Improved callback_context

CHANGELOG.md

@@ -5,6 +5,12 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 ## [Unreleased]
 
 ### Added
+- [#1952](https://github.com/plotly/dash/pull/1952) Improved callback_context
+  - Closes [#1818](https://github.com/plotly/dash/issues/1818) Closes [#1054](https://github.com/plotly/dash/issues/1054)
+  - adds `dash.ctx`, a more concise name for `dash.callback_context`
+  - adds `ctx.triggered_prop_ids`, a dictionary of the component ids and props that triggered the callback.
+  - adds `ctx.triggered_id`, the `id` of the component that triggered the callback.
+  - adds `ctx.args_grouping`, a dict of the inputs used with flexible callback signatures.
 
 - [#2009](https://github.com/plotly/dash/pull/2009) Add support for Promises within Client-side callbacks as requested in [#1364](https://github.com/plotly/dash/pull/1364).
 

dash/__init__.py

@@ -26,3 +26,4 @@
     get_relative_path,
     strip_relative_path,
 )
+ctx = callback_context

dash/_callback_context.py

@@ -1,9 +1,11 @@
 import functools
 import warnings
-
+import json
+from copy import deepcopy
 import flask
 
 from . import exceptions
+from ._utils import stringify_id, AttributeDict
 
 
 def has_context(func):
@@ -46,16 +48,158 @@ def states(self):
     @property
     @has_context
     def triggered(self):
+        """
+        Returns a list of all the Input props that changed and caused the callback to execute. It is empty when the
+        callback is called on initial load, unless an Input prop got its value from another initial callback.
+        Callbacks triggered by user actions typically have one item in triggered, unless the same action changes
+        two props at once or the callback has several Input props that are all modified by another callback based on
+        a single user action.
+
+        Example:  To get the id of the component that triggered the callback:
+        `component_id = ctx.triggered[0]['prop_id'].split('.')[0]`
+
+        Example:  To detect initial call, empty triggered is not really empty, it's falsy so that you can use:
+        `if ctx.triggered:`
+        """
         # For backward compatibility: previously `triggered` always had a
         # value - to avoid breaking existing apps, add a dummy item but
         # make the list still look falsy. So `if ctx.triggered` will make it
         # look empty, but you can still do `triggered[0]["prop_id"].split(".")`
         return getattr(flask.g, "triggered_inputs", []) or falsy_triggered
 
+    @property
+    @has_context
+    def triggered_prop_ids(self):
+        """
+        Returns a dictionary of all the Input props that changed and caused the callback to execute. It is empty when
+        the callback is called on initial load, unless an Input prop got its value from another initial callback.
+        Callbacks triggered by user actions typically have one item in triggered, unless the same action changes
+        two props at once or the callback has several Input props that are all modified by another callback based
+        on a single user action.
+
+        triggered_prop_ids (dict):
+        - keys (str) : the triggered "prop_id" composed of "component_id.component_property"
+        - values (str or dict): the id of the component that triggered the callback. Will be the dict id for pattern matching callbacks
+
+        Example - regular callback
+        {"btn-1.n_clicks": "btn-1"}
+
+        Example - pattern matching callbacks:
+        {'{"index":0,"type":"filter-dropdown"}.value': {"index":0,"type":"filter-dropdown"}}
+
+        Example usage:
+        `if "btn-1.n_clicks" in ctx.triggered_prop_ids:
+            do_something()`
+        """
+        triggered = getattr(flask.g, "triggered_inputs", [])
+        ids = AttributeDict({})
+        for item in triggered:
+            component_id, _, _ = item["prop_id"].rpartition(".")
+            ids[item["prop_id"]] = component_id
+            if component_id.startswith("{"):
+                ids[item["prop_id"]] = AttributeDict(json.loads(component_id))
+        return ids
+
+    @property
+    @has_context
+    def triggered_id(self):
+        """
+        Returns the component id (str or dict) of the Input component that triggered the callback.
+
+        Note - use `triggered_prop_ids` if you need both the component id and the prop that triggered the callback or if
+        multiple Inputs triggered the callback.
+
+        Example usage:
+        `if "btn-1" == ctx.triggered_id:
+            do_something()`
+
+        """
+        component_id = None
+        if self.triggered:
+            prop_id = self.triggered_prop_ids.first()
+            component_id = self.triggered_prop_ids[prop_id]
+        return component_id
+
     @property
     @has_context
     def args_grouping(self):
-        return getattr(flask.g, "args_grouping", [])
+        """
+        args_grouping is a dict of the inputs used with flexible callback signatures. The keys are the variable names
+        and the values are dictionaries containing:
+        - “id”: (string or dict) the component id. If it’s a pattern matching id, it will be a dict.
+        - “id_str”: (str) for pattern matching ids, it’s the strigified dict id with no white spaces.
+        - “property”: (str) The component property used in the callback.
+        - “value”: the value of the component property at the time the callback was fired.
+        - “triggered”: (bool)Whether this input triggered the callback.
+
+        Example usage:
+        @app.callback(
+            Output("container", "children"),
+            inputs=dict(btn1=Input("btn-1", "n_clicks"), btn2=Input("btn-2", "n_clicks")),
+        )
+        def display(btn1, btn2):
+            c = ctx.args_grouping
+            if c.btn1.triggered:
+                return f"Button 1 clicked {btn1} times"
+            elif c.btn2.triggered:
+                return f"Button 2 clicked {btn2} times"
+            else:
+               return "No clicks yet"
+
+        """
+        triggered = getattr(flask.g, "triggered_inputs", [])
+        triggered = [item["prop_id"] for item in triggered]
+        grouping = getattr(flask.g, "args_grouping", {})
+
+        def update_args_grouping(g):
+            if isinstance(g, dict) and "id" in g:
+                str_id = stringify_id(g["id"])
+                prop_id = f"{str_id}.{g['property']}"
+
+                new_values = {
+                    "value": g.get("value"),
+                    "str_id": str_id,
+                    "triggered": prop_id in triggered,
+                    "id": AttributeDict(g["id"])
+                    if isinstance(g["id"], dict)
+                    else g["id"],
+                }
+                g.update(new_values)
+
+        def recursive_update(g):
+            if isinstance(g, (tuple, list)):
+                for i in g:
+                    update_args_grouping(i)
+                    recursive_update(i)
+            if isinstance(g, dict):
+                for i in g.values():
+                    update_args_grouping(i)
+                    recursive_update(i)
+
+        recursive_update(grouping)
+
+        return grouping
+
+    # todo not sure whether we need this, but it removes a level of nesting so
+    #  you don't need to use `.value` to get the value.
+    @property
+    @has_context
+    def args_grouping_values(self):
+        grouping = getattr(flask.g, "args_grouping", {})
+        grouping = deepcopy(grouping)
+
+        def recursive_update(g):
+            if isinstance(g, (tuple, list)):
+                for i in g:
+                    recursive_update(i)
+            if isinstance(g, dict):
+                for k, v in g.items():
+                    if isinstance(v, dict) and "id" in v:
+                        g[k] = v["value"]
+                    recursive_update(v)
+
+        recursive_update(grouping)
+        return grouping
 
     @property
     @has_context

dash/_grouping.py

@@ -14,6 +14,7 @@
 
 """
 from dash.exceptions import InvalidCallbackReturnValue
+from ._utils import AttributeDict
 
 
 def flatten_grouping(grouping, schema=None):
@@ -123,14 +124,14 @@ def map_grouping(fn, grouping):
         return [map_grouping(fn, g) for g in grouping]
 
     if isinstance(grouping, dict):
-        return {k: map_grouping(fn, g) for k, g in grouping.items()}
+        return AttributeDict({k: map_grouping(fn, g) for k, g in grouping.items()})
 
     return fn(grouping)
 
 
 def make_grouping_by_key(schema, source, default=None):
     """
-    Create a grouping from a schema by ujsing the schema's scalar values to look up
+    Create a grouping from a schema by using the schema's scalar values to look up
     items in the provided source object.
 
     :param schema: A grouping of potential keys in source

dash/_utils.py

@@ -119,6 +119,8 @@ def first(self, *names):
             value = self.get(name)
             if value:
                 return value
+        if not names:
+            return next(iter(self), {})
 
 
 def create_callback_id(output):
@@ -152,7 +154,7 @@ def stringify_id(id_):
 
 
 def inputs_to_dict(inputs_list):
-    inputs = {}
+    inputs = AttributeDict()
     for i in inputs_list:
         inputsi = i if isinstance(i, list) else [i]
         for ii in inputsi:
@@ -161,6 +163,16 @@ def inputs_to_dict(inputs_list):
     return inputs
 
 
+def convert_to_AttributeDict(nested_list):
+    new_dict = []
+    for i in nested_list:
+        if isinstance(i, dict):
+            new_dict.append(AttributeDict(i))
+        else:
+            new_dict.append([AttributeDict(ii) for ii in i])
+    return new_dict
+
+
 def inputs_to_vals(inputs):
     return [
         [ii.get("value") for ii in i] if isinstance(i, list) else i.get("value")

dash/_validate.py

@@ -134,6 +134,11 @@ def validate_and_group_input_args(flat_args, arg_index_grouping):
     if isinstance(arg_index_grouping, dict):
         func_args = []
         func_kwargs = args_grouping
+        for key in func_kwargs:
+            if not key.isidentifier():
+                raise exceptions.CallbackException(
+                    f"{key} is not a valid Python variable name"
+                )
     elif isinstance(arg_index_grouping, (tuple, list)):
         func_args = list(args_grouping)
         func_kwargs = {}

dash/dash.py

@@ -49,6 +49,7 @@
     patch_collections_abc,
     split_callback_id,
     to_json,
+    convert_to_AttributeDict,
     gen_salt,
 )
 from . import _callback
@@ -1297,6 +1298,7 @@ def callback(_triggers, user_store_data, user_callback_args):
 
     def dispatch(self):
         body = flask.request.get_json()
+
         flask.g.inputs_list = inputs = body.get(  # pylint: disable=assigning-non-slot
             "inputs", []
         )
@@ -1331,9 +1333,12 @@ def dispatch(self):
             # Add args_grouping
             inputs_state_indices = cb["inputs_state_indices"]
             inputs_state = inputs + state
+            inputs_state = convert_to_AttributeDict(inputs_state)
+
             args_grouping = map_grouping(
                 lambda ind: inputs_state[ind], inputs_state_indices
             )
+
             flask.g.args_grouping = args_grouping  # pylint: disable=assigning-non-slot
             flask.g.using_args_grouping = (  # pylint: disable=assigning-non-slot
                 not isinstance(inputs_state_indices, int)

tests/integration/callbacks/test_callback_context.py

@@ -2,7 +2,7 @@
 import operator
 import pytest
 
-from dash import Dash, Input, Output, html, dcc, callback_context
+from dash import Dash, ALL, Input, Output, html, dcc, callback_context, ctx
 
 from dash.exceptions import PreventUpdate, MissingCallbackContextException
 import dash.testing.wait as wait
@@ -330,3 +330,59 @@ def update_results(n1, n2, nsum):
     assert len(keys1) == 2
     assert "sum-number.value" in keys1
     assert "input-number-2.value" in keys1
+
+
+def test_cbcx007_triggered_id(dash_duo):
+    app = Dash(__name__)
+
+    btns = ["btn-{}".format(x) for x in range(1, 6)]
+
+    app.layout = html.Div(
+        [html.Div([html.Button(btn, id=btn) for btn in btns]), html.Div(id="output")]
+    )
+
+    @app.callback(Output("output", "children"), [Input(x, "n_clicks") for x in btns])
+    def on_click(*args):
+        if not ctx.triggered:
+            raise PreventUpdate
+        for btn in btns:
+            if btn in ctx.triggered_prop_ids.values():
+                assert btn == ctx.triggered_id
+                return f"Just clicked {btn}"
+
+    dash_duo.start_server(app)
+
+    for i in range(1, 5):
+        for btn in btns:
+            dash_duo.find_element("#" + btn).click()
+            dash_duo.wait_for_text_to_equal("#output", f"Just clicked {btn}")
+
+
+def test_cbcx008_triggered_id_pmc(dash_duo):
+
+    app = Dash()
+    app.layout = html.Div(
+        [
+            html.Button("Click me", id={"type": "btn", "index": "myindex"}),
+            html.Div(id="output"),
+        ]
+    )
+
+    @app.callback(
+        Output("output", "children"), Input({"type": "btn", "index": ALL}, "n_clicks")
+    )
+    def func(n_clicks):
+        if ctx.triggered:
+            triggered_id, dict_id = next(iter(ctx.triggered_prop_ids.items()))
+
+            assert dict_id == ctx.triggered_id
+
+            if dict_id == {"type": "btn", "index": "myindex"}:
+                return dict_id["index"]
+
+    dash_duo.start_server(app)
+
+    dash_duo.find_element(
+        '#\\{\\"index\\"\\:\\"myindex\\"\\,\\"type\\"\\:\\"btn\\"\\}'
+    ).click()
+    dash_duo.wait_for_text_to_equal("#output", "myindex")