NullSafeMutableLiveData lint doesn't work when field have modifiers [183696616]

Fixed

Bug

Status Update

No update yet.

Description

ma...@gmail.com

created issue #1

Mar 25, 2021 02:14PM

Component used:
Version used: 2.3.1

```
class MyClass {
internal val liveDataField = MutableLiveData<Boolean>()

fun foo() {
liveDataField.value = false
liveDataField.value = null
}
}
```

Comments

se...@google.com <se...@google.com> Mar 25, 2021 02:23PM

Reassigned to jb...@google.com.

ma...@gmail.com <ma...@gmail.com> #2Mar 25, 2021 03:17PM

Still crashing with Compose 1.7.4.
I also tried moving sharedElement to BoxWithConstraints (rather than in its content), but did not help.
So the layout hierarchy looks like this (with more details and with "..." I replaced series of "normal" layouts):
NavHost -> ... -> AnimatedVisibility -> ... -> BoxWithConstraints with sharedElement -> some content
\> ... -> AnimatedVisibility -> ... -> LazyList -> ... -> Animated Visibility -> Selection container -> BoxWithConstraints with sharedElement -> some content

Any ideas?

ap...@google.com <ap...@google.com> #3Mar 30, 2021 10:47AM

Marked as fixed.

In your BoxWithConstraints do you do any conditional composition? Things like:

if (constraintsExceedsCertainThreshold) composeSomeContent() else someOtherContent()

mi...@gmail.com <mi...@gmail.com> #4Apr 2, 2021 03:28AM

No, it's just a `Text` which has different style depending on constraints.
Also note `sharedElement` is put on `BoxWithContraints` now, not on the content.
Thanks!

mi...@gmail.com <mi...@gmail.com> #5Apr 12, 2021 10:58PM

Based on the stacktrace, it seems like the item in question is composed but never placed. Do you use custom precompose or prefetch logic in your lazy list?

mi...@gmail.com <mi...@gmail.com> #6Jun 2, 2021 02:24AM

No, nothing custom. Just the default prefetch logic.
There is also one `AnimatedContent` above the `BoxWithConstraints`. Could this cause issues?
Thank you for looking into this.

ja...@gmail.com <ja...@gmail.com> #7Feb 23, 2022 05:25AM

The AnimatedContent never skips measuring/placing children after it composes them. So I don't expect that to be the issue.

Since you mentioned the modifier is on BoxWithConstraints rather than on the children of BoxWithConstraints, my guess is it's most likely related to LazyList.

Can you clarify what type of LazyList you are using? Is it LazyColumn/Row or LazyGrid, or something else?

c0...@gmail.com <c0...@gmail.com> #8May 16, 2022 03:50AM

Makes sense, thanks.
It's a LazyColumn.

c0...@gmail.com <c0...@gmail.com> #9May 16, 2022 03:52AM

One interesting observation is that this stack trace did not seem to come from the ComposeView with our app's Activity content. Because I did a release with copy pasted setContent + ComposeView subclass that is catching exceptions in dispatchDraw and it did not catch this crash. Is the animations framework doing content composition outside the app's composition context? One note: at the time I tried this exception catching, sharedElement was applied to the content of BoxWithConstraints (rather than to the BoxWithConstraints itself), but I don't think this would have caused the exception catching not to work.