is a Valid Prop

Author: 2Ryan09

dash/_callback.py

@@ -37,23 +37,13 @@
 from . import _validate
 from .long_callback.managers import BaseLongCallbackManager
 from ._callback_context import context_value
+from ._no_update import NoUpdate
 
 
 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 = []

dash/_no_update.py

@@ -0,0 +1,9 @@
+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"}
+        )

dash/_validate.py

@@ -6,6 +6,7 @@
 import flask
 
 from ._grouping import grouping_len, map_grouping
+from ._no_update import NoUpdate
 from .development.base_component import Component
 from . import exceptions
 from ._utils import (
@@ -211,8 +212,10 @@ def validate_multi_return(output_lists, output_values, callback_id):
 
 
 def fail_callback_output(output_value, output):
-    valid_children = (str, int, float, type(None), Component)
-    valid_props = (str, int, float, type(None), tuple, MutableSequence)
+    valid_children = (str, int, float, type(None), Component, NoUpdate)
+    valid_props = (str, int, float, type(None), tuple, MutableSequence, NoUpdate)
+
+    print("================================")
 
     def _raise_invalid(bad_val, outer_val, path, index=None, toplevel=False):
         bad_type = type(bad_val).__name__
@@ -261,6 +264,7 @@ def _valid_prop(val):
         return isinstance(val, valid_props)
 
     def _can_serialize(val):
+        print("checking ability to serialize")
         if not (_valid_child(val) or _valid_prop(val)):
             return False
         try:
@@ -272,6 +276,7 @@ def _can_serialize(val):
     def _validate_value(val, index=None):
         # val is a Component
         if isinstance(val, Component):
+            print("Is Component")
             unserializable_items = []
             # pylint: disable=protected-access
             for p, j in val._traverse_with_paths():
@@ -332,6 +337,7 @@ def _validate_value(val, index=None):
 
     if isinstance(output_value, list):
         for i, val in enumerate(output_value):
+            print(val)
             _validate_value(val, index=i)
     else:
         _validate_value(output_value)

test.py

@@ -0,0 +1,69 @@
+from types import SimpleNamespace
+
+import dash_bootstrap_components as dbc
+import plotly.graph_objects as go
+from dash import html, Dash, dcc, Input, Output, no_update, callback, dash_table
+
+
+app = Dash()
+
+app.layout = html.Div(
+        [
+            dbc.Alert(id="alert", is_open=False, duration=4000),
+            dcc.DatePickerRange(
+                id="date_picker",
+                start_date="2021-01-01",
+                end_date="2021-01-31",
+            ),
+            dcc.Graph(id="figcontainer"),
+            dash_table.DataTable(id="table"),
+        ]
+    )
+
+
+@callback(
+    Output(component_id="figcontainer", component_property="figure"),
+    Output(component_id="table", component_property="data"),
+    Output(component_id="alert", component_property="is_open"),
+    Output(component_id="alert", component_property="children"),
+    Input(component_id="date_picker", component_property="start_date"),
+    Input(component_id="date_picker", component_property="end_date"),
+)
+def update_graph(start, end):
+    df = get_bookings_in_interval(start, end)
+    # if there is no data, keep previous states and use alert
+    if type(df) is AssertionError:
+        return no_update, no_update, True, df
+
+    fig = go.Figure()
+
+    return (
+        fig.to_dict(),
+        {},
+        no_update,
+        no_update,
+    )
+
+mock_response = SimpleNamespace(
+    status_code=404,
+)
+
+# either returns a df or an AssertionError
+def get_bookings_in_interval(start, end):
+    df = None
+    try:
+        data = mock_response
+        assert data.status_code == 200, "Failed to fetch bookings"
+        parsed_data = dict(data.json())
+        assert len(parsed_data["bookings"]) > 0, "No items in Response"
+        # do something
+
+    except AssertionError as e:
+        print(e)
+        return e
+
+    return data
+
+
+if __name__ == '__main__':
+    app.run(debug=True)