SI-2464 Resiliance against missing InnerClass attributes

A classfile in the wild related to Vaadin lacked the InnerClasses
attribute. As such, our class file parser treated a nested enum
class as top-level, which led to a crash when trying to find its
linked module.

More details of the investigation are available in the JIRA comments.

The test introduces a new facility to rewrite classfiles.

This commit turns this situation into a logged warning, rather
than crashing. Code by @paulp, test by yours truly.

1 files changed, 31 insertions, 4 deletions

diff --git a/src/partest/scala/tools/partest/BytecodeTest.scala b/src/partest/scala/tools/partest/BytecodeTest.scala
index 2699083069..172fa29189 100644
--- a/src/partest/scala/tools/partest/BytecodeTest.scala
+++ b/src/partest/scala/tools/partest/BytecodeTest.scala
@@ -2,10 +2,9 @@ package scala.tools.partest
 
 import scala.tools.nsc.util.JavaClassPath
 import scala.collection.JavaConverters._
-import scala.tools.asm
-import asm.{ ClassReader }
-import asm.tree.{ClassNode, MethodNode, InsnList}
-import java.io.InputStream
+import scala.tools.asm.{ClassWriter, ClassReader}
+import scala.tools.asm.tree.{ClassNode, MethodNode, InsnList}
+import java.io.{FileOutputStream, FileInputStream, File => JFile, InputStream}
 import AsmNode._
 
 /**
@@ -127,3 +126,31 @@ abstract class BytecodeTest extends ASMConverters {
     new JavaClassPath(containers, DefaultJavaContext)
   }
 }
+
+object BytecodeTest {
+  /** Parse `file` as a class file, transforms the ASM representation with `f`,
+   *  and overwrites the orginal file.
+   */
+  def modifyClassFile(file: JFile)(f: ClassNode => ClassNode) {
+    val rfile = new reflect.io.File(file)
+    def readClass: ClassNode = {
+      val cr = new ClassReader(rfile.toByteArray())
+      val cn = new ClassNode()
+      cr.accept(cn, 0)
+      cn
+    }
+
+    def writeClass(cn: ClassNode) {
+      val writer = new ClassWriter(0)
+      cn.accept(writer)
+      val os = rfile.bufferedOutput()
+      try {
+        os.write(writer.toByteArray)
+      } finally {
+        os.close()
+      }
+    }
+
+    writeClass(f(readClass))
+  }
+}