Bootstrap plugin can not be used with the latest Gradle v6.5.x

[yuri-sergiichuk]

If one uses e.g. Gradle v6.5.1 with the latest Bootstrap v1.5.24 plugin, the following compilation error is raised:

java.lang.ClassFormatError: Duplicate method name "$deserializeLambda$" with signature "(Ljava.lang.invoke.SerializedLambda;)Ljava.lang.Object;" in class file io/spine/tools/gradle
/protoc/ProtobufGenerator
        at io.spine.tools.gradle.bootstrap.Extension$Builder.setProject(Extension.java:290)
        at io.spine.tools.gradle.bootstrap.BootstrapPlugin.applyExtension(BootstrapPlugin.java:80)
        at io.spine.tools.gradle.bootstrap.BootstrapPlugin.apply(BootstrapPlugin.java:69)
        at io.spine.tools.gradle.bootstrap.BootstrapPlugin.apply(BootstrapPlugin.java:64)
        at org.gradle.api.internal.plugins.ImperativeOnlyPluginTarget.applyImperative(ImperativeOnlyPluginTarget.java:43)
        at org.gradle.api.internal.plugins.RuleBasedPluginTarget.applyImperative(RuleBasedPluginTarget.java:51)
        at org.gradle.api.internal.plugins.DefaultPluginManager.addPlugin(DefaultPluginManager.java:181)
        at org.gradle.api.internal.plugins.DefaultPluginManager.access$300(DefaultPluginManager.java:51)
        at org.gradle.api.internal.plugins.DefaultPluginManager$AddPluginBuildOperation.run(DefaultPluginManager.java:276)

The issue is related to one raised by @dmdashenkov in the Gradle repository: gradle/gradle#13325. As Dmitry described in the issue, looks like Gradle instruments the code in some interesting way and most probably instruments it for Kotlin. We have an example project that works perfectly fine when the build configuration is done with Groovy.

As a possible solution, maybe we can try to fix the issue by using inner classes instead of lambdas.

[yuri-sergiichuk]

Gradle v6.6 is released. Please migrate to the new Gradle version to resolve the issue.