Support Arbitrary callbacks

- Allow no output callback
- Add global set_props
- Fix side update pattern ids

Author: T4rk1n

.pylintrc

@@ -426,7 +426,7 @@ max-public-methods=40
 max-returns=6
 
 # Maximum number of statements in function / method body
-max-statements=50
+max-statements=75
 
 # Minimum number of public methods for a class (see R0903).
 min-public-methods=2

dash/__init__.py

@@ -18,7 +18,7 @@
 from . import html  # noqa: F401,E402
 from . import dash_table  # noqa: F401,E402
 from .version import __version__  # noqa: F401,E402
-from ._callback_context import callback_context  # noqa: F401,E402
+from ._callback_context import callback_context, set_props  # noqa: F401,E402
 from ._callback import callback, clientside_callback  # noqa: F401,E402
 from ._get_app import get_app  # noqa: F401,E402
 from ._get_paths import (  # noqa: F401,E402

dash/_callback.py

@@ -226,6 +226,7 @@ def insert_callback(
     manager=None,
     running=None,
     dynamic_creator=False,
+    no_output=False,
 ):
     if prevent_initial_call is None:
         prevent_initial_call = config_prevent_initial_callbacks
@@ -234,7 +235,7 @@ def insert_callback(
         output, prevent_initial_call, config_prevent_initial_callbacks
     )
 
-    callback_id = create_callback_id(output, inputs)
+    callback_id = create_callback_id(output, inputs, no_output)
     callback_spec = {
         "output": callback_id,
         "inputs": [c.to_dict() for c in inputs],
@@ -248,6 +249,7 @@ def insert_callback(
             "interval": long["interval"],
         },
         "dynamic_creator": dynamic_creator,
+        "no_output": no_output,
     }
     if running:
         callback_spec["running"] = running
@@ -262,6 +264,7 @@ def insert_callback(
         "raw_inputs": inputs,
         "manager": manager,
         "allow_dynamic_callbacks": dynamic_creator,
+        "no_output": no_output,
     }
     callback_list.append(callback_spec)
 
@@ -283,10 +286,12 @@ def register_callback(  # pylint: disable=R0914
         # Insert callback with scalar (non-multi) Output
         insert_output = output
         multi = False
+        no_output = False
     else:
         # Insert callback as multi Output
         insert_output = flatten_grouping(output)
         multi = True
+        no_output = len(output) == 0
 
     long = _kwargs.get("long")
     manager = _kwargs.get("manager")
@@ -315,6 +320,7 @@ def register_callback(  # pylint: disable=R0914
         manager=manager,
         dynamic_creator=allow_dynamic_callbacks,
         running=running,
+        no_output=no_output,
     )
 
     # pylint: disable=too-many-locals
@@ -333,7 +339,8 @@ def add_context(*args, **kwargs):
             app_callback_manager = kwargs.pop("long_callback_manager", None)
             callback_ctx = kwargs.pop("callback_context", {})
             callback_manager = long and long.get("manager", app_callback_manager)
-            _validate.validate_output_spec(insert_output, output_spec, Output)
+            if not no_output:
+                _validate.validate_output_spec(insert_output, output_spec, Output)
 
             context_value.set(callback_ctx)
 
@@ -443,6 +450,9 @@ def add_context(*args, **kwargs):
                         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
 
                 if output_value is callback_manager.UNDEFINED:
                     return to_json(response)
@@ -452,7 +462,10 @@ def add_context(*args, **kwargs):
             if NoUpdate.is_no_update(output_value):
                 raise PreventUpdate
 
-            if not multi:
+            if no_output:
+                output_value = []
+                flat_output_values = []
+            elif not multi:
                 output_value, output_spec = [output_value], [output_spec]
                 flat_output_values = output_value
             else:
@@ -464,23 +477,30 @@ def add_context(*args, **kwargs):
                 # Flatten grouping and validate grouping structure
                 flat_output_values = flatten_grouping(output_value, output)
 
-            _validate.validate_multi_return(
-                output_spec, flat_output_values, callback_id
-            )
-
             component_ids = collections.defaultdict(dict)
             has_update = False
-            for val, spec in zip(flat_output_values, output_spec):
-                if isinstance(val, NoUpdate):
-                    continue
-                for vali, speci in (
-                    zip(val, spec) if isinstance(spec, list) else [[val, spec]]
-                ):
-                    if not isinstance(vali, NoUpdate):
-                        has_update = True
-                        id_str = stringify_id(speci["id"])
-                        prop = clean_property_name(speci["property"])
-                        component_ids[id_str][prop] = vali
+            if not no_output:
+                _validate.validate_multi_return(
+                    output_spec, flat_output_values, callback_id
+                )
+
+                for val, spec in zip(flat_output_values, output_spec):
+                    if isinstance(val, NoUpdate):
+                        continue
+                    for vali, speci in (
+                        zip(val, spec) if isinstance(spec, list) else [[val, spec]]
+                    ):
+                        if not isinstance(vali, NoUpdate):
+                            has_update = True
+                            id_str = stringify_id(speci["id"])
+                            prop = clean_property_name(speci["property"])
+                            component_ids[id_str][prop] = vali
+
+            if not long:
+                side_update = dict(callback_ctx.updated_props)
+                if len(side_update) > 0:
+                    has_update = True
+                    response["sideUpdate"] = side_update
 
             if not has_update:
                 raise PreventUpdate

dash/_callback_context.py

@@ -2,6 +2,7 @@
 import warnings
 import json
 import contextvars
+import typing
 
 import flask
 
@@ -247,5 +248,20 @@ def using_outputs_grouping(self):
     def timing_information(self):
         return getattr(flask.g, "timing_information", {})
 
+    @has_context
+    def set_props(self, component_id: typing.Union[str, dict], props: dict):
+        ctx_value = _get_context_value()
+        if isinstance(component_id, dict):
+            ctx_value.updated_props[json.dumps(component_id)] = props
+        else:
+            ctx_value.updated_props[component_id] = props
+
 
 callback_context = CallbackContext()
+
+
+def set_props(component_id: typing.Union[str, dict], props: dict):
+    """
+    Set the props for a component not included in the callback outputs.
+    """
+    callback_context.set_props(component_id, props)

dash/_utils.py

@@ -131,7 +131,7 @@ def first(self, *names):
             return next(iter(self), {})
 
 
-def create_callback_id(output, inputs):
+def create_callback_id(output, inputs, no_output=False):
     # A single dot within a dict id key or value is OK
     # but in case of multiple dots together escape each dot
     # with `\` so we don't mistake it for multi-outputs
@@ -149,6 +149,12 @@ def _concat(x):
             _id += f"@{hashed_inputs}"
         return _id
 
+    if no_output:
+        # No output will hash the inputs.
+        return hashlib.sha256(
+            ".".join(str(x) for x in inputs).encode("utf-8")
+        ).hexdigest()
+
     if isinstance(output, (list, tuple)):
         return ".." + "...".join(_concat(x) for x in output) + ".."
 

dash/dash-renderer/src/actions/callbacks.ts

@@ -324,19 +324,37 @@ async function handleClientside(
     return result;
 }
 
-function sideUpdate(outputs: any, dispatch: any, paths: any) {
-    toPairs(outputs).forEach(([id, value]) => {
-        const [componentId, propName] = id.split('.');
-        const componentPath = paths.strs[componentId];
+function updateComponent(component_id: any, props: any) {
+    return function (dispatch: any, getState: any) {
+        const paths = getState().paths;
+        const componentPath = getPath(paths, component_id);
         dispatch(
             updateProps({
-                props: {[propName]: value},
+                props,
                 itempath: componentPath
             })
         );
-        dispatch(
-            notifyObservers({id: componentId, props: {[propName]: value}})
-        );
+        dispatch(notifyObservers({id: component_id, props}));
+    };
+}
+
+function sideUpdate(outputs: any, dispatch: any) {
+    toPairs(outputs).forEach(([id, value]) => {
+        let componentId, propName;
+        if (id.includes('.')) {
+            [componentId, propName] = id.split('.');
+            if (componentId.startsWith('{')) {
+                componentId = JSON.parse(componentId);
+            }
+            dispatch(updateComponent(componentId, {[propName]: value}));
+        } else {
+            if (id.startsWith('{')) {
+                componentId = JSON.parse(id);
+            } else {
+                componentId = id;
+            }
+            dispatch(updateComponent(componentId, value));
+        }
     });
 }
 
@@ -345,7 +363,6 @@ function handleServerside(
     hooks: any,
     config: any,
     payload: any,
-    paths: any,
     long: LongCallbackInfo | undefined,
     additionalArgs: [string, string, boolean?][] | undefined,
     getState: any,
@@ -365,7 +382,7 @@ function handleServerside(
     let moreArgs = additionalArgs;
 
     if (running) {
-        sideUpdate(running.running, dispatch, paths);
+        sideUpdate(running.running, dispatch);
         runningOff = running.runningOff;
     }
 
@@ -475,10 +492,10 @@ function handleServerside(
                     dispatch(removeCallbackJob({jobId: job}));
                 }
                 if (runningOff) {
-                    sideUpdate(runningOff, dispatch, paths);
+                    sideUpdate(runningOff, dispatch);
                 }
                 if (progressDefault) {
-                    sideUpdate(progressDefault, dispatch, paths);
+                    sideUpdate(progressDefault, dispatch);
                 }
             };
 
@@ -500,8 +517,12 @@ function handleServerside(
                         job = data.job;
                     }
 
+                    if (data.sideUpdate) {
+                        sideUpdate(data.sideUpdate, dispatch);
+                    }
+
                     if (data.progress) {
-                        sideUpdate(data.progress, dispatch, paths);
+                        sideUpdate(data.progress, dispatch);
                     }
                     if (!progressDefault && data.progressDefault) {
                         progressDefault = data.progressDefault;
@@ -696,11 +717,7 @@ export function executeCallback(
                         if (inter.length) {
                             additionalArgs.push(['cancelJob', job.jobId]);
                             if (job.progressDefault) {
-                                sideUpdate(
-                                    job.progressDefault,
-                                    dispatch,
-                                    paths
-                                );
+                                sideUpdate(job.progressDefault, dispatch);
                             }
                         }
                     }
@@ -713,7 +730,6 @@ export function executeCallback(
                             hooks,
                             newConfig,
                             payload,
-                            paths,
                             long,
                             additionalArgs.length ? additionalArgs : undefined,
                             getState,