ComputedVar dependency tracking: require caller to pass objclass (#963)

Avoid issue where a ComputedVar is added to to a class dynamically, but does
not have a reference to the class its attached to, but requiring callers of the
`deps()` method to provide the objclass for looking up recursive method calls.

This allows for safer and more simplified determination of dependencies, even
in highly dynamic environments.

pynecone/state.py

@@ -104,7 +104,7 @@ class State(Base, ABC, extra=pydantic.Extra.allow):
         self.computed_var_dependencies = defaultdict(set)
         for cvar_name, cvar in self.computed_vars.items():
             # Add the dependencies.
-            for var in cvar.deps():
+            for var in cvar.deps(objclass=type(self)):
                 self.computed_var_dependencies[var].add(cvar_name)
 
         # Initialize the mutable fields.
@@ -492,9 +492,7 @@ class State(Base, ABC, extra=pydantic.Extra.allow):
                 func = arglist_factory(param)
             else:
                 continue
-            # link dynamically created ComputedVar to this state class for dep determination
-            func.__objclass__ = cls
-            func.fget.__name__ = param
+            func.fget.__name__ = param  # to allow passing as a prop
             cls.vars[param] = cls.computed_vars[param] = func.set_state(cls)  # type: ignore
             setattr(cls, param, func)
 

pynecone/var.py

@@ -825,9 +825,6 @@ class ComputedVar(Var, property):
 
         If the value is already cached on the instance, return the cached value.
 
-        If this ComputedVar doesn't know what type of object it is attached to, then save
-        a reference as self.__objclass__.
-
         Args:
             instance: the instance of the class accessing this computed var.
             owner: the class that this descriptor is attached to.
@@ -835,9 +832,6 @@ class ComputedVar(Var, property):
         Returns:
             The value of the var for the given instance.
         """
-        if not hasattr(self, "__objclass__"):
-            self.__objclass__ = owner
-
         if instance is None:
             return super().__get__(instance, owner)
 
@@ -846,21 +840,22 @@ class ComputedVar(Var, property):
             setattr(instance, self.cache_attr, super().__get__(instance, owner))
         return getattr(instance, self.cache_attr)
 
-    def deps(self, obj: Optional[FunctionType] = None) -> Set[str]:
+    def deps(
+        self,
+        objclass: Type,
+        obj: Optional[FunctionType] = None,
+    ) -> Set[str]:
         """Determine var dependencies of this ComputedVar.
 
         Save references to attributes accessed on "self".  Recursively called
         when the function makes a method call on "self".
 
         Args:
+            objclass: the class obj this ComputedVar is attached to.
             obj: the object to disassemble (defaults to the fget function).
 
         Returns:
             A set of variable names accessed by the given obj.
-
-        Raises:
-            RuntimeError: if this ComputedVar does not have a reference to the class
-                it is attached to. (Assign var.__objclass__ manually to workaround.)
         """
         d = set()
         if obj is None:
@@ -880,11 +875,12 @@ class ComputedVar(Var, property):
             if self_is_top_of_stack and instruction.opname == "LOAD_ATTR":
                 d.add(instruction.argval)
             elif self_is_top_of_stack and instruction.opname == "LOAD_METHOD":
-                if not hasattr(self, "__objclass__"):
-                    raise RuntimeError(
-                        f"ComputedVar {self.name!r} is not bound to a State subclass.",
+                d.update(
+                    self.deps(
+                        objclass=objclass,
+                        obj=getattr(objclass, instruction.argval),
                     )
-                d.update(self.deps(obj=getattr(self.__objclass__, instruction.argval)))
+                )
             self_is_top_of_stack = False
         return d
 

tests/test_app.py

@@ -120,7 +120,9 @@ def test_add_page_set_route_dynamic(app: App, index_page, windows_platform: bool
     app.add_page(index_page, route=route)
     assert set(app.pages.keys()) == {"test/[dynamic]"}
     assert "dynamic" in app.state.computed_vars
-    assert app.state.computed_vars["dynamic"].deps() == {"router_data"}
+    assert app.state.computed_vars["dynamic"].deps(objclass=DefaultState) == {
+        "router_data"
+    }
     assert "router_data" in app.state().computed_var_dependencies
 
 

tests/test_state.py

@@ -882,7 +882,11 @@ def test_conditional_computed_vars():
     assert ms._dirty_computed_vars(from_vars={"flag"}) == {"rendered_var"}
     assert ms._dirty_computed_vars(from_vars={"t2"}) == {"rendered_var"}
     assert ms._dirty_computed_vars(from_vars={"t1"}) == {"rendered_var"}
-    assert ms.computed_vars["rendered_var"].deps() == {"flag", "t1", "t2"}
+    assert ms.computed_vars["rendered_var"].deps(objclass=MainState) == {
+        "flag",
+        "t1",
+        "t2",
+    }
 
 
 def test_event_handlers_convert_to_fns(test_state, child_state):