add typing to function vars (#4372)

* add typing to function vars

* import ParamSpec from typing_extensions

* remove ellipsis as they are not supported in 3.9

* try importing everything from extensions

* special case 3.9

* don't use Any from extensions

* get typevar from extensions

reflex/event.py

@@ -45,6 +45,8 @@
 from reflex.vars.base import LiteralVar, Var
 from reflex.vars.function import (
     ArgsFunctionOperation,
+    ArgsFunctionOperationBuilder,
+    BuilderFunctionVar,
     FunctionArgs,
     FunctionStringVar,
     FunctionVar,
@@ -797,8 +799,7 @@ def scroll_to(elem_id: str, align_to_top: bool | Var[bool] = True) -> EventSpec:
     get_element_by_id = FunctionStringVar.create("document.getElementById")
 
     return run_script(
-        get_element_by_id(elem_id)
-        .call(elem_id)
+        get_element_by_id.call(elem_id)
         .to(ObjectVar)
         .scrollIntoView.to(FunctionVar)
         .call(align_to_top),
@@ -1580,7 +1581,7 @@ def create(
         )
 
 
-class EventChainVar(FunctionVar, python_types=EventChain):
+class EventChainVar(BuilderFunctionVar, python_types=EventChain):
     """Base class for event chain vars."""
 
 
@@ -1592,7 +1593,7 @@ class EventChainVar(FunctionVar, python_types=EventChain):
 # Note: LiteralVar is second in the inheritance list allowing it act like a
 # CachedVarOperation (ArgsFunctionOperation) and get the _js_expr from the
 # _cached_var_name property.
-class LiteralEventChainVar(ArgsFunctionOperation, LiteralVar, EventChainVar):
+class LiteralEventChainVar(ArgsFunctionOperationBuilder, LiteralVar, EventChainVar):
     """A literal event chain var."""
 
     _var_value: EventChain = dataclasses.field(default=None)  # type: ignore

reflex/utils/telemetry.py

@@ -51,7 +51,8 @@ def get_python_version() -> str:
     Returns:
         The Python version.
     """
-    return platform.python_version()
+    # Remove the "+" from the version string in case user is using a pre-release version.
+    return platform.python_version().rstrip("+")
 
 
 def get_reflex_version() -> str:

reflex/vars/base.py

@@ -361,21 +361,29 @@ def _var_is_string(self) -> bool:
         return False
 
     def __init_subclass__(
-        cls, python_types: Tuple[GenericType, ...] | GenericType = types.Unset, **kwargs
+        cls,
+        python_types: Tuple[GenericType, ...] | GenericType = types.Unset(),
+        default_type: GenericType = types.Unset(),
+        **kwargs,
     ):
         """Initialize the subclass.
 
         Args:
             python_types: The python types that the var represents.
+            default_type: The default type of the var. Defaults to the first python type.
             **kwargs: Additional keyword arguments.
         """
         super().__init_subclass__(**kwargs)
 
-        if python_types is not types.Unset:
+        if python_types or default_type:
             python_types = (
-                python_types if isinstance(python_types, tuple) else (python_types,)
+                (python_types if isinstance(python_types, tuple) else (python_types,))
+                if python_types
+                else ()
             )
 
+            default_type = default_type or (python_types[0] if python_types else Any)
+
             @dataclasses.dataclass(
                 eq=False,
                 frozen=True,
@@ -388,7 +396,7 @@ class ToVarOperation(ToOperation, cls):
                     default=Var(_js_expr="null", _var_type=None),
                 )
 
-                _default_var_type: ClassVar[GenericType] = python_types[0]
+                _default_var_type: ClassVar[GenericType] = default_type
 
             ToVarOperation.__name__ = f'To{cls.__name__.removesuffix("Var")}Operation'
 
@@ -588,6 +596,12 @@ def to(
         output: type[list] | type[tuple] | type[set],
     ) -> ArrayVar: ...
 
+    @overload
+    def to(
+        self,
+        output: type[dict],
+    ) -> ObjectVar[dict]: ...
+
     @overload
     def to(
         self, output: Type[ObjectVar], var_type: Type[VAR_INSIDE]