compose desktop run task throws NullPointerException with gradle 6.6 or 6.7

[jbluntz]

Steps to recreate

1. Open either multiplatform-template or desktop-template projects
2. Update gradle/wrapper/gradle-wrapper.properties to gradle 6.6, 6.6.1, or 6.7
3. Run :desktop:run

Error Log:

A problem occurred configuring project ':desktop'.
> Could not create task ':desktop:run'.
   > at index 0

* Exception is:
org.gradle.api.ProjectConfigurationException: A problem occurred configuring project ':desktop'.
Caused by: org.gradle.api.internal.tasks.DefaultTaskContainer$TaskCreationException: Could not create task ':desktop:run'.
Caused by: java.lang.NullPointerException: at index 0
	at com.google.common.collect.ObjectArrays.checkElementNotNull(ObjectArrays.java:225)
	at com.google.common.collect.ObjectArrays.checkElementsNotNull(ObjectArrays.java:215)
	at com.google.common.collect.ObjectArrays.checkElementsNotNull(ObjectArrays.java:209)
	at com.google.common.collect.ImmutableList.construct(ImmutableList.java:326)
	at com.google.common.collect.ImmutableList.copyOf(ImmutableList.java:243)
	at org.gradle.api.internal.file.collections.DefaultConfigurableFileCollection$UnresolvedItemsCollector.plus(DefaultConfigurableFileCollection.java:409)
	at org.gradle.api.internal.file.collections.DefaultConfigurableFileCollection.from(DefaultConfigurableFileCollection.java:191)
	at org.jetbrains.compose.desktop.application.internal.ConfigureApplicationKt$configureRunTask$1.invoke(configureApplication.kt:159)
	at org.jetbrains.compose.desktop.application.internal.ConfigureApplicationKt$configureRunTask$1.invoke(configureApplication.kt)
	at org.jetbrains.compose.desktop.application.internal.ConfigureApplicationKt$composeTask$$inlined$apply$lambda$3.execute(configureApplication.kt:186)
	at org.jetbrains.compose.desktop.application.internal.ConfigureApplicationKt$composeTask$$inlined$apply$lambda$3.execute(configureApplication.kt)

[eygraber]

I don't fully understand what app.mainJar is supposed to be doing so I wouldn't know what the best way to fix this is, but looking through the source, this seems to be the issue.

Starting from Gradle 6.0 DefaultConfigurableFileCollection.from will throw a NPE if there is a null element in the collection (ImmutableList.copyOf makes sure that elements aren't null).

app.mainJar is null, and is added to the collection. The next line calls from again (with app._fromFiles), and therefore throws an NPE, failing the build.

A possible fix is to replace cp.from(app.mainJar.orNull) with app.mainJar.orNull?.let(cp::from), but again, I'm not fully sure what that's supposed to be doing, so I'm not sure if that would break something else.

[ScottPierce]

Seeing this same problem

[AlexeyTsvetkov]

Fixed in 56da868

[okushnikov]

Please check the following ticket on YouTrack for follow-ups to this issue. GitHub issues will be closed in the coming weeks.