Fix offline instrumentation: provide class loader for correct frame c…

…omputation

The frame computation requires other classes to be loaded, but in offline instrumentation we process one class after another, so the order of files could affect the result.

reporter/src/com/intellij/rt/coverage/instrument/Instrumentator.java

@@ -24,6 +24,9 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.URLClassLoader;
 import java.util.List;
 
 /**
@@ -35,12 +38,28 @@ public class Instrumentator {
   private final List<File> myRoots;
   private final List<File> myOutputRoots;
   private final Filters myFilters;
-
+  /**
+   * This loader is provided to the instrumenter for correct frames computation in ClassWriterImpl.
+   */
+  private final ClassLoader myLoader;
 
   public Instrumentator(List<File> roots, List<File> outputRoots, Filters filters) {
     myRoots = roots;
     myOutputRoots = outputRoots;
     myFilters = filters;
+    myLoader = createClassLoader(roots);
+  }
+
+  private ClassLoader createClassLoader(List<File> roots) {
+    URL[] urls = new URL[roots.size()];
+    for (int i = 0; i < roots.size(); i++) {
+      try {
+        urls[i] = myRoots.get(i).toURI().toURL();
+      } catch (MalformedURLException e) {
+        throw new RuntimeException(e);
+      }
+    }
+    return new URLClassLoader(urls);
   }
 
   public void instrument(final boolean countHits) {
@@ -84,9 +103,7 @@ protected void visitFile(String packageName, File file) {
           final String className = packageName.isEmpty()
               ? classSimpleName
               : ClassNameUtil.convertToInternalName(packageName) + "/" + classSimpleName;
-          // This loader is not user actually, just need some not null loader
-          final ClassLoader loader = ClassLoader.getSystemClassLoader();
-          final byte[] transformed = myTransformer.transform(loader, className, null, null, bytes);
+          final byte[] transformed = myTransformer.transform(myLoader, className, null, null, bytes);
           if (transformed != null) {
             bytes = transformed;
           }