Reactivity update twice when bind array or object on a component.

[RyanK1m]

Describe the bug
I'm trying to use double bind to retrieve values from a component.
Bind simple value like integer, float, string works just fine. When the value inside of the component changes, a parent gets reactivity update from component only once.
But if I want to bind an array or object, I got two updates from values changes inside of the component.

Logs
NA

To Reproduce
REPL:
https://svelte.dev/repl/b0204a06a3f24ede8850017c8b20b998?version=3.17.1

1. Press Test1 button
2. updateCount1 should increase +1 but increases +2
3. Press Test2 button
4. updateCount1 should increase +1 and it increases +1

Expected behavior
Double bind should cause reactivity update only once.

Stacktraces
NA

Information about your Svelte project:

• Your browser and the version: Chrome Version 79.0.3945.117 (Official Build) (64-bit)

• Your operating system: OS X 10.14.6

• Svelte version 3.17.1

• Rollup

Severity
This could potentially cause problems for users who want to track more complex objects from their components.

Additional context
I'm trying to build a multi-value-selectable select component.
https://svelte.dev/repl/4ddae394dcf841a687c76f6a9e702c8e?version=3.17.1
But I get reactivity update twice, and this can cause additional network usage if I want to hook value change(In this cause list of selected values) with an API

[soullivaneuh]

I ran onto this issue too, causing double fetch request at each change.

You see the implement here: https://gitlab.com/nexylan/svelty/-/merge_requests/9

Seems related to #3075 and #3197. Is it a bug or a miss-usage? In that case, there is any documentation about this?

Does anybody have a workaround for this issue?

[damooo]

@soullivaneuh i ran into same. v3.16.4 works as expected for temporary solution

[silllli]

I encountered the same issue.

[ruslan-khomiak]

I have the same problem

[etnilo-indra]

I have the same problem at v3.23.0

[pwwang]

This is seemingly solved at v3.24.1. But when that object/array is the argument of a function, the reactivity runs twice again:

https://svelte.dev/repl/5b37ba40c8854d86a9dab9ace0b6b861?version=3.24.1

[ruslan-khomiak]

@Conduitry Are you going to fix this?

[antony]

@Conduitry Are you going to fix this?

This works as expected in 3.29.0 - please try against the current released version before bumping issues.

https://svelte.dev/repl/e4ef6be683d84ff4a84d8c2c04703806?version=3.29.0