Rename and implement emulated interfaces as needed during android desugaring

RELNOTES: None.

PiperOrigin-RevId: 186904092
GitOrigin-RevId: 30af177d5cd2188ee6e23ba849d865b8a42ad8f8
Change-Id: I6ba0cd552638f560bdbfef1ff308ba436a2de720

2 files changed, 68 insertions, 0 deletions

diff --git a/java/com/google/devtools/build/android/desugar/Desugar.java b/java/com/google/devtools/build/android/desugar/Desugar.java
index cd55655..eee8802 100644
--- a/java/com/google/devtools/build/android/desugar/Desugar.java
+++ b/java/com/google/devtools/build/android/desugar/Desugar.java
@@ -617,6 +617,7 @@ class Desugar {
       // Don't need a ClassReaderFactory b/c static interface methods should've been moved.
       ClassVisitor visitor = writer;
       if (coreLibrarySupport != null) {
+        visitor = new EmulatedInterfaceRewriter(visitor, coreLibrarySupport);
         visitor = new CorePackageRenamer(visitor, coreLibrarySupport);
         visitor = new CoreLibraryInvocationRewriter(visitor, coreLibrarySupport);
       }
@@ -669,6 +670,7 @@ class Desugar {
     ClassVisitor visitor = checkNotNull(writer);
 
     if (coreLibrarySupport != null) {
+      visitor = new EmulatedInterfaceRewriter(visitor, coreLibrarySupport);
       visitor = new CorePackageRenamer(visitor, coreLibrarySupport);
       visitor = new CoreLibraryInvocationRewriter(visitor, coreLibrarySupport);
     }
@@ -751,6 +753,7 @@ class Desugar {
     ClassVisitor visitor = checkNotNull(writer);
 
     if (coreLibrarySupport != null) {
+      visitor = new EmulatedInterfaceRewriter(visitor, coreLibrarySupport);
       visitor = new CorePackageRenamer(visitor, coreLibrarySupport);
       visitor = new CoreLibraryInvocationRewriter(visitor, coreLibrarySupport);
     }
diff --git a/java/com/google/devtools/build/android/desugar/EmulatedInterfaceRewriter.java b/java/com/google/devtools/build/android/desugar/EmulatedInterfaceRewriter.java
new file mode 100644
index 0000000..d3e786d
--- /dev/null
+++ b/java/com/google/devtools/build/android/desugar/EmulatedInterfaceRewriter.java
@@ -0,0 +1,65 @@
+// Copyright 2018 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package com.google.devtools.build.android.desugar;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.Opcodes;
+
+/**
+ * Visitor that renames emulated interfaces and marks classes that extend emulated interfaces to
+ * also implement the renamed interfaces.  {@link DefaultMethodClassFixer} makes sure the requisite
+ * methods are present.  Doing this helps with dynamic dispatch on emulated interfaces.
+ */
+public class EmulatedInterfaceRewriter extends ClassVisitor {
+
+  private final CoreLibrarySupport support;
+
+  public EmulatedInterfaceRewriter(ClassVisitor dest, CoreLibrarySupport support) {
+    super(Opcodes.ASM6, dest);
+    this.support = support;
+  }
+
+  @Override
+  public void visit(
+      int version,
+      int access,
+      String name,
+      String signature,
+      String superName,
+      String[] interfaces) {
+    boolean isEmulated = support.isEmulatedCoreClassOrInterface(name);
+    if (interfaces != null && interfaces.length > 0 && !isEmulated) {
+      // Make classes implementing emulated interfaces also implement the renamed interfaces we
+      // create below.
+      ArrayList<String> newInterfaces = new ArrayList<>(interfaces.length + 2);
+      Collections.addAll(newInterfaces, interfaces);
+      for (String itf : interfaces) {
+        if (support.isEmulatedCoreClassOrInterface(itf)) {
+          newInterfaces.add(support.renameCoreLibrary(itf));
+        }
+      }
+      if (interfaces.length != newInterfaces.size()) {
+        interfaces = newInterfaces.toArray(interfaces);
+        signature = null; // additional interfaces invalidate signature
+      }
+    }
+
+    if (BitFlags.isInterface(access) && isEmulated) {
+      name = support.renameCoreLibrary(name);
+    }
+    super.visit(version, access, name, signature, superName, interfaces);
+  }
+}