Clean up: use constants, remove unused code

Handle closing files with contextmanager

reflex/app.py

@@ -504,7 +504,7 @@ class App(MiddlewareMixin, LifespanMixin):
         if not self.api:
             return
         upload_is_used_marker = (
-            prerequisites.get_web_dir() / "backend" / "upload_is_used"
+            prerequisites.get_backend_dir() / constants.Dirs.UPLOAD_IS_USED
         )
         if Upload.is_used or upload_is_used_marker.exists():
             # To upload files.
@@ -982,11 +982,12 @@ class App(MiddlewareMixin, LifespanMixin):
             return str(datetime.now().time()).split(".")[0]
 
         should_compile = self._should_compile()
-        backend_dir = prerequisites.get_web_dir() / "backend"
+        backend_dir = prerequisites.get_backend_dir()
         if not should_compile and backend_dir.exists():
-            enable_state_marker = backend_dir / "enable_state"
-            if enable_state_marker.exists():
-                stateful_pages = json.load(enable_state_marker.open("r"))
+            stateful_pages_marker = backend_dir / constants.Dirs.STATEFUL_PAGES
+            if stateful_pages_marker.exists():
+                with stateful_pages_marker.open("r") as f:
+                    stateful_pages = json.load(f)
                 for route in stateful_pages:
                     console.info(f"BE Evaluating stateful page: {route}")
                     self._compile_page(route, save_page=False)
@@ -1235,9 +1236,12 @@ class App(MiddlewareMixin, LifespanMixin):
 
         # Pickle dynamic states
         if self._state is not None:
-            enable_state = prerequisites.get_web_dir() / "backend" / "enable_state"
-            enable_state.parent.mkdir(parents=True, exist_ok=True)
-            json.dump(list(self._stateful_pages), enable_state.open("w"))
+            stateful_pages_marker = (
+                prerequisites.get_backend_dir() / constants.Dirs.STATEFUL_PAGES
+            )
+            stateful_pages_marker.parent.mkdir(parents=True, exist_ok=True)
+            with stateful_pages_marker.open("w") as f:
+                json.dump(list(self._stateful_pages), f)
 
     @contextlib.asynccontextmanager
     async def modify_state(self, token: str) -> AsyncIterator[BaseState]:

reflex/constants/base.py

@@ -53,6 +53,12 @@ class Dirs(SimpleNamespace):
     POSTCSS_JS = "postcss.config.js"
     # The name of the states directory.
     STATES = ".states"
+    # Where compilation artifacts for the backend are stored.
+    BACKEND = "backend"
+    # JSON-encoded list of page routes that need to be evaluated on the backend.
+    STATEFUL_PAGES = "stateful_pages.json"
+    # Marker file indicating that upload component was used in the frontend.
+    UPLOAD_IS_USED = "upload_is_used"
 
 
 class Reflex(SimpleNamespace):

reflex/utils/prerequisites.py

@@ -98,6 +98,15 @@ def get_states_dir() -> Path:
     return environment.REFLEX_STATES_WORKDIR.get()
 
 
+def get_backend_dir() -> Path:
+    """Get the working directory for the backend.
+
+    Returns:
+        The working directory.
+    """
+    return get_web_dir() / constants.Dirs.BACKEND
+
+
 def check_latest_package_version(package_name: str):
     """Check if the latest version of the package is installed.
 

reflex/vars/base.py

@@ -1996,9 +1996,6 @@ class ComputedVar(Var[RETURN_TYPE]):
         default_factory=lambda: lambda _: None
     )  # pyright: ignore [reportAssignmentType]
 
-    # Flag determines whether we are pickling the computed var itself
-    _is_pickling: ClassVar[bool] = False
-
     def __init__(
         self,
         fget: Callable[[BASE_STATE], RETURN_TYPE],
@@ -2410,8 +2407,6 @@ class ComputedVar(Var[RETURN_TYPE]):
         Returns:
             The class of the var.
         """
-        if self._is_pickling:
-            return type(self)
         return FakeComputedVarBaseClass
 
     @property