do not validate non-cached var deps (#3576)

* do not validate non-cached var deps

* further improve Exceptions for misconfigured var deps

reflex/app.py

@@ -828,6 +828,8 @@ class App(LifespanMixin, Base):
             state = self.state
 
         for var in state.computed_vars.values():
+            if not var._cache:
+                continue
             deps = var._deps(objclass=state)
             for dep in deps:
                 if dep not in state.vars and dep not in state.backend_vars:

reflex/vars.py

@@ -36,7 +36,12 @@ from typing import (
 from reflex import constants
 from reflex.base import Base
 from reflex.utils import console, imports, serializers, types
-from reflex.utils.exceptions import VarAttributeError, VarTypeError, VarValueError
+from reflex.utils.exceptions import (
+    VarAttributeError,
+    VarDependencyError,
+    VarTypeError,
+    VarValueError,
+)
 
 # This module used to export ImportVar itself, so we still import it for export here
 from reflex.utils.imports import (
@@ -2233,10 +2238,14 @@ def computed_var(
 
     Raises:
         ValueError: If caching is disabled and an update interval is set.
+        VarDependencyError: If user supplies dependencies without caching.
     """
     if cache is False and interval is not None:
         raise ValueError("Cannot set update interval without caching.")
 
+    if cache is False and (deps is not None or auto_deps is False):
+        raise VarDependencyError("Cannot track dependencies without caching.")
+
     if fget is not None:
         return ComputedVar(fget=fget, cache=cache)
 

tests/test_app.py

@@ -1548,11 +1548,11 @@ def test_app_with_valid_var_dependencies(compilable_app: tuple[App, Path]):
         base: int = 0
         _backend: int = 0
 
-        @computed_var
+        @computed_var(cache=True)
         def foo(self) -> str:
             return "foo"
 
-        @computed_var(deps=["_backend", "base", foo])
+        @computed_var(deps=["_backend", "base", foo], cache=True)
         def bar(self) -> str:
             return "bar"
 
@@ -1564,7 +1564,7 @@ def test_app_with_invalid_var_dependencies(compilable_app: tuple[App, Path]):
     app, _ = compilable_app
 
     class InvalidDepState(BaseState):
-        @computed_var(deps=["foolksjdf"])
+        @computed_var(deps=["foolksjdf"], cache=True)
         def bar(self) -> str:
             return "bar"
 

tests/test_var.py

@@ -1406,6 +1406,7 @@ def cv_fget(state: BaseState) -> int:
 def test_computed_var_deps(deps: List[Union[str, Var]], expected: Set[str]):
     @computed_var(
         deps=deps,
+        cache=True,
     )
     def test_var(state) -> int:
         return 1
@@ -1426,6 +1427,7 @@ def test_invalid_computed_var_deps(deps: List):
 
         @computed_var(
             deps=deps,
+            cache=True,
         )
         def test_var(state) -> int:
             return 1