fix(build): Strip MethodParameters so AGP 8.0 and older can dex the SDK

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Fixes
 
+- Fix a D8 crash (`NullPointerException: Cannot invoke "String.length()"`) when dexing the SDK with AGP 8.0 and older, a regression from 8.61.1 ([#6356](https://github.com/getsentry/sentry-java/pull/6356))
 - Always remove the first-draw listener after the first frame, even if no layout pass follows it ([#6152](https://github.com/getsentry/sentry-java/pull/6152))
 
 ## 8.61.1

build-logic/build.gradle.kts

@@ -5,6 +5,7 @@ plugins {
 dependencies {
   implementation(libs.animalsniffer.gradle.plugin)
   implementation(libs.spotlessLib)
+  implementation(libs.asm)
   compileOnly(libs.kotlin.gradle.plugin)
   compileOnly(libs.android.gradle.plugin)
 }

build-logic/src/main/kotlin/io/sentry/gradle/JdkTargetConvention.kt

@@ -27,6 +27,7 @@ private val PUBLISHED_JAVA_VERSION = JavaVersion.VERSION_1_8
  * - sample apps target the build JDK (21)
  * - unit test code will target the build JDK (21) (required for Mockito 5)
  * - published JVM modules main code pins the Java 1.8 release, for Java and for Kotlin
+ * - published modules Java code drops the MethodParameters attribute javac 21 adds
  * - published Android modules main code targets Java 1.8
  * - minSdk is set for Android libraries
  */
@@ -39,6 +40,10 @@ class JdkTargetConvention : Plugin<Project> {
     }
 
     project.plugins.withId("com.vanniktech.maven.publish") {
+      // Published Java classes must stay dexable by older D8 versions, see StripMethodParameters
+      project.tasks.withType(JavaCompile::class.java).configureEach {
+        doLast(StripMethodParameters())
+      }
       // Only works for non-android modules
       // See https://issuetracker.google.com/issues/278800528
       project.plugins.withId("java-library") {

build-logic/src/main/kotlin/io/sentry/gradle/StripMethodParameters.kt

@@ -0,0 +1,63 @@
+package io.sentry.gradle
+
+import org.gradle.api.Action
+import org.gradle.api.Task
+import org.gradle.api.tasks.compile.JavaCompile
+import org.objectweb.asm.ClassReader
+import org.objectweb.asm.ClassVisitor
+import org.objectweb.asm.ClassWriter
+import org.objectweb.asm.MethodVisitor
+import org.objectweb.asm.Opcodes
+
+/**
+ * Removes the
+ * [MethodParameters](https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.24)
+ * attribute from the classes a JavaCompile task produced.
+ *
+ * Since JDK 21 (JDK-8292275) javac writes MethodParameters for every method with synthetic or
+ * mandated parameters, e.g. bridge methods, even without `-parameters`. Those entries carry flags
+ * but no name, and the D8 of AGP 8.0 and older fails the build while dexing. See the
+ * [R8 fix](https://r8.googlesource.com/r8/+/9da58a26e22f195d8187492fac350a90e3315e92) for more
+ * details. An alternative would be adding the `-parameters` compile flag, but this could lead to
+ * other binary incompatibility issues along the road.
+ *
+ * The action removes every MethodParameters entry, also the named ones that `-parameters` writes.
+ * Keep it away from code that compiles with `-parameters`, e.g. the Spring Boot samples, where
+ * Spring resolves bean and handler parameters by name at runtime.
+ */
+internal class StripMethodParameters : Action<Task> {
+  override fun execute(task: Task) {
+    val classesDir = (task as JavaCompile).destinationDirectory.get().asFile
+    classesDir
+      .walkTopDown()
+      .filter { it.isFile && it.extension == "class" }
+      .forEach { file ->
+        val reader = ClassReader(file.readBytes())
+        val writer = ClassWriter(reader, 0)
+        val stripper = MethodParametersStripper(writer)
+        reader.accept(stripper, 0)
+        if (stripper.stripped) {
+          file.writeBytes(writer.toByteArray())
+        }
+      }
+  }
+
+  private class MethodParametersStripper(next: ClassVisitor) : ClassVisitor(Opcodes.ASM9, next) {
+    var stripped = false
+
+    override fun visitMethod(
+      access: Int,
+      name: String?,
+      descriptor: String?,
+      signature: String?,
+      exceptions: Array<out String>?,
+    ): MethodVisitor? {
+      val next = super.visitMethod(access, name, descriptor, signature, exceptions)
+      return object : MethodVisitor(Opcodes.ASM9, next) {
+        override fun visitParameter(name: String?, access: Int) {
+          stripped = true
+        }
+      }
+    }
+  }
+}

gradle/libs.versions.toml

@@ -157,6 +157,7 @@ lottie-compose = { module = "com.airbnb.android:lottie-compose", version = "6.7.
 logback-classic = { module = "ch.qos.logback:logback-classic", version.ref = "logback" }
 kotlin-gradle-plugin = { module = "org.jetbrains.kotlin:kotlin-gradle-plugin", version.ref = "kotlin" }
 android-gradle-plugin = { module = "com.android.tools.build:gradle", version.ref = "agp" }
+asm = { module = "org.ow2.asm:asm", version = "9.9" }
 nopen-annotations = { module = "com.jakewharton.nopen:nopen-annotations", version.ref = "nopen" }
 nopen-checker = { module = "com.jakewharton.nopen:nopen-checker", version.ref = "nopen" }
 nullaway = { module = "com.uber.nullaway:nullaway", version = "0.14.2" }