import collections import hashlib from functools import wraps from typing import Callable, Optional, Any import flask from .dependencies import ( handle_callback_args, handle_grouped_callback_args, Output, ) from .development.base_component import ComponentRegistry from .exceptions import ( InvalidCallbackReturnValue, PreventUpdate, WildcardInLongCallback, MissingLongCallbackManagerError, LongCallbackError, 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 .long_callback.managers import BaseLongCallbackManager from ._callback_context import context_value 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=False, interval=1000, progress=None, progress_default=None, running=None, cancel=None, manager=None, cache_args_to_ignore=None, on_error: Optional[Callable[[Exception], Any]] = None, **_kwargs, ): """ 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 long 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 long 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). :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 :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. :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. :param interval: Time to wait between the long 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. """ long_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: long_spec = { "interval": interval, } if manager: long_spec["manager"] = manager if progress: long_spec["progress"] = coerce_to_list(progress) validate_long_inputs(long_spec["progress"]) if progress_default: long_spec["progressDefault"] = coerce_to_list(progress_default) if not len(long_spec["progress"]) == len(long_spec["progressDefault"]): raise Exception( "Progress and progress default needs to be of same length" ) if cancel: cancel_inputs = coerce_to_list(cancel) validate_long_inputs(cancel_inputs) long_spec["cancel"] = [c.to_dict() for c in cancel_inputs] long_spec["cancel_inputs"] = cancel_inputs if cache_args_to_ignore: long_spec["cache_args_to_ignore"] = cache_args_to_ignore return register_callback( callback_list, callback_map, config_prevent_initial_callbacks, *_args, **_kwargs, long=long_spec, manager=manager, running=running, on_error=on_error, ) def validate_long_inputs(deps): for dep in deps: if dep.has_wildcard(): raise WildcardInLongCallback( f""" long callbacks does not support dependencies with pattern-matching ids Received: {repr(dep)}\n""" ) def clientside_callback(clientside_function, *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, long=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, "long": long and { "interval": long["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, "long": long, "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 # 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 long = _kwargs.get("long") 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, long=long, manager=manager, dynamic_creator=allow_dynamic_callbacks, running=running, no_output=not has_output, ) # pylint: disable=too-many-locals def wrap_func(func): if long is not None: long_key = BaseLongCallbackManager.register_func( func, long.get("progress") is not None, callback_id, ) @wraps(func) def add_context(*args, **kwargs): output_spec = kwargs.pop("outputs_list") app_callback_manager = kwargs.pop("long_callback_manager", None) callback_ctx = kwargs.pop( "callback_context", AttributeDict({"updated_props": {}}) ) app = kwargs.pop("app", None) callback_manager = long and long.get("manager", app_callback_manager) error_handler = on_error or kwargs.pop("app_on_error", None) original_packages = set(ComponentRegistry.registry) if has_output: _validate.validate_output_spec(insert_output, output_spec, Output) context_value.set(callback_ctx) func_args, func_kwargs = _validate.validate_and_group_input_args( args, inputs_state_indices ) response: dict = {"multi": True} has_update = False if long is not None: if not callback_manager: raise MissingLongCallbackManagerError( "Running `long` 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" ) progress_outputs = long.get("progress") cache_key = flask.request.args.get("cacheKey") job_id = flask.request.args.get("job") old_job = flask.request.args.getlist("oldJob") current_key = callback_manager.build_cache_key( func, # Inputs provided as dict is kwargs. func_args if func_args else func_kwargs, long.get("cache_args_to_ignore", []), ) if old_job: for job in old_job: callback_manager.terminate_job(job) if not cache_key: cache_key = current_key job_fn = callback_manager.func_registry.get(long_key) job = callback_manager.call_job_fn( cache_key, job_fn, func_args if func_args else func_kwargs, AttributeDict( args_grouping=callback_ctx.args_grouping, using_args_grouping=callback_ctx.using_args_grouping, outputs_grouping=callback_ctx.outputs_grouping, using_outputs_grouping=callback_ctx.using_outputs_grouping, inputs_list=callback_ctx.inputs_list, states_list=callback_ctx.states_list, outputs_list=callback_ctx.outputs_list, input_values=callback_ctx.input_values, state_values=callback_ctx.state_values, triggered_inputs=callback_ctx.triggered_inputs, ignore_register_page=True, ), ) data = { "cacheKey": cache_key, "job": job, } cancel = long.get("cancel") if cancel: data["cancel"] = cancel progress_default = long.get("progressDefault") if progress_default: data["progressDefault"] = { str(o): x for o, x in zip(progress_outputs, progress_default) } return to_json(data) 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) } output_value = callback_manager.get_result(cache_key, job_id) # 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 "long_callback_error" in output_value ): error = output_value.get("long_callback_error", {}) exc = LongCallbackError( f"An error occurred inside a long 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) else: try: output_value = _invoke_callback(func, *func_args, **func_kwargs) except PreventUpdate as err: raise err except Exception as err: # pylint: disable=broad-exception-caught if error_handler: output_value = error_handler(err) # If the error returns nothing, automatically puts NoUpdate for response. if output_value is None: output_value = NoUpdate() else: raise err 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]] ): 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}" ) output_value = [] flat_output_values = [] if not long: has_update = _set_side_update(callback_ctx, response) or has_update if not has_update: raise PreventUpdate response["response"] = component_ids 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 try: jsonResponse = to_json(response) except TypeError: _validate.fail_callback_output(output_value, output) return jsonResponse 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, *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, }