and the third element is the value the property should be set to when the callback completes. :param cancel: A list of `Input` dependency objects that reference a property of a component in the app's layout. When the value of this property changes while a callback is running, the callback is canceled. Note that the value of the property is not significant, any change in value will result in the cancellation of the running job (if any). This parameter only applies to background callbacks (`background=True`). :param progress: An `Output` dependency grouping that references properties of components in the app's layout. When provided, the decorated function will be called with an extra argument as the first argument to the function. This argument, is a function handle that the decorated function should call in order to provide updates to the app on its current progress. This function accepts a single argument, which correspond to the grouping of properties specified in the provided `Output` dependency grouping. This parameter only applies to background callbacks (`background=True`). :param progress_default: A grouping of values that should be assigned to the components specified by the `progress` argument when the callback is not in progress. If `progress_default` is not provided, all the dependency properties specified in `progress` will be set to `None` when the callback is not running. This parameter only applies to background callbacks (`background=True`). :param cache_args_to_ignore: Arguments to ignore when caching is enabled. If callback is configured with keyword arguments (Input/State provided in a dict), this should be a list of argument names as strings. Otherwise, this should be a list of argument indices as integers. This parameter only applies to background callbacks (`background=True`). :param cache_ignore_triggered: Whether to ignore which inputs triggered the callback when creating the cache. This parameter only applies to background callbacks (`background=True`). :param interval: Time to wait between the background callback update requests. :param on_error: Function to call when the callback raises an exception. Receives the exception object as first argument. The callback_context can be used to access the original callback inputs, states and output. """ background_spec = None config_prevent_initial_callbacks = _kwargs.pop( "config_prevent_initial_callbacks", False ) callback_map = _kwargs.pop("callback_map", GLOBAL_CALLBACK_MAP) callback_list = _kwargs.pop("callback_list", GLOBAL_CALLBACK_LIST) if background: background_spec: Any = { "interval": interval, } if manager: background_spec["manager"] = manager if progress: background_spec["progress"] = coerce_to_list(progress) validate_background_inputs(background_spec["progress"]) if progress_default: background_spec["progressDefault"] = coerce_to_list(progress_default) if not len(background_spec["progress"]) == len( background_spec["progressDefault"] ): raise Exception( "Progress and progress default needs to be of same length" ) if cancel: cancel_inputs = coerce_to_list(cancel) validate_background_inputs(cancel_inputs) background_spec["cancel"] = [c.to_dict() for c in cancel_inputs] background_spec["cancel_inputs"] = cancel_inputs if cache_args_to_ignore: background_spec["cache_args_to_ignore"] = cache_args_to_ignore background_spec["cache_ignore_triggered"] = cache_ignore_triggered return register_callback( callback_list, callback_map, config_prevent_initial_callbacks, *_args, **_kwargs, background=background_spec, manager=manager, running=running, on_error=on_error, ) def validate_background_inputs(deps): for dep in deps: if dep.has_wildcard(): raise WildcardInLongCallback( f""" background callbacks does not support dependencies with pattern-matching ids Received: {repr(dep)}\n""" ) ClientsideFuncType = Union[str, ClientsideFunction] def clientside_callback(clientside_function: ClientsideFuncType, *args, **kwargs): return register_clientside_callback( GLOBAL_CALLBACK_LIST, GLOBAL_CALLBACK_MAP, False, GLOBAL_INLINE_SCRIPTS, clientside_function, *args, **kwargs, ) # pylint: disable=too-many-arguments def insert_callback( callback_list, callback_map, config_prevent_initial_callbacks, output, outputs_indices, inputs, state, inputs_state_indices, prevent_initial_call, background=None, manager=None, running=None, dynamic_creator: Optional[bool] = False, no_output=False, ): if prevent_initial_call is None: prevent_initial_call = config_prevent_initial_callbacks _validate.validate_duplicate_output( output, prevent_initial_call, config_prevent_initial_callbacks ) callback_id = create_callback_id(output, inputs, no_output) callback_spec = { "output": callback_id, "inputs": [c.to_dict() for c in inputs], "state": [c.to_dict() for c in state], "clientside_function": None, # prevent_initial_call can be a string "initial_duplicates" # which should not prevent the initial call. "prevent_initial_call": prevent_initial_call is True, "background": background and { "interval": background["interval"], }, "dynamic_creator": dynamic_creator, "no_output": no_output, } if running: callback_spec["running"] = running callback_map[callback_id] = { "inputs": callback_spec["inputs"], "state": callback_spec["state"], "outputs_indices": outputs_indices, "inputs_state_indices": inputs_state_indices, "background": background, "output": output, "raw_inputs": inputs, "manager": manager, "allow_dynamic_callbacks": dynamic_creator, "no_output": no_output, } callback_list.append(callback_spec) return callback_id def _set_side_update(ctx, response) -> bool: side_update = dict(ctx.updated_props) if len(side_update) > 0: response["sideUpdate"] = side_update return True return False def _initialize_context(args, kwargs, inputs_state_indices, has_output, insert_output): """Initialize context and validate output specifications.""" app = kwargs.pop("app", None) output_spec = kwargs.pop("outputs_list") callback_ctx = kwargs.pop("callback_context", AttributeDict({"updated_props": {}})) context_value.set(callback_ctx) original_packages = set(ComponentRegistry.registry) if has_output: _validate.validate_output_spec(insert_output, output_spec, Output) func_args, func_kwargs = _validate.validate_and_group_input_args( args, inputs_state_indices ) return ( output_spec, callback_ctx, func_args, func_kwargs, app, original_packages, False, ) def _get_callback_manager( kwargs: dict, background: dict ) -> Union[BaseBackgroundCallbackManager, None]: """Set up the background callback and manage jobs.""" callback_manager = background.get( "manager", kwargs.get("background_callback_manager", None) ) if background is not None: if not callback_manager: raise MissingLongCallbackManagerError( "Running `background` callbacks requires a manager to be installed.\n" "Available managers:\n" "- Diskcache (`pip install dash[diskcache]`) to run callbacks in a separate Process" " and store results on the local filesystem.\n" "- Celery (`pip install dash[celery]`) to run callbacks in a celery worker" " and store results on redis.\n" ) old_job = flask.request.args.getlist("oldJob") if old_job: for job in old_job: callback_manager.terminate_job(job) return callback_manager def _setup_background_callback( kwargs, background, background_key, func, func_args, func_kwargs, callback_ctx ): """Set up the background callback and manage jobs.""" callback_manager = _get_callback_manager(kwargs, background) 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") ctx_value.pop("dash_response") job = callback_manager.call_job_fn( cache_key, job_fn, func_args if func_args else func_kwargs, ctx_value, ) data = { "cacheKey": cache_key, "job": job, } cancel = background.get("cancel") if cancel: data["cancel"] = cancel progress_default = background.get("progressDefault") if progress_default: data["progressDefault"] = { str(o): x for o, x in zip(progress_outputs, progress_default) } return to_json(data) def _progress_background_callback(response, callback_manager, background): progress_outputs = background.get("progress") cache_key = flask.request.args.get("cacheKey") if progress_outputs: # Get the progress before the result as it would be erased after the results. progress = callback_manager.get_progress(cache_key) if progress: response["progress"] = { str(x): progress[i] for i, x in enumerate(progress_outputs) } def _update_background_callback( error_handler, callback_ctx, response, kwargs, background, multi ): """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") _progress_background_callback(response, callback_manager, background) output_value = callback_manager.get_result(cache_key, job_id) return _handle_rest_background_callback( output_value, callback_manager, response, error_handler, callback_ctx, multi ) def _handle_rest_background_callback( output_value, callback_manager, response, error_handler, callback_ctx, multi, has_update=False, ): cache_key = flask.request.args.get("cacheKey") job_id = flask.request.args.get("job") # 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: # Job canceled -> no output to close the loop. output_value = NoUpdate() elif isinstance(output_value, dict) and "background_callback_error" in output_value: error = output_value.get("background_callback_error", {}) exc = BackgroundCallbackError( f"An error occurred inside a background callback: {error['msg']}\n{error['tb']}" ) if error_handler: output_value = error_handler(exc) if output_value is None: output_value = NoUpdate() # set_props from the error handler uses the original ctx # instead of manager.get_updated_props since it runs in the # request process. has_update = ( _set_side_update(callback_ctx, response) or output_value is not None ) else: raise exc if job_running and output_value is not callback_manager.UNDEFINED: # cached results. callback_manager.terminate_job(job_id) if multi and isinstance(output_value, (list, tuple)): output_value = [ NoUpdate() if NoUpdate.is_no_update(r) else r for r in output_value ] updated_props = callback_manager.get_updated_props(cache_key) if len(updated_props) > 0: response["sideUpdate"] = updated_props has_update = True if output_value is callback_manager.UNDEFINED: return to_json(response), has_update, True return output_value, has_update, False # pylint: disable=too-many-branches def _prepare_response( output_value, output_spec, multi, response, callback_ctx, app, original_packages, background, has_update, has_output, output, callback_id, allow_dynamic_callbacks, ): """Prepare the response object based on the callback output.""" component_ids = collections.defaultdict(dict) if has_output: if not multi: output_value, output_spec = [output_value], [output_spec] flat_output_values = output_value else: if isinstance(output_value, (list, tuple)): # For multi-output, allow top-level collection to be # list or tuple output_value = list(output_value) if NoUpdate.is_no_update(output_value): flat_output_values = [output_value] else: # Flatten grouping and validate grouping structure flat_output_values = flatten_grouping(output_value, output) if not NoUpdate.is_no_update(output_value): _validate.validate_multi_return( output_spec, flat_output_values, callback_id ) for val, spec in zip(flat_output_values, output_spec): if NoUpdate.is_no_update(val): continue for vali, speci in ( zip(val, spec) if isinstance(spec, list) else [[val, spec]] # type: ignore[reportArgumentType] ): if not NoUpdate.is_no_update(vali): has_update = True id_str = stringify_id(speci["id"]) prop = clean_property_name(speci["property"]) component_ids[id_str][prop] = vali else: if output_value is not None: raise InvalidCallbackReturnValue( f"No-output callback received return value: {output_value}" ) if not background: has_update = _set_side_update(callback_ctx, response) or has_output if not has_update: raise PreventUpdate if len(ComponentRegistry.registry) != len(original_packages): diff_packages = list( set(ComponentRegistry.registry).difference(original_packages) ) if not allow_dynamic_callbacks: raise ImportedInsideCallbackError( f"Component librar{'y' if len(diff_packages) == 1 else 'ies'} was imported during callback.\n" "You can set `_allow_dynamic_callbacks` to allow for development purpose only." ) dist = app.get_dist(diff_packages) response["dist"] = dist return response.update({"response": component_ids}) # pylint: disable=too-many-branches,too-many-statements def register_callback( callback_list, callback_map, config_prevent_initial_callbacks, *_args, **_kwargs ): ( output, flat_inputs, flat_state, inputs_state_indices, prevent_initial_call, ) = handle_grouped_callback_args(_args, _kwargs) if isinstance(output, Output): # Insert callback with scalar (non-multi) Output insert_output = output multi = False has_output = True else: # Insert callback as multi Output insert_output = flatten_grouping(output) multi = True has_output = len(output) > 0 background = _kwargs.get("background") manager = _kwargs.get("manager") running = _kwargs.get("running") on_error = _kwargs.get("on_error") if running is not None: if not isinstance(running[0], (list, tuple)): running = [running] running = { "running": {str(r[0]): r[1] for r in running}, "runningOff": {str(r[0]): r[2] for r in running}, } allow_dynamic_callbacks = _kwargs.get("_allow_dynamic_callbacks") output_indices = make_grouping_by_index(output, list(range(grouping_len(output)))) callback_id = insert_callback( callback_list, callback_map, config_prevent_initial_callbacks, insert_output, output_indices, flat_inputs, flat_state, inputs_state_indices, prevent_initial_call, background=background, manager=manager, dynamic_creator=allow_dynamic_callbacks, running=running, no_output=not has_output, ) # pylint: disable=too-many-locals def wrap_func(func): if background is None: background_key = None else: background_key = BaseBackgroundCallbackManager.register_func( func, background.get("progress") is not None, callback_id, ) @wraps(func) def add_context(*args, **kwargs): """Handles synchronous callbacks with context management.""" error_handler = on_error or kwargs.pop("app_on_error", None) ( output_spec, callback_ctx, func_args, func_kwargs, app, original_packages, has_update, ) = _initialize_context( args, kwargs, inputs_state_indices, has_output, insert_output ) response: dict = {"multi": True} jsonResponse = None try: if background is not None: if not flask.request.args.get("cacheKey"): return _setup_background_callback( kwargs, background, background_key, func, func_args, func_kwargs, callback_ctx, ) output_value, has_update, skip = _update_background_callback( error_handler, callback_ctx, response, kwargs, background, multi ) if skip: return output_value else: output_value = _invoke_callback(func, *func_args, **func_kwargs) # type: ignore[reportArgumentType] except PreventUpdate: raise except Exception as err: # pylint: disable=broad-exception-caught if error_handler: output_value = error_handler(err) if output_value is None and output_spec: output_value = NoUpdate() else: raise err _prepare_response( output_value, output_spec, multi, response, callback_ctx, app, original_packages, background, has_update, has_output, output, callback_id, allow_dynamic_callbacks, ) try: jsonResponse = to_json(response) except TypeError: _validate.fail_callback_output(output_value, output) return jsonResponse @wraps(func) async def async_add_context(*args, **kwargs): """Handles async callbacks with context management.""" error_handler = on_error or kwargs.pop("app_on_error", None) ( output_spec, callback_ctx, func_args, func_kwargs, app, original_packages, has_update, ) = _initialize_context( args, kwargs, inputs_state_indices, has_output, insert_output ) response: dict = {"multi": True} try: if background is not None: if not flask.request.args.get("cacheKey"): return _setup_background_callback( kwargs, background, background_key, func, func_args, func_kwargs, callback_ctx, ) output_value, has_update, skip = _update_background_callback( error_handler, callback_ctx, response, kwargs, background, multi ) if skip: return output_value else: output_value = await _async_invoke_callback( func, *func_args, **func_kwargs ) except PreventUpdate: raise except Exception as err: # pylint: disable=broad-exception-caught if error_handler: output_value = error_handler(err) if output_value is None and output_spec: output_value = NoUpdate() else: raise err _prepare_response( output_value, output_spec, multi, response, callback_ctx, app, original_packages, background, has_update, has_output, output, callback_id, allow_dynamic_callbacks, ) try: jsonResponse = to_json(response) except TypeError: _validate.fail_callback_output(output_value, output) return jsonResponse if asyncio.iscoroutinefunction(func): callback_map[callback_id]["callback"] = async_add_context else: callback_map[callback_id]["callback"] = add_context return func return wrap_func _inline_clientside_template = """ (function() {{ var clientside = window.dash_clientside = window.dash_clientside || {{}}; var ns = clientside["{namespace}"] = clientside["{namespace}"] || {{}}; ns["{function_name}"] = {clientside_function}; }})(); """ def register_clientside_callback( callback_list, callback_map, config_prevent_initial_callbacks, inline_scripts, clientside_function: ClientsideFuncType, *args, **kwargs, ): output, inputs, state, prevent_initial_call = handle_callback_args(args, kwargs) no_output = isinstance(output, (list,)) and len(output) == 0 insert_callback( callback_list, callback_map, config_prevent_initial_callbacks, output, None, inputs, state, None, prevent_initial_call, no_output=no_output, ) # If JS source is explicitly given, create a namespace and function # name, then inject the code. if isinstance(clientside_function, str): namespace = "_dashprivate_clientside_funcs" # Create a hash from the function, it will be the same always function_name = hashlib.sha256(clientside_function.encode("utf-8")).hexdigest() inline_scripts.append( _inline_clientside_template.format( namespace=namespace, function_name=function_name, clientside_function=clientside_function, ) ) # Callback is stored in an external asset. else: namespace = clientside_function.namespace function_name = clientside_function.function_name callback_list[-1]["clientside_function"] = { "namespace": namespace, "function_name": function_name, }