improve error message and logic for _set_random_id exclusions

Author: alexcjohnson

dash/development/base_component.py

@@ -168,32 +168,37 @@ def __init__(self, **kwargs):
             setattr(self, k, v)
 
     def _set_random_id(self):
+
+        if hasattr(self, "id"):
+            return getattr(self, "id")
+
+        kind = f"`{self._namespace}.{self._type}`"  # pylint: disable=no-member
+
         if getattr(self, "persistence", False):
             raise RuntimeError(
-                """
+                f"""
                 Attempting to use an auto-generated ID with the `persistence` prop.
                 This is prohibited because persistence is tied to component IDs and
                 auto-generated IDs can easily change.
 
-                Please assign an explicit ID to this component.
-            """
+                Please assign an explicit ID to this {kind} component.
+                """
             )
         if "dash_snapshots" in sys.modules:
             raise RuntimeError(
-                """
+                f"""
                 Attempting to use an auto-generated ID in an app with `dash_snapshots`.
                 This is prohibited because snapshots saves the whole app layout,
                 including component IDs, and auto-generated IDs can easily change.
-                Callbacks referencing the new IDs will not work old snapshots.
+                Callbacks referencing the new IDs will not work with old snapshots.
 
-                Please assign an explicit ID to this component.
-            """
+                Please assign an explicit ID to this {kind} component.
+                """
             )
 
-        if not hasattr(self, "id"):
-            v = str(uuid.UUID(int=rd.randint(0, 2 ** 128)))
-            setattr(self, "id", v)
-        return getattr(self, "id")
+        v = str(uuid.UUID(int=rd.randint(0, 2 ** 128)))
+        setattr(self, "id", v)
+        return v
 
     def to_plotly_json(self):
         # Add normal properties

tests/unit/development/test_base_component.py

@@ -526,3 +526,11 @@ def update(v):
 
     assert "persistence" in e.value.args[0]
     assert "Please assign an explicit ID" in e.value.args[0]
+    assert "dash_core_components.Input" in e.value.args[0]
+
+    input1.id = "explicit"
+
+    # now it works without error
+    @app.callback(Output(output1, "children"), Input(input1, "value"))
+    def update2(v):
+        return f"Input 1 {v}"