adds allow_optional to State and Input to place no value as the placeholders

Author: BSd3v

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

@@ -122,22 +122,27 @@ function unwrapIfNotMulti(
 
     if (idProps.length !== 1) {
         if (!idProps.length) {
-            const isStr = typeof spec.id === 'string';
-            msg =
-                'A nonexistent object was used in an `' +
-                depType +
-                '` of a Dash callback. The id of this object is ' +
-                (isStr
-                    ? '`' + spec.id + '`'
-                    : JSON.stringify(spec.id) +
-                      (anyVals ? ' with MATCH values ' + anyVals : '')) +
-                ' and the property is `' +
-                spec.property +
-                (isStr
-                    ? '`. The string ids in the current layout are: [' +
-                      keys(paths.strs).join(', ') +
-                      ']'
-                    : '`. The wildcard ids currently available are logged above.');
+            if (spec.allow_optional) {
+                idProps = [{...spec, value: null}]
+                msg = ''
+            } else {
+                const isStr = typeof spec.id === 'string';
+                msg =
+                    'A nonexistent object was used in an `' +
+                    depType +
+                    '` of a Dash callback. The id of this object is ' +
+                    (isStr
+                        ? '`' + spec.id + '`'
+                        : JSON.stringify(spec.id) +
+                          (anyVals ? ' with MATCH values ' + anyVals : '')) +
+                    ' and the property is `' +
+                    spec.property +
+                    (isStr
+                        ? '`. The string ids in the current layout are: [' +
+                          keys(paths.strs).join(', ') +
+                          ']'
+                        : '`. The wildcard ids currently available are logged above.');
+            }
         } else {
             msg =
                 'Multiple objects were found for an `' +
@@ -203,7 +208,6 @@ function fillVals(
         // That's a real problem, so throw the first message as an error.
         refErr(errors, paths);
     }
-
     return inputVals;
 }
 

dash/dependencies.py

@@ -35,6 +35,7 @@ class DashDependency:  # pylint: disable=too-few-public-methods
     allow_duplicate: bool
     component_property: str
     allowed_wildcards: Sequence[_Wildcard]
+    allow_optional: bool
 
     def __init__(self, component_id: ComponentIdType, component_property: str):
 
@@ -45,6 +46,7 @@ def __init__(self, component_id: ComponentIdType, component_property: str):
 
         self.component_property = component_property
         self.allow_duplicate = False
+        self.allow_optional = False
 
     def __str__(self):
         return f"{self.component_id_str()}.{self.component_property}"
@@ -56,7 +58,8 @@ def component_id_str(self) -> str:
         return stringify_id(self.component_id)
 
     def to_dict(self) -> dict:
-        return {"id": self.component_id_str(), "property": self.component_property}
+        specs = {"id": self.component_id_str(), "property": self.component_property}
+        return {**specs, 'allow_optional': True} if self.allow_optional else specs
 
     def __eq__(self, other):
         """
@@ -133,14 +136,29 @@ def __init__(
 
 class Input(DashDependency):  # pylint: disable=too-few-public-methods
     """Input of callback: trigger an update when it is updated."""
-
-    allowed_wildcards = (MATCH, ALL, ALLSMALLER)
+    def __init__(
+        self,
+        component_id: ComponentIdType,
+        component_property: str,
+        allow_optional: bool = False,
+    ):
+        super().__init__(component_id, component_property)
+        self.allow_optional = allow_optional
+        self.allowed_wildcards = (MATCH, ALL, ALLSMALLER)
 
 
 class State(DashDependency):  # pylint: disable=too-few-public-methods
     """Use the value of a State in a callback but don't trigger updates."""
-
-    allowed_wildcards = (MATCH, ALL, ALLSMALLER)
+    def __init__(
+        self,
+        component_id: ComponentIdType,
+        component_property: str,
+        allow_optional: bool = False,
+    ):
+        super().__init__(component_id, component_property)
+        self.allow_optional = allow_optional
+        self.allowed_wildcards = (MATCH, ALL, ALLSMALLER)
+    # allowed_wildcards = (MATCH, ALL, ALLSMALLER)
 
 
 class ClientsideFunction:  # pylint: disable=too-few-public-methods