Move Resource.takes_child() and Reosurce.takes_parent() exclusively to Action

Refs #2563 (comment)

Author: simonw

datasette/app.py

@@ -1609,7 +1609,9 @@ def _actions(self):
                 "description": action.description,
                 "takes_parent": action.takes_parent,
                 "takes_child": action.takes_child,
-                "resource_class": action.resource_class.__name__ if action.resource_class else None,
+                "resource_class": (
+                    action.resource_class.__name__ if action.resource_class else None
+                ),
                 "also_requires": action.also_requires,
             }
             for action in sorted(self.actions.values(), key=lambda a: a.name)

datasette/permissions.py

@@ -54,25 +54,6 @@ def private(self) -> bool:
     def private(self, value: bool):
         self._private = value
 
-    @classmethod
-    def takes_parent(cls) -> bool:
-        """
-        Whether actions on this resource can work with a parent.
-
-        Returns True for parent-level and child-level resources.
-        Returns False for top-level resources (where parent_class is None).
-        """
-        return cls.parent_class is not None
-
-    @classmethod
-    def takes_child(cls) -> bool:
-        """
-        Whether actions on this resource can work with a child.
-
-        - Top-level resources (no parent): False
-        - Child-level resources (has parent): True
-        """
-        return cls.parent_class is not None
 
     @classmethod
     def __init_subclass__(cls):
@@ -126,24 +107,25 @@ class Action:
     @property
     def takes_parent(self) -> bool:
         """
-        Whether this action requires a parent identifier.
+        Whether this action requires a parent identifier when instantiating its resource.
 
-        Returns False for global-only actions (no resource_class), otherwise delegates to resource_class.
+        Returns False for global-only actions (no resource_class).
+        Returns True for all actions with a resource_class (all resources require a parent identifier).
         """
-        if self.resource_class is None:
-            return False
-        return self.resource_class.takes_parent()
+        return self.resource_class is not None
 
     @property
     def takes_child(self) -> bool:
         """
-        Whether this action requires a child identifier.
+        Whether this action requires a child identifier when instantiating its resource.
 
-        Returns False for global-only actions (no resource_class), otherwise delegates to resource_class.
+        Returns False for global actions (no resource_class).
+        Returns False for parent-level resources (DatabaseResource - parent_class is None).
+        Returns True for child-level resources (TableResource, QueryResource - have a parent_class).
         """
         if self.resource_class is None:
             return False
-        return self.resource_class.takes_child()
+        return self.resource_class.parent_class is not None
 
 
 _reason_id = 1

docs/upgrade-1.0a20.md

@@ -86,7 +86,7 @@ def register_actions(datasette):
     ]
 ```
 
-The hierarchy information (whether an action takes parent/child parameters) is now determined by the `Resource` class, not the `Action`. For backward compatibility, `Action` still has `takes_parent` and `takes_child` properties that delegate to the resource class.
+The hierarchy information (whether an action takes parent/child parameters) is now derived from the `Resource` class hierarchy. `Action` has `takes_parent` and `takes_child` properties that are computed based on the `resource_class` and its `parent_class` attribute.
 
 ## permission_allowed() hook is replaced by permission_resources_sql()