fix: normalize generated version metadata (#11651)

fix: normalize generated version metadata

Co-authored-by: brice.dutheil <brice.dutheil@datadoghq.com>

Author: bric3

buildSrc/src/main/kotlin/datadog/gradle/plugin/version/WriteVersionFilePlugin.kt

@@ -10,8 +10,17 @@ class WriteVersionFilePlugin : Plugin<Project> {
   override fun apply(target: Project) {
     target.pluginManager.apply("java")
 
+    val versionFileName = "${target.name}.version"
     val writeVersionFile = target.tasks.register<WriteVersionFile>("writeVersionNumberFile")
 
+    // Keep volatile generated version metadata from invalidating @Classpath consumers such as CodeNarc.
+    // https://docs.gradle.org/current/userguide/build_cache_concepts.html#runtime_classpath_normalization
+    target.normalization {
+      runtimeClasspath {
+        ignore(versionFileName)
+      }
+    }
+
     target.the<JavaPluginExtension>().sourceSets.named("main") {
       resources.srcDir(writeVersionFile)
     }

buildSrc/src/test/kotlin/datadog/gradle/plugin/version/WriteVersionFilePluginTest.kt

@@ -125,6 +125,65 @@ class WriteVersionFilePluginTest : VersionPluginsFixture() {
     assertThat(versionFile).doesNotExist()
   }
 
+  @Test
+  fun `generated version file is ignored in runtime classpath normalization`() {
+    writeSettings(
+      """
+      rootProject.name = "my-lib"
+      """
+    )
+    writeRootProject(
+      """
+      import org.gradle.api.DefaultTask
+      import org.gradle.api.file.ConfigurableFileCollection
+      import org.gradle.api.file.RegularFileProperty
+      import org.gradle.api.tasks.Classpath
+      import org.gradle.api.tasks.InputFiles
+      import org.gradle.api.tasks.OutputFile
+      import org.gradle.api.tasks.TaskAction
+
+      plugins {
+        id("dd-trace-java.version-file")
+      }
+
+      version = "1.2.3"
+
+      tasks.named<datadog.gradle.plugin.version.WriteVersionFile>("writeVersionNumberFile") {
+        gitHash.set(providers.gradleProperty("gitHash").orElse("abc12345"))
+      }
+
+      abstract class ClasspathProbe : DefaultTask() {
+        @get:InputFiles
+        @get:Classpath
+        val classpath: ConfigurableFileCollection = project.objects.fileCollection()
+
+        @get:OutputFile
+        val outputFile: RegularFileProperty = project.objects.fileProperty()
+
+        @TaskAction
+        fun probe() {
+          outputFile.get().asFile.writeText("probed")
+        }
+      }
+
+      tasks.register<ClasspathProbe>("classpathProbe") {
+        dependsOn("processResources")
+        classpath.from(sourceSets.main.get().runtimeClasspath)
+        outputFile.set(layout.buildDirectory.file("classpath-probe/output.txt"))
+      }
+      """
+    )
+
+    assertThat(run("classpathProbe", "-PgitHash=abc12345").task(":classpathProbe")?.outcome)
+      .isEqualTo(TaskOutcome.SUCCESS)
+
+    val result = run("classpathProbe", "-PgitHash=def67890")
+
+    assertThat(generatedVersionFile).hasContent("1.2.3~def67890")
+    assertThat(result.task(":writeVersionNumberFile")?.outcome).isEqualTo(TaskOutcome.SUCCESS)
+    assertThat(result.task(":classpathProbe")?.outcome).isEqualTo(TaskOutcome.UP_TO_DATE)
+  }
+
   private fun assertVersionFile(
     expectedContentRegex: String,
     task: String = ":writeVersionNumberFile",