Update from Gradle 6.9 to Gradle 8.0 (#168)

* Bump Gradle Wrapper to Gradle 8.0 (from 6.9)

* Remove outdated DSL: kotlinDslPluginOptions.experimentalWarning

> Configure project :buildSrc
e: P:\projects\contrib\github-nexus-publish-plugin\buildSrc\build.gradle.kts:14:5: Unresolved reference: experimentalWarning

> Configure project :buildSrc
The KotlinDslPluginOptions.experimentalWarning property has been deprecated. This is scheduled to be removed in Gradle 8.0. Flag has no effect since `kotlin-dsl` no longer relies on experimental features.
        at Build_gradle$3.execute(build.gradle.kts:14)
        (Run with --stacktrace to get the full stack trace of this deprecation warning.)

* Update Shadow plugin, because 6.1.0 is not compatible with Gradle 7.x and Gradle 8.x

* What went wrong:
org/gradle/api/plugins/MavenPlugin

* Try:
> Run with --info or --debug option to get more log output.

* Exception is:
java.lang.NoClassDefFoundError: org/gradle/api/plugins/MavenPlugin
        at com.github.jengelman.gradle.plugins.shadow.ShadowJavaPlugin$1.execute(ShadowJavaPlugin.groovy:101)

* Regenerate Gradle Wrapper with Gradle 8.0

* Bump Versions plugin, Gradle 7.x support is full-blown from 0.43.0

Gradle 7.4 fixes:
https://github.com/ben-manes/gradle-versions-plugin/releases/tag/v0.42.0

Gradle 7 required:
https://github.com/ben-manes/gradle-versions-plugin/releases/tag/v0.43.0

* Bump plugin-publish plugin to 1.x

pluginBundle was deprecated in Gradle 7.6 and removed in Gradle 8.0:
https://plugins.gradle.org/plugin/com.gradle.plugin-publish/1.0.0

maven-publish is auto-applied

* Lock in Java compilation version to the same as Kotlin, otherwise things can go wrong.

> Task :compileKotlin FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileKotlin'.
> 'compileJava' task (current target is 11) and 'compileKotlin' task (current target is 1.8) jvm target compatibility should be set to the same Java version.
  Consider using JVM toolchain: https://kotl.in/gradle/jvm/toolchain

* ConfigureUtil is deprecated in Gradle 7.1 and started nagging in Gradle 7.6. Building with Gradle 8.0 will obviously also warn. Let's suppress it for now, this will be dealt with in #152

* Add support for Spotless on Windows

Also in #167, but it's annoying not being able to get a green build locally.

* Move sourceCompatibility to the existing java block

* Keep building Kotlin with 1.3 compatibility, otherwise there are failures on older Gradle versions.

For example: NexusPublishPluginTests.should close staging repository
```
> Task :closeSonatypeStagingRepository FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':closeSonatypeStagingRepository'.
> kotlin.jvm.internal.PropertyReference1Impl.<init>(Ljava/lang/Class;Ljava/lang/String;Ljava/lang/String;I)V
```

* Silence unnecessary build warnings.

> Task :compileKotlin
w: API version 1.3 is deprecated and its support will be removed in a future version of Kotlin

> Task :compileTestKotlin
w: API version 1.3 is deprecated and its support will be removed in a future version of Kotlin

> Task :compileCompatTestKotlin
w: API version 1.3 is deprecated and its support will be removed in a future version of Kotlin

* Remove duplicate calls to withSourcesJar

It's done by the plugin-publish plugin too.
In the Gradle Metadata (.module) it duplicates artifacts if called multiple times.

* Remove unnecessary shadowed configuration

There is built-in support for standard configuration in plugin-publish and shadow plugins.

* Remove unidentified workaround

It doesn't change anything in the output publishToMavenLocal, it was probably for an older combination of Gradle / plugin-publish / shadow plugins.

* Work around unnecessary ClassPath in MANIFEST.MF

* Downgrade language version from Kotlin 1.8 to Kotlin 1.3 to generate compatible @kotlin.Metadata in the .class files.

* Remove unrelated change.

* Diagnose #168 (comment)

* Revert "Diagnose #168 (comment)"

This reverts commit c14acc5.

* Mention Kotlin 1.3 #168 (comment)

* Reduce CI load, re #168 (comment)

* Diagnose #168 (comment)

* Revert "Diagnose #168 (comment)"

This reverts commit 8488741.

* Add sha256 to wrapper

build.gradle.kts

@@ -5,12 +5,11 @@ import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
 plugins {
     `kotlin-dsl`
-    `maven-publish`
-    id("com.gradle.plugin-publish") version "0.21.0"
+    id("com.gradle.plugin-publish") version "1.1.0"
     id("com.diffplug.spotless") version "6.0.0"
-    id("com.github.johnrengelman.shadow") version "6.1.0"
+    id("com.github.johnrengelman.shadow") version "7.1.2"
     id("org.jetbrains.gradle.plugin.idea-ext")
-    id("com.github.ben-manes.versions") version "0.39.0"
+    id("com.github.ben-manes.versions") version "0.45.0"
     id("org.ajoberstar.stutter") version "0.6.0"
 }
 
@@ -21,19 +20,17 @@ val readableName = "Nexus Publish Plugin"
 description = "Gradle Plugin for publishing to Nexus that automates creating, closing, and releasing staging repositories"
 val repoUrl = "https://github.com/gradle-nexus/publish-plugin"
 
-pluginBundle {
-    description = project.description
-    website = repoUrl
-    vcsUrl = repoUrl
-    tags = listOf("publishing", "maven", "nexus")
-}
-
+@Suppress("UnstableApiUsage") // Using this DSL is the only way on Gradle 8.0, could still change slightly in the future.
 gradlePlugin {
+    website.set(repoUrl)
+    vcsUrl.set(repoUrl)
     plugins {
         create("nexusPublish") {
             id = "io.github.gradle-nexus.publish-plugin"
             displayName = readableName
             implementationClass = "io.github.gradlenexus.publishplugin.NexusPublishPlugin"
+            description = project.description
+            tags.addAll("publishing", "maven", "nexus")
         }
     }
 }
@@ -68,21 +65,18 @@ idea {
     }
 }
 
-val shadowed by configurations.creating
 configurations {
-    compileOnly {
-        extendsFrom(shadowed)
-    }
     testImplementation {
-        extendsFrom(shadowed)
         exclude(group = "junit", module = "junit")
     }
+    // Workaround https://github.com/gradle/gradle/issues/23928
+    shadow.configure { afterEvaluate { this@configure.dependencies.remove(project.dependencies.gradleApi()) } }
 }
 
 dependencies {
-    shadowed("com.squareup.retrofit2:retrofit:2.9.0")
-    shadowed("com.squareup.retrofit2:converter-gson:2.9.0")
-    shadowed("net.jodah:failsafe:2.4.3")
+    implementation("com.squareup.retrofit2:retrofit:2.9.0")
+    implementation("com.squareup.retrofit2:converter-gson:2.9.0")
+    implementation("net.jodah:failsafe:2.4.3")
 
     testImplementation("org.junit.jupiter:junit-jupiter:5.8.1")
     testImplementation("com.github.tomakehurst:wiremock:2.27.2")
@@ -93,8 +87,8 @@ dependencies {
 }
 
 java {
-    withJavadocJar()
-    withSourcesJar()
+    sourceCompatibility = JavaVersion.VERSION_1_8
+    targetCompatibility = JavaVersion.VERSION_1_8
 }
 
 stutter {
@@ -141,21 +135,34 @@ sourceSets {
     }
 }
 
-kotlinDslPluginOptions {
-    experimentalWarning.set(false)
-}
-
 tasks {
-    withType<KotlinCompile>().configureEach {
-        kotlinOptions.jvmTarget = "1.8"
+    afterEvaluate {
+        // This needs to be in an afterEvaluate block,
+        // because otherwise KotlinDslCompilerPlugins would win, and override what we've set to Kotlin 1.8.
+        withType<KotlinCompile>().configureEach {
+            kotlinOptions.jvmTarget = JavaVersion.VERSION_1_8.toString()
+            // Supporting Gradle 5.0+ needs to use Kotlin 1.3.
+            // See https://docs.gradle.org/current/userguide/compatibility.html
+            kotlinOptions.apiVersion = "1.3"
+            // Theoretically we could use newer language version here,
+            // but sadly the @kotlin.Metadata created on the classes would be incompatible with Kotlin 1.3 consumers.
+            kotlinOptions.languageVersion = "1.3"
+            doFirst {
+                if (kotlinOptions.apiVersion == "1.3") {
+                    // Suppress "Language version 1.3 is deprecated and its support will be removed in a future version of Kotlin".
+                    kotlinOptions.freeCompilerArgs += "-Xsuppress-version-warnings"
+                } else {
+                    TODO("Remove -Xsuppress-version-warnings suppression, or change the condition to ${kotlinOptions.languageVersion}")
+                }
+            }
+        }
     }
     val relocateShadowJar by registering(ConfigureShadowRelocation::class) {
         target = shadowJar.get()
         prefix = "io.github.gradlenexus.publishplugin.shadow"
     }
     shadowJar {
         dependsOn(relocateShadowJar)
-        configurations = listOf(shadowed)
         exclude("META-INF/maven/**", "META-INF/proguard/**", "META-INF/*.kotlin_module")
         manifest {
             attributes["Implementation-Version"] = project.version
@@ -205,25 +212,6 @@ tasks {
     }
 }
 
-configurations {
-    configureEach {
-        outgoing {
-            val removed = artifacts.removeIf { it.classifier.isNullOrEmpty() }
-            if (removed) {
-                artifact(tasks.shadowJar) {
-                    classifier = ""
-                }
-            }
-        }
-    }
-    // used by plugin-publish plugin
-    archives {
-        outgoing {
-            artifact(tasks.named("sourcesJar"))
-        }
-    }
-}
-
 publishing {
     publications {
         afterEvaluate {

buildSrc/build.gradle.kts

@@ -9,7 +9,3 @@ repositories {
 dependencies {
     implementation("gradle.plugin.org.jetbrains.gradle.plugin.idea-ext:gradle-idea-ext:0.7")
 }
-
-kotlinDslPluginOptions {
-    experimentalWarning.set(false)
-}

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,7 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.9-bin.zip
+distributionSha256Sum=4159b938ec734a8388ce03f52aa8f3c7ed0d31f5438622545de4f83a89b79788
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.0-bin.zip
+networkTimeout=10000
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists