Each data is duplicated when using transitions in await syntax

[itsdonnix]

Describe the bug
I try to use transitions in each of my data ({#each}) that I get after my Promise resolves. But when I re-assign it to the variable that holds the Promise, the displayed data actually increases.

Discord link => https://discord.com/channels/457912077277855764/653341885674553345/791014063496101898

svelte-bug.mp4

Logs
Nothing shows in the console

To Reproduce
https://svelte.dev/repl/99c98342054542ca9c9a82f97c0f200c?version=3.31.0
https://github.com/donnisnoni/svelte-127253y6123-bug/blob/bug/src/views/admin/rayon/Index.svelte#L54-L75
https://github.com/donnisnoni/svelte-127253y6123-bug/blob/bug/src/store/rayon.js#L22-L34

Expected behavior
The data is not duplicated/increased

Information about my Svelte project:

  System:
    OS: Linux 5.10 Linux Mint 20 (Ulyana)
    CPU: (4) x64 Intel(R) Core(TM) i3-4005U CPU @ 1.70GHz
    Memory: 445.32 MB / 3.76 GB
    Container: Yes
    Shell: 3.1.2 - /usr/bin/fish
  Binaries:
    Node: 14.15.1 - ~/nvm/node/v14.15.1/bin/node
    Yarn: 1.22.10 - ~/nvm/node/v14.15.1/bin/yarn
    npm: 6.14.9 - ~/nvm/node/v14.15.1/bin/npm
  Browsers:
    Chrome: 87.0.4280.88
  npmPackages:
    svelte: ^3.31.0 => 3.31.0 
    vite: ^1.0.0-rc.13 => 1.0.0-rc.13 

Additional context
Add any other context about the problem here.

[mdynnl]

https://svelte.dev/repl/99c98342054542ca9c9a82f97c0f200c?version=3.31.0

[mdynnl]

after playing around in the repl
i've known a few things

• #each doesn't cause this ( no #each in above repl )
• out transition does
  try changing transition:name to in:name(no issue) or out:name(this one does)

current behavior(to my understanding):

1. promise holding variable (#await promise) gets a new promise
2. outro starts and wait for the promise to be resolved
3. then node gets deleted after outro ends
4. promise resolves
5. a new node with changes comes in
6. intro starts and ends

why and when does duplication happen?
-> when the promise resolves before the outro ends

promise is usually fetching and doesn't resolve before outro ends
old node gets deleted meaning currentNode = undefined
then new node with promise result comes in, currentNode = newNode

but when it resolves before outro ends
new node comes in currentNode = newNode
and after that, old node gets deleted currentNode = undefined

so, when the promise holder gets a new promise
the outro never plays as currentNode = undefined
but after the promise resolves
new node comes in
old node doesn't get removed

i hope this makes sense to you and helps track the bug
pardon my poor writing and explaining skills

[Conduitry]

This is fixed in 3.31.2 - https://svelte.dev/repl/99c98342054542ca9c9a82f97c0f200c?version=3.31.2