Add 'feature.shadow' convention plugin (#86)

Signed-off-by: Jendrik Johannes <jendrik.johannes@gmail.com>

CHANGELOG.md

@@ -6,6 +6,7 @@
 * update spotless-plugin-gradle to 7.0.2 (improves configuration cache compatibility)
 * update dependency-analysis-gradle-plugin to 2.7.0 (addresses Gradle deprecation)
 * add 'feature.legacy-classpath' convention plugin
+* add 'feature.shadow' convention plugin
 
 ## Version 0.3.0
 

build.gradle.kts

@@ -16,6 +16,7 @@ dependencies {
     implementation("com.google.protobuf:protobuf-gradle-plugin:0.9.4")
     implementation("com.gradle.publish:plugin-publish-plugin:1.3.0")
     implementation("com.gradle:develocity-gradle-plugin:3.19")
+    implementation("com.gradleup.shadow:shadow-gradle-plugin:8.3.5")
     implementation(
         "gradle.plugin.com.google.cloud.artifactregistry:artifactregistry-gradle-plugin:2.2.2"
     )

src/main/descriptions/org.hiero.gradle.feature.shadow.txt

@@ -0,0 +1 @@
+Conventions for 'com.gradleup.shadow' to be used to build a fat Jar of an application

src/main/kotlin/org.hiero.gradle.feature.shadow.gradle.kts

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: Apache-2.0
+import com.github.jengelman.gradle.plugins.shadow.internal.DefaultDependencyFilter
+import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
+
+plugins {
+    id("application")
+    id("com.gradleup.shadow")
+}
+
+tasks.withType<ShadowJar>().configureEach {
+    group = "shadow"
+    mergeServiceFiles()
+
+    manifest { attributes("Multi-Release" to "true") }
+
+    // There is an issue in the shadow plugin that it automatically accesses the
+    // files in 'runtimeClasspath' while Gradle is building the task graph.
+    // See: https://github.com/GradleUp/shadow/issues/882
+    dependencyFilter = NoResolveDependencyFilter()
+}
+
+class NoResolveDependencyFilter : DefaultDependencyFilter(project) {
+    override fun resolve(configuration: FileCollection): FileCollection {
+        return configuration
+    }
+}

src/test/kotlin/org/hiero/gradle/test/ShadowTest.kt

@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: Apache-2.0
+package org.hiero.gradle.test
+
+import org.assertj.core.api.Assertions.assertThat
+import org.gradle.testkit.runner.TaskOutcome
+import org.hiero.gradle.test.fixtures.GradleProject
+import org.junit.jupiter.api.Test
+
+class ShadowTest {
+
+    @Test
+    fun `can build a fatjar for an application`() {
+        val p = GradleProject().withMinimalStructure()
+        p.dependencyVersionsFile(
+            """
+            plugins {
+                id("org.hiero.gradle.base.lifecycle")
+                id("org.hiero.gradle.base.jpms-modules")
+            }
+            dependencies.constraints {
+                api("org.apache.commons:commons-lang3:3.14.0") { because("org.apache.commons.lang3") }
+            }
+            """
+                .trimIndent()
+        )
+        p.moduleInfoFile(
+            """
+            module org.hiero.product.module.a {
+                requires org.apache.commons.lang3;
+            }"""
+                .trimIndent()
+        )
+        p.moduleBuildFile(
+            """
+            plugins {
+                id("org.hiero.gradle.module.application")
+                id("org.hiero.gradle.feature.shadow")
+            }
+            application {
+                mainClass = "org.hiero.product.module.a.ModuleA"
+            }
+        """
+                .trimIndent()
+        )
+
+        val result = p.run("assemble")
+
+        assertThat(result.task(":module-a:shadowJar")?.outcome).isEqualTo(TaskOutcome.SUCCESS)
+    }
+}