[Android] After upgrading to Gradle 8.x.x - Inconsistent JVM-target compatibility detected for tasks 'compileDebugJavaWithJavac' (1.8) and 'compileDebugKotlin' (21).

[tomekit]

With a help of a script I've managed to add a namespace for image_compression_flutter instead of modifying it manually: fluttercandies/flutter_image_compress@6266ba4

// Source: https://medium.com/@vortj/solving-namespace-errors-in-flutters-android-gradle-configuration-c2baa6262f8b
subprojects {
    afterEvaluate { project ->
        if (project.hasProperty('android')) {
            project.android {
                if (namespace == null) {
                    namespace = project.group.toString()  // Set namespace as fallback
                }
                project.tasks.whenTaskAdded { task ->
                    if (task.name.contains('processDebugManifest') || task.name.contains('processReleaseManifest')) {
                        task.doFirst {
                            File manifestFile = file("${projectDir}/src/main/AndroidManifest.xml")
                            if (manifestFile.exists()) {
                                String manifestContent = manifestFile.text
                                if (manifestContent.contains('package=')) {
                                    manifestContent = manifestContent.replaceAll(/package="[^"]*"/, "")
                                    manifestFile.write(manifestContent)
                                    println "Removed 'package' attribute from ${manifestFile}"
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}

Unfortunately now I am getting:

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':image_compression_flutter:compileDebugKotlin'.
> Inconsistent JVM-target compatibility detected for tasks 'compileDebugJavaWithJavac' (1.8) and 'compileDebugKotlin' (21).

  Consider using JVM Toolchain: https://kotl.in/gradle/jvm/toolchain
  Learn more about JVM-target validation: https://kotl.in/gradle/jvm/target-validation 

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.
> Get more help at https://help.gradle.org.

BUILD FAILED in 51s
Error: Gradle task assembleDebug failed with exit code 1

Not entirely sure why this issue is being thrown, as my project uses consistent JVM versions:

compileOptions {
        coreLibraryDesugaringEnabled true

        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = '1.8'
    }

and these settings doesn't seem to be present in:

.pub-cache/hosted/pub.dev/image_compression_flutter-1.0.4/android/build.gradle

[zhengguo07q]

我也遇到了，兄弟解决了吗？

[tomekit]

It seems that applying this: https://stackoverflow.com/a/77861041/2263395 seem to at least avoid this build error, however I am not sure about the consequences behind the:

kotlin.jvm.target.validation.mode = IGNORE