Nullable MutableLiveData gives an error when set to null [169249668]

Fixed

Bug

Status Update

No update yet.

Description

sp...@gmail.com

created issue #1

Sep 24, 2020 01:40PM

Component used:

implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version"
implementation "androidx.lifecycle:lifecycle-runtime-ktx:$lifecycle_version"
implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"

Version used: 2.2.0 and 2.3.0-alpha07

Devices/Android versions reproduced on: N/A

ViewModels with more than one MutableLiveData get their nullability wrong.

Example:

class ExampleViewModel : ViewModel() {

    val data1 = MutableLiveData<Int>()

    val data2 = MutableLiveData<Int?>()

    fun funct() {
        data1.value = 1
        data2.value = null
    }
}

This gives the error Error: Cannot set non-nullable LiveData value to null [NullSafeMutableLiveData]

Comments

sp...@gmail.com <sp...@gmail.com> #2Sep 24, 2020 01:41PM

Changing val data1 = MutableLiveData<Int>() to val data1 = MutableLiveData<Int?>() fixes this error, BTW.

se...@google.com <se...@google.com> Sep 24, 2020 02:43PM

Reassigned to jb...@google.com.

la...@gmail.com <la...@gmail.com> #3Jan 5, 2021 05:33AM

This bit me today and I was about to submit a bug but seems like it is in the queue. Given I already did the work, I figured I would share a sample git repo w/ the problem https://github.com/lance0428/NullLiveDataLinterIssue. I verified this is still an issue w/ 2.3.0-rc01.

Workarounds I have found:

turn off or reduce severity of NullSafeMutableLiveData in

build.gradle

android {
  ...
  lintOptions {
    // Turns off checks for the issue IDs you specify.
    disable 'NullSafeMutableLiveData'
  }
}

or lint.xml in root dir

<?xml version="1.0" encoding="UTF-8"?>
<lint>
    <issue id="NullSafeMutableLiveData" severity="warning" />
</lint>

Do the work for MutableLiveData encapsulation via backing properties dance (which really hurts my eyes).

class ExampleViewModel : ViewModel() {

    private val _data1 = MutableLiveData<Int>()
    val data1: LiveData<Int> = _data1

    private val _data2 = MutableLiveData<Int?>()
    val data2: LiveData<Int?> = _data2

    fun funct() {
        _data1.value = 1
        _data2.value = null
    }
}

ma...@gmail.com <ma...@gmail.com> #4Mar 4, 2021 02:38PM

I can confirm this made to a "stable" version 2.3.0 despite being known in early alpha versions...

sp...@gmail.com <sp...@gmail.com> #5Mar 4, 2021 02:57PM

It already existed in 2.2.0.

[Deleted User] <[Deleted User]> #6Mar 9, 2021 02:45PM

For me, this started to happen when I updated the libs to 2.3.0. If I downgrade them to 2.2.0, the error disappears.

ap...@google.com <ap...@google.com> #7Mar 11, 2021 07:06PM

Project: platform/frameworks/support
Branch: androidx-main

commit d5adf6168357145df07976060f0ae88dfdb05fe8
Author: Jeremy Woods <jbwoods@google.com>
Date: Mon Mar 08 14:17:49 2021

Fix MutableLiveData lint rule false report

If using multiple MutableLiveData variables as fields and mixed the
nullability, the lint rule could falsely report that a livedata value
was improperly being made null. This is because as constructed, it
didn't match up the fields with the assignments.

This change maps the field variable names to the reference types to
ensure that when reporting, the rule knows how to match them.

This also cleans up the rule by changing it to using a UastScanner.

Relnote: "The `NonNullableMutableLiveData` lint rule can now properly
differentiate between field variables with different nullability."
Test: added nullLiterallFailMultipleFieldsDifferent
Bug: 169249668

Change-Id: Ieb0270de1b22f3a10641643438bc2b9f1f5d72e8

M lifecycle/lifecycle-livedata-core-ktx-lint/src/main/java/androidx/lifecycle/lint/NonNullableMutableLiveDataDetector.kt
M lifecycle/lifecycle-livedata-core-ktx-lint/src/test/java/androidx/lifecycle/lint/NonNullableMutableLiveDataDetectorTest.kt

https://android-review.googlesource.com/1532131

jb...@google.com <jb...@google.com> #8Mar 11, 2021 10:23PM

This has been addressed internally and will be in the next lifecycle release.

You can follow the snapshot instructions using build id 7201697 with the lifecycle-livedata-core-ktx:2.4.0-SNAPSHOT dependency to verify.

sp...@gmail.com <sp...@gmail.com> #9Mar 11, 2021 11:23PM

Awesome! Thank you for fixing this.

jb...@google.com <jb...@google.com> Mar 11, 2021 11:46PM

Marked as fixed.

go...@gmail.com <go...@gmail.com> #10Apr 21, 2021 10:11PM

#FLHY

n....@tinkoff.ru <n....@tinkoff.ru> #11May 7, 2021 08:49AM

on 2.4.0-alpha01 androidx.lifecycle.lint.NonNullableMutableLiveDataDetector still doesn't work

Stack: ArrayIndexOutOfBoundsException:NonNullableMutableLiveDataDetector$createUastHandler$1.getFieldTypeReference(NonNullableMutableLiveDataDetector.kt:101)←NonNullableMutableLiveDataDetector$createUastHandler$1.visitClass(NonNullableMutableLiveDataDetector.kt:88)←UElementVisitor$DispatchPsiVisitor.visitClass(UElementVisitor.kt:602)←UElementVisitor$DelegatingPsiVisitor.visitClass(UElementVisitor.kt:1153)←AbstractKotlinUClass.accept(KotlinUClass.kt:63)←ImplementationUtilsKt.acceptList(implementationUtils.kt:23)←UFile$DefaultImpls.accept(UFile.kt:83)←KotlinUFile.accept(KotlinUFile.kt:30)

an...@gmail.com <an...@gmail.com> #12May 11, 2021 12:46PM

Please contact me

cu...@gmail.com <cu...@gmail.com> #13May 12, 2021 06:51AM

2.4.0-alpha01 still give error:

val currentUserId = MutableLiveData<String>()
fun setUserID(userId: String?) {
if (userId == null) {
return
}
val check: String = userId // no error
currentUserId.value = userId // error: Expected non-nullable value
}

cu...@gmail.com <cu...@gmail.com> #14May 12, 2021 07:19AM

It seems fixed in 2.4.0-SNAPSHOT

jo...@gmail.com <jo...@gmail.com> #15Jun 15, 2021 08:24PM

Is this fixed?

ya...@gmail.com <ya...@gmail.com> #16Jun 29, 2021 02:48PM

It still seems present in 2.4.0-alpha02:

Error: Cannot set non-nullable LiveData value to null [NullSafeMutableLiveData from jetified-lifecycle-livedata-core-ktx-2.4.0-alpha02

iv...@gmail.com <iv...@gmail.com> #17Jul 7, 2021 05:59PM

I've tested with the example above from: cu...@gmail.com<cu...@gmail.com> #13
There is a issue that is still happening on 2.4.0-alpha02 and in the snapshot version mentioned above.

js...@gmail.com <js...@gmail.com> #18Aug 12, 2021 05:18PM

What exactly is this thread context for and why am I the target on the command prompt etc

sp...@gmail.com <sp...@gmail.com> #19Aug 13, 2021 01:50PM

I think a new bug report should be created for comment #13. It's not the same issue as what I originally reported. The original issue is fixed and this issue should remain closed.

ad...@ade.se <ad...@ade.se> #20Sep 1, 2021 08:52AM

Here's a separate issue for the problem in comment #13

https://issuetracker.google.com/issues/198313895