Support diffing Kotlin metadata versions for classes

CHANGELOG.md

@@ -6,6 +6,7 @@
 **Added**
 - Add `--summary-only` flag.
 - Support diffing bytecode versions for classes.
+- Support diffing Kotlin metadata versions for classes.
 
 **Changed**
 - Replace `com.jakewharton.diffuse.io.Size` with `me.saket.bytesize.ByteSize` in the APIs.

formats/api/formats.api

@@ -221,6 +221,7 @@ public final class com/jakewharton/diffuse/format/Class {
 	public final fun getBytecodeVersion ()I
 	public final fun getDeclaredMembers ()Ljava/util/List;
 	public final fun getDescriptor-BeHrSHk ()Ljava/lang/String;
+	public final fun getKotlinMetadataVersion ()[I
 	public final fun getReferencedMembers ()Ljava/util/List;
 	public fun hashCode ()I
 	public static final fun parse (Lcom/jakewharton/diffuse/io/Input;)Lcom/jakewharton/diffuse/format/Class;

formats/src/main/kotlin/com/jakewharton/diffuse/format/Class.kt

@@ -2,6 +2,7 @@ package com.jakewharton.diffuse.format
 
 import com.jakewharton.diffuse.io.Input
 import java.util.Objects
+import org.objectweb.asm.AnnotationVisitor
 import org.objectweb.asm.ClassReader
 import org.objectweb.asm.ClassVisitor
 import org.objectweb.asm.FieldVisitor
@@ -13,18 +14,26 @@ class Class
 private constructor(
   val descriptor: TypeDescriptor,
   val bytecodeVersion: Int,
+  val kotlinMetadataVersion: IntArray,
   val declaredMembers: List<Member>,
   val referencedMembers: List<Member>,
 ) {
   override fun toString() = descriptor.toString()
 
   override fun hashCode() =
-    Objects.hash(descriptor, bytecodeVersion, declaredMembers, referencedMembers)
+    Objects.hash(
+      descriptor,
+      bytecodeVersion,
+      kotlinMetadataVersion.contentHashCode(),
+      declaredMembers,
+      referencedMembers,
+    )
 
   override fun equals(other: Any?) =
     other is Class &&
       descriptor == other.descriptor &&
       bytecodeVersion == other.bytecodeVersion &&
+      kotlinMetadataVersion.contentEquals(other.kotlinMetadataVersion) &&
       declaredMembers == other.declaredMembers &&
       referencedMembers == other.referencedMembers
 
@@ -42,6 +51,7 @@ private constructor(
       return Class(
         type,
         declaredVisitor.version,
+        declaredVisitor.kotlinMetadataVersion,
         declaredVisitor.members.sorted(),
         referencedVisitor.members.sorted(),
       )
@@ -52,6 +62,7 @@ private constructor(
 private class DeclaredMembersVisitor(val type: TypeDescriptor, val methodVisitor: MethodVisitor) :
   ClassVisitor(Opcodes.ASM9) {
   var version: Int = 0
+  var kotlinMetadataVersion = intArrayOf()
   val members = mutableListOf<Member>()
 
   override fun visit(
@@ -87,6 +98,28 @@ private class DeclaredMembersVisitor(val type: TypeDescriptor, val methodVisitor
     members += Field(type, name, TypeDescriptor(descriptor))
     return null
   }
+
+  override fun visitAnnotation(descriptor: String?, visible: Boolean): AnnotationVisitor? {
+    if (descriptor == "Lkotlin/Metadata;") {
+      return KotlinMetadataAnnotationVisitor { kotlinMetadataVersion = it }
+    }
+    return super.visitAnnotation(descriptor, visible)
+  }
+}
+
+/**
+ * Reads [Metadata.bytecodeVersion] directly via ASM's [AnnotationVisitor] instead of
+ * `kotlin.metadata.jvm.KotlinClassMetadata` to avoid overheads for parsing [Metadata.data1] and
+ * [Metadata.data2].
+ */
+private class KotlinMetadataAnnotationVisitor(
+  private val onMetadataVersionFound: (IntArray) -> Unit
+) : AnnotationVisitor(Opcodes.ASM9) {
+  override fun visit(name: String?, value: Any?) {
+    if (name == "mv" && value is IntArray) {
+      onMetadataVersionFound(value)
+    }
+  }
 }
 
 private class ReferencedMembersVisitor : MethodVisitor(Opcodes.ASM9) {

formats/src/test/kotlin/com/jakewharton/diffuse/format/ClassTest.kt

@@ -1,7 +1,10 @@
 package com.jakewharton.diffuse.format
 
+import assertk.all
 import assertk.assertThat
 import assertk.assertions.containsOnly
+import assertk.assertions.hasSize
+import assertk.assertions.index
 import assertk.assertions.isEqualTo
 import com.jakewharton.diffuse.format.Class.Companion.toClass
 import java.util.function.Function
@@ -17,6 +20,11 @@ class ClassTest {
 
     assertThat(clazz.descriptor).isEqualTo(type)
     assertThat(clazz.bytecodeVersion).isEqualTo(55) // Reflects the JVM target 11.
+    assertThat(clazz.kotlinMetadataVersion).all {
+      hasSize(3) // Like [2,4,0].
+      index(0).isEqualTo(2)
+      index(2).isEqualTo(0)
+    }
 
     val initMethod = Method(type, "<init>", emptyList(), TypeDescriptor("V"))
     val stringArrayDescriptor = TypeDescriptor("[Ljava/lang/String;")

reports/src/main/kotlin/com/jakewharton/diffuse/diff/JarsDiff.kt

@@ -22,6 +22,10 @@ internal class JarsDiff(
     componentDiff(oldJars, newJars) { jar ->
       jar.classes.map { "${it.descriptor}: ${it.bytecodeVersion}" }
     }
+  val kotlinMetadataVersions =
+    componentDiff(oldJars, newJars) { jar ->
+      jar.classes.map { "${it.descriptor}: ${it.kotlinMetadataVersion.joinToString(".")}" }
+    }
   val methods = componentDiff(oldJars, newJars) { it.members.filterIsInstance<Method>() }
   val declaredMethods =
     componentDiff(oldJars, newJars) { it.declaredMembers.filterIsInstance<Method>() }
@@ -33,7 +37,8 @@ internal class JarsDiff(
   val referencedFields =
     componentDiff(oldJars, newJars) { it.referencedMembers.filterIsInstance<Field>() }
 
-  val changed = bytecodeVersions.changed || methods.changed || fields.changed
+  val changed =
+    bytecodeVersions.changed || kotlinMetadataVersions.changed || methods.changed || fields.changed
 }
 
 internal fun JarsDiff.toSummaryTable(name: String) = diffuseTable {
@@ -76,6 +81,7 @@ internal fun JarsDiff.toDetailReport() = buildString {
   // TODO appendComponentDiff("STRINGS", strings)?
   appendComponentDiff("CLASSES", classes)
   appendComponentDiff("BYTECODE VERSIONS", bytecodeVersions)
+  appendComponentDiff("KOTLIN METADATA VERSIONS", kotlinMetadataVersions)
   appendComponentDiff("METHODS", methods)
   appendComponentDiff("FIELDS", fields)
 }