Issue with iterator with non numerical key

[Schwartzmorn]

Hello !

I have been trying Leptos to discover both the world of Rust and web assembly because I dream of the day I'll be able to write a front end in a type safe language. I was enticed by Leptos view! macro and heard good things about it in general, so I decided to try it out. In short I'm fairly new to both Rust and web assembly.

I have been struggling with something that should be simple IMO. I have a stream of values that come in a random order, and want to display them in alphabetical order as they arrive, but my code keeps panicking with the error panicked at 'index out of bounds: the len is 5 but the index is 5.

After simplifying my code as much as I could, here is the smallest reproducer I have:

use leptos::*;

static VALUES: [&str; 26] = ["AA", "BB", "CC", "DD", "EE", "FF", "GG", "HH", "II", "JJ", "KK", "LL", "MM", "NN", "OO", "PP", "QQ", "RR", "SS", "TT", "UU", "VV", "WW", "XX", "YY", "ZZ"];

fn add_values(
  values_: RwSignal<Vec<String>>,
  new_values: Vec<String>
) {
  let mut all_values = std::collections::BTreeSet::<String>::new();
  values_.with(|current_values| { current_values.iter().for_each(|value| { all_values.insert(value.to_owned()); } ) });
  new_values.iter().for_each(|value| { all_values.insert(value.to_owned()); } );
  values_.set(all_values.iter().map(|value| value.to_owned()).collect());
  log!("{:?}", values_.get());
}

#[component]
pub fn ValuesList(cx: Scope) -> impl IntoView {
  let values_ = create_rw_signal(cx, Vec::new());

  let mut i = 17;

  let feed_values = move |_| {
    let mut values = Vec::new();
    for _ in 0..3 {
      let index = i % VALUES.len();
      values.push(VALUES.get(index).unwrap().to_string());
      i = i.wrapping_mul(i); // very basic random generator
    }

    log!("{:?}", values);

    add_values(values_, values);
  };

  view! { cx,
    <button on:click=feed_values>"Add values"</button>
    <For
      each=move || values_.get()
      key=|value| value.to_owned()
      view=move |cx, value| {
        view! { cx,
          <div>{value}</div>
        }
      }
    />
  }
}

fn main() {
    mount_to_body(|cx| view! { cx, <ValuesList/> })
}

Clicking on "Add values" adds three random values that it adds to the list in alphabetical order, not keeping duplicates. After clicking a few times, I get the out of bounds panick mesage. I initially used the random crate instead of wrapping multiplications, but I was afraid the issue could come from there, plus it made the issue harder to debug as I never knew when I'd encounter the error.

So my question regarding this is: what am I doing wrong and how should I tackle this problem ? I guess I could use static loops, but my end goal is to have a somewhat sparsely populated (and big) bidimensional table so redrawing the whole table everytime seems a bit heavy handed and bad for performances.

Subsidiary question that might be more related to web assembly, I noticed that when panicking, sometimes the drop() method does not seem to be called. In particular, I had a mutex that was not poisoned, and instead complained that you cannot lock recursively the next time I tried to lock it.

I'm using nightly Rust and leptos 0.4.1.

[Schwartzmorn]

I have tried starting from scratch using trunks instead of cargo-leptos and switched to rust stable after noticing the behaviour of my code in codesandbox.io was not the same.

I updated the code snippet in my original message with the whole main.rs. I no longer see the index out of bounds error, but I'm still as confused by what is happening. After clicking on the "Add values" button, the vec has the value ["BB", "DD", "FF", "HH", "JJ", "LL", "NN", "PP", "RR", "TT", "VV", "XX", "ZZ"], but the page displays ["DD", "FF", "JJ", "HH", "RR", "XX", "NN", "VV"]. Is using a string as a key with wrong ?

[gbj]

Sorry I didn't see this over the weekend. It is very possible this is a bug in <For/>. Could you open an issue with the reproduction so we can keep track of it, please?

[Schwartzmorn]

I opened the issue #1297