Check Java class files version (#49)

martinbonnin · web-flow · commit 1e419ad4d33e · 2025-12-03T10:38:52.000+01:00
diff --git a/tapmoc-gradle-plugin/build.gradle.kts b/tapmoc-gradle-plugin/build.gradle.kts
@@ -50,6 +50,9 @@ dependencies {
   compileOnly(libs.gradle.api)
   implementation(libs.gratatouille.wiring.runtime)
   gratatouille(project(":tapmoc-tasks"))
+
+  testImplementation(gradleTestKit())
+  testImplementation(kotlin("test"))
 }
 
 gratatouille {
@@ -59,3 +62,14 @@ gratatouille {
   pluginLocalPublication("com.gradleup.tapmoc")
 }
 
+tasks.withType<Test>().configureEach {
+  dependsOn("publishAllPublicationsToLocalRepository")
+  dependsOn(":tapmoc-tasks:publishAllPublicationsToLocalRepository")
+}
+
+extensions.getByType<PublishingExtension>().repositories {
+  maven {
+    name = "local"
+    url = rootDir.resolve("build/m2").toURI()
+  }
+}
diff --git a/tapmoc-gradle-plugin/src/main/kotlin/tapmoc/internal/TapmocExtensionImpl.kt b/tapmoc-gradle-plugin/src/main/kotlin/tapmoc/internal/TapmocExtensionImpl.kt
@@ -2,22 +2,23 @@ package tapmoc.internal
 
 import org.gradle.api.DefaultTask
 import org.gradle.api.NamedDomainObjectSet
-import tapmoc.TapmocExtension
-import tapmoc.Severity
-import tapmoc.configureJavaCompatibility
-import tapmoc.configureKotlinCompatibility
-import tapmoc.task.registerCheckKotlinMetadataTask
 import org.gradle.api.Project
-import org.gradle.api.Task
 import org.gradle.api.artifacts.Configuration
 import org.gradle.api.artifacts.component.ModuleComponentIdentifier
 import org.gradle.api.attributes.Usage
 import org.gradle.api.provider.Provider
 import org.gradle.api.tasks.TaskProvider
+import tapmoc.Severity
+import tapmoc.TapmocExtension
+import tapmoc.configureJavaCompatibility
+import tapmoc.configureKotlinCompatibility
+import tapmoc.task.registerCheckJavaClassFilesVersionTask
+import tapmoc.task.registerCheckKotlinMetadataTask
 import tapmoc.task.registerCheckKotlinStdlibVersionsTask
 
 internal abstract class TapmocExtensionImpl(private val project: Project) : TapmocExtension {
   private var kotlinVersion: String? = null
+  private var javaVersion: Int? = null
   private var kotlinMetadataSeverity = Severity.ERROR
   private var kotlinStdlibSeverity = Severity.ERROR
 
@@ -28,6 +29,8 @@ internal abstract class TapmocExtensionImpl(private val project: Project) : Tapm
 
   init {
     val kotlinVersionProvider = project.provider { kotlinVersion ?: error("Tapmoc: please call Tapmoc::kotlin(version) to specify the target Kotlin version.") }
+    val javaVersionProvider = project.provider { javaVersion ?: error("Tapmoc: please call Tapmoc::java(version) to specify the target Java version.") }
+
     apiDependencies = project.configurations.register("tapmocApiDependencies") {
       it.isCanBeConsumed = false
       it.isCanBeResolved = true
@@ -66,9 +69,18 @@ internal abstract class TapmocExtensionImpl(private val project: Project) : Tapm
     )
     checkKotlinStdlib.configure { it.isEnabled = false }
     project.tasks.named("check").configure { it.dependsOn(checkKotlinStdlib) }
+
+    val checkJavaClassFilesVersionTask = project.registerCheckJavaClassFilesVersionTask(
+      taskName = "tapmocCheckJavaClassFilesVersion",
+      warningAsError = project.provider { kotlinStdlibSeverity == Severity.ERROR },
+      javaVersion = javaVersionProvider,
+      jarFiles = project.files(apiDependencies, runtimeDependencies)
+    )
+    project.tasks.named("check").configure { it.dependsOn(checkJavaClassFilesVersionTask) }
   }
 
   override fun java(version: Int) {
+    javaVersion = version
     project.configureJavaCompatibility(version)
   }
 
diff --git a/tapmoc-gradle-plugin/src/test/kotlin/Tests.kt b/tapmoc-gradle-plugin/src/test/kotlin/Tests.kt
@@ -0,0 +1,59 @@
+import java.io.File
+import java.util.Properties
+import kotlin.test.Test
+import org.gradle.testkit.runner.GradleRunner
+import org.junit.Assert.assertTrue
+
+class Tests {
+  @Test
+  fun wrongJavaBytecodeIsDetected() {
+    withTestProject("java") {
+      val result = GradleRunner.create()
+        .withProjectDir(it)
+        .withDebug(false)
+        .withArguments("build")
+        .forwardOutput()
+        .buildAndFail()
+
+      assertTrue(result.output.contains("targets class file version 55 (Java 11) which is newer than supported <= 52 (Java 8)."))
+    }
+  }
+
+  @Test
+  fun metaInfIsExcluded() {
+    withTestProject("java-meta-inf") {
+      GradleRunner.create()
+        .withProjectDir(it)
+        .withDebug(false)
+        .withArguments("build")
+        .forwardOutput()
+        .build()
+    }
+  }
+}
+
+
+
+private fun withTestProject(name: String, block: (File) -> Unit) {
+  val src = File("testProjects/$name")
+  val dst = File("build/testProject")
+  dst.deleteRecursively()
+
+  src.copyRecursively(dst)
+
+  dst.walk().onLeave {
+    if (it.isDirectory && it.name == "build") {
+      it.deleteRecursively()
+    }
+  }.count() // count is just used to collect the sequence
+
+  val currentVersion = Properties().apply {
+    File("../librarian.root.properties").reader().use {
+      load(it)
+    }
+  }
+  dst.resolve("build.gradle.kts").let {
+    it.writeText(it.readText().replace("PLACEHOLDER", currentVersion.get("pom.version").toString()))
+  }
+  block(dst)
+}
diff --git a/tapmoc-gradle-plugin/testProjects/java-meta-inf/build.gradle.kts b/tapmoc-gradle-plugin/testProjects/java-meta-inf/build.gradle.kts
@@ -0,0 +1,21 @@
+import tapmoc.Severity
+
+buildscript {
+  dependencies {
+    classpath("com.gradleup.tapmoc:tapmoc-gradle-plugin:PLACEHOLDER")
+  }
+}
+
+plugins {
+  id("java")
+}
+
+pluginManager.apply("com.gradleup.tapmoc")
+extensions.getByType(tapmoc.TapmocExtension::class.java).apply {
+  java(8)
+  checkDependencies(Severity.ERROR)
+}
+
+dependencies {
+  implementation("com.squareup.okhttp3:okhttp-jvm:5.3.2")
+}
diff --git a/tapmoc-gradle-plugin/testProjects/java-meta-inf/settings.gradle.kts b/tapmoc-gradle-plugin/testProjects/java-meta-inf/settings.gradle.kts
@@ -0,0 +1,6 @@
+pluginManagement {
+  listOf(repositories, dependencyResolutionManagement.repositories).forEach {
+    it.mavenCentral()
+    it.maven("../../../build/m2")
+  }
+}
diff --git a/tapmoc-gradle-plugin/testProjects/java/Hello.java b/tapmoc-gradle-plugin/testProjects/java/Hello.java
@@ -0,0 +1,5 @@
+package com.example;
+
+public class Hello {
+  public static String world = "Hello World";
+}
diff --git a/tapmoc-gradle-plugin/testProjects/java/build.gradle.kts b/tapmoc-gradle-plugin/testProjects/java/build.gradle.kts
@@ -0,0 +1,68 @@
+import javax.tools.DiagnosticCollector
+import javax.tools.JavaFileObject
+import javax.tools.StandardLocation
+import javax.tools.ToolProvider
+import tapmoc.Severity
+
+buildscript {
+  dependencies {
+    classpath("com.gradleup.tapmoc:tapmoc-gradle-plugin:PLACEHOLDER")
+  }
+}
+
+plugins {
+  id("java")
+}
+
+pluginManager.apply("com.gradleup.tapmoc")
+extensions.getByType(tapmoc.TapmocExtension::class.java).apply {
+  java(8)
+  kotlin("2.0.0") // This should be a no-op
+  checkDependencies(Severity.ERROR)
+}
+
+abstract class GenerateClasses: DefaultTask() {
+  @get:OutputDirectory
+  abstract val output: DirectoryProperty
+
+  @get:InputFile
+  abstract val source: RegularFileProperty
+
+  @TaskAction
+  fun taskAction() {
+    val javac = ToolProvider.getSystemJavaCompiler()
+    val diagnostics = DiagnosticCollector<JavaFileObject>()
+    javac.getStandardFileManager(diagnostics, null, null).use { fm ->
+      fm.setLocation(StandardLocation.CLASS_OUTPUT, listOf(output.get().asFile))
+
+      val javaSourceFiles = listOf(source.asFile.get())
+      val fileObjects = fm.getJavaFileObjectsFromFiles(javaSourceFiles)
+
+      val options = buildList {
+        add("--release")
+        add("11") // Compile using a higher version
+      }
+
+      val task = javac.getTask(null, fm, diagnostics, options, null, fileObjects)
+
+      val success = task.call()
+      if (!success) {
+        error("Java compilation failed.")
+      }
+    }
+  }
+}
+
+val generateClasses = tasks.register("javaClasses", GenerateClasses::class.java) {
+  output.set(file("build/javaClasses"))
+  source.set(file("Hello.java"))
+}
+
+val jar = tasks.register("javaJar", Jar::class.java) {
+  from(generateClasses)
+  archiveClassifier = "higher"
+}
+
+dependencies {
+  implementation(files(jar))
+}
diff --git a/tapmoc-gradle-plugin/testProjects/java/settings.gradle.kts b/tapmoc-gradle-plugin/testProjects/java/settings.gradle.kts
@@ -0,0 +1,6 @@
+pluginManagement {
+  listOf(repositories, dependencyResolutionManagement.repositories).forEach {
+    it.mavenCentral()
+    it.maven("../../../build/m2")
+  }
+}
diff --git a/tapmoc-gradle-plugin/testProjects/java/src/main/java/Main.java b/tapmoc-gradle-plugin/testProjects/java/src/main/java/Main.java
@@ -0,0 +1,14 @@
+import com.example.Hello;
+
+import java.util.ArrayList;
+public class Main {
+  public static void main(String[] args) {
+
+    ArrayList<String> list = new ArrayList<String>();
+    list.add("foo");
+    // This must fail to compile because it's not in JDK 11
+    // list.removeFirst();
+
+    System.out.println(Hello.world);
+  }
+}
diff --git a/tapmoc-tasks/api/tapmoc-tasks.api b/tapmoc-tasks/api/tapmoc-tasks.api
@@ -1,3 +1,13 @@
+public final class tapmoc/task/CheckJavaClassFilesVersionEntryPoint {
+	public static final field Companion Ltapmoc/task/CheckJavaClassFilesVersionEntryPoint$Companion;
+	public fun <init> ()V
+	public static final fun run (Ljava/util/function/BiConsumer;ZLjava/util/List;ILjava/io/File;)V
+}
+
+public final class tapmoc/task/CheckJavaClassFilesVersionEntryPoint$Companion {
+	public final fun run (Ljava/util/function/BiConsumer;ZLjava/util/List;ILjava/io/File;)V
+}
+
 public final class tapmoc/task/CheckKotlinMetadataEntryPoint {
 	public static final field Companion Ltapmoc/task/CheckKotlinMetadataEntryPoint$Companion;
 	public fun <init> ()V
diff --git a/tapmoc-tasks/build.gradle.kts b/tapmoc-tasks/build.gradle.kts
@@ -12,6 +12,7 @@ Librarian.module(project)
 
 dependencies {
   implementation(libs.kotlin.metadata)
+  implementation(libs.asm)
   implementation(libs.gratatouille.tasks.runtime)
 }
 
@@ -24,3 +25,10 @@ gratatouille {
     addDependencies.set(false)
   }
 }
+
+extensions.getByType<PublishingExtension>().repositories {
+  maven {
+    name = "local"
+    url = rootDir.resolve("build/m2").toURI()
+  }
+}
diff --git a/tapmoc-tasks/src/main/kotlin/tapmoc/task/checkJavaClassFilesVersion.kt b/tapmoc-tasks/src/main/kotlin/tapmoc/task/checkJavaClassFilesVersion.kt
@@ -0,0 +1,63 @@
+package tapmoc.task
+
+import gratatouille.tasks.GInputFiles
+import gratatouille.tasks.GLogger
+import gratatouille.tasks.GOutputFile
+import gratatouille.tasks.GTask
+import org.objectweb.asm.ClassReader
+import org.objectweb.asm.ClassVisitor
+import org.objectweb.asm.Opcodes
+import java.util.zip.ZipInputStream
+
+@GTask
+internal fun checkJavaClassFilesVersion(
+  logger: GLogger,
+  warningAsError: Boolean,
+  jarFiles: GInputFiles,
+  javaVersion: Int,
+  output: GOutputFile
+) {
+  val maxAllowedClassFileVersion = 44 + javaVersion
+
+  jarFiles.forEach { fileWithPath ->
+    ZipInputStream(fileWithPath.file.inputStream()).use { zis ->
+      var entry = zis.nextEntry
+      while (entry != null) {
+        if (!entry.isDirectory && entry.name.endsWith(".class", ignoreCase = true) && !entry.name.startsWith("META-INF/versions")) {
+          val classBytes = zis.readBytes()
+          val cr = ClassReader(classBytes)
+          var classFileVersion = -1
+
+          cr.accept(
+            object : ClassVisitor(Opcodes.ASM9) {
+              override fun visit(
+                version: Int,
+                access: Int,
+                name: String?,
+                signature: String?,
+                superName: String?,
+                interfaces: Array<out String>?
+              ) {
+                classFileVersion = version
+              }
+            },
+            ClassReader.SKIP_CODE or ClassReader.SKIP_DEBUG or ClassReader.SKIP_FRAMES
+          )
+
+          if (classFileVersion > maxAllowedClassFileVersion) {
+            val humanReadable = "class file version $classFileVersion (Java ${classFileVersion - 44})"
+            val expectedHuman = "<= $maxAllowedClassFileVersion (Java $javaVersion)"
+            logger.logOrFail(
+              warningAsError,
+              "${fileWithPath.file.path}:${entry.name} targets $humanReadable which is newer than supported $expectedHuman."
+            )
+          }
+        }
+        entry = zis.nextEntry
+      }
+    }
+  }
+
+  output.writeText("Nothing to see here, this file is just a marker that the task executed successfully.")
+}
+
diff --git a/tapmoc-tasks/src/main/kotlin/tapmoc/task/checkKotlinMetadata.kt b/tapmoc-tasks/src/main/kotlin/tapmoc/task/checkKotlinMetadata.kt
@@ -41,7 +41,7 @@ internal fun checkKotlinMetadata(
     fileWithPath.file.forEachModuleInfoFile { name, bytes ->
       val metadata = KotlinModuleMetadata.read(bytes)
       if (metadata.version > supportedVersion) {
-        logger.logOrFail(warningAsError, "w: ${fileWithPath.file.path}:$name contains unsupported metadata ${metadata.version} (expected: $kotlinVersion).  Use `./gradlew dependencies to investigate the dependency tree.")
+        logger.logOrFail(warningAsError, "${fileWithPath.file.path}:$name contains unsupported metadata ${metadata.version} (expected: $kotlinVersion).  Use `./gradlew dependencies to investigate the dependency tree.")
       }
     }
   }
@@ -65,7 +65,7 @@ internal fun GLogger.logOrFail(warningAsError: Boolean, message: String) {
   if (warningAsError) {
     kotlin.error(message)
   } else {
-    warn(message)
+    warn("w: $message")
   }
 }
 
