Add contains, reverse operations for Var

[martinxu9]

Summary

• Add reverse operation for list type Var.
• Add contains operation for list/tuple/dict/str type Var, overrides __contains__ to raise since this cannot be used to return a Var at the end, it gets converted to boolean.
• UTs for reverse and contains.
• Pending: add code snippet/example app

Tests

• new UTs

Examples

• foreach renders list of texts in the reverse order
• text box at the bottom shows a boolean printed as string for whether the user typed input is in the list of words.

class State(rx.State):
    """The app state."""
    words: List[str] = ["Hello", "world", "from", "Reflex!"]
    typed_word: str = ""

def index() -> rx.Component:
    return rx.vstack(
        rx.foreach(State.words.reverse(), lambda word: rx.text(word)),
        rx.input(value=State.typed_word, on_change=State.set_typed_word, style=dict(width="10vw")),
        rx.text("Did I type a word in the above?"),
        rx.text(State.words.contains(State.typed_word).to_string()),
    )

[masenf]

is there a reason why to not support the native python in operator? do we lose control over the right hand side or something?

[martinxu9]

so the return of __contains__ seems to be automatically converted to boolean, so instead of something like a var with {[1,2,3].includes(1)}, we get True (the var being eval as a boolean).

[masenf]

is there a reason to use self.full_name here instead of just self? the __str__ function selectively uses self.full_name in some situations, otherwise wraps the var, or formats it as a str. is it the wrapping with { and } that's causing the problem?

[martinxu9]

Yes did not want the enclosing curly brackets.

[masenf]

this gives me hydration errors when i try it in dev mode because it will reverse the state var in place.

Suggested change

	name=f"{self.full_name}.reverse()",
	name=f"[...{self.full_name}].reverse()",

(render functions are not allowed to mutate values)

[martinxu9]

👍🏼

[masenf]

when the var's type_ is None, this gives a really confusing error

  File "/Users/masenf/code/reflex-dev/repro-contains/repro_contains/repro_contains.py", line 27, in index
    rx.foreach(rx.vars.BaseVar(name="['foo', 'me', 'you']").reverse(), rx.text),
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/masenf/code/reflex-dev/reflex/reflex/vars.py", line 748, in reverse
    if not types._issubclass(self.type_, list):
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/masenf/code/reflex-dev/reflex/reflex/utils/types.py", line 115, in _issubclass
    return cls_check_base == Any or issubclass(cls_base, cls_check_base)
                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: issubclass() arg 1 must be a class

[martinxu9]

good catch, thanks. Added another place to check None first; also added test with var type_ is None

[martinxu9]

@picklelo Added some example code

[martinxu9]

@masenf new upload incorporating comments and suggestions