Use Error Prone's @lazyinit annotation as a signal to upgrade referen…

…ce type fields to volatile semantics to avoid unsafe racy inits.

	Change on 2016/11/24 by kstanger <kstanger@google.com>

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=140129608

translator/src/main/java/com/google/devtools/j2objc/util/ElementUtil.java

@@ -46,7 +46,6 @@
 import javax.lang.model.element.ElementKind;
 import javax.lang.model.element.ExecutableElement;
 import javax.lang.model.element.Modifier;
-import javax.lang.model.element.Name;
 import javax.lang.model.element.NestingKind;
 import javax.lang.model.element.PackageElement;
 import javax.lang.model.element.TypeElement;
@@ -77,6 +76,8 @@ public final class ElementUtil {
   private static final Set<Modifier> VISIBILITY_MODIFIERS = EnumSet.of(
       Modifier.PUBLIC, Modifier.PROTECTED, Modifier.PRIVATE);
 
+  private static final String LAZY_INIT = "com.google.errorprone.annotations.concurrent.LazyInit";
+
   private final Elements javacElements;
 
   private static final Map<Integer, Set<Modifier>> modifierSets = new HashMap<>();
@@ -121,7 +122,11 @@ public static boolean isPrivate(Element element) {
   }
 
   public static boolean isVolatile(VariableElement element) {
-    return hasModifier(element, Modifier.VOLATILE);
+    return hasModifier(element, Modifier.VOLATILE)
+        // Upgrade reference type fields marked with error prone's LazyInit because this indicates
+        // an intentional racy init.
+        || (!element.asType().getKind().isPrimitive()
+            && hasQualifiedNamedAnnotation(element, LAZY_INIT));
   }
 
   public static boolean isTopLevel(TypeElement type) {
@@ -603,13 +608,7 @@ public static boolean isRuntimeAnnotation(Element e) {
   }
 
   public static AnnotationMirror getAnnotation(Element element, Class<?> annotationClass) {
-    for (AnnotationMirror annotation : element.getAnnotationMirrors()) {
-      String className = TypeUtil.getQualifiedName(annotation.getAnnotationType());
-      if (className.equals(annotationClass.getName())) {
-        return annotation;
-      }
-    }
-    return null;
+    return getQualifiedNamedAnnotation(element, annotationClass.getName());
   }
 
   public static boolean hasAnnotation(Element element, Class<?> annotationClass) {
@@ -619,16 +618,28 @@ public static boolean hasAnnotation(Element element, Class<?> annotationClass) {
   /**
    * Less strict version of the above where we don't care about the annotation's package.
    */
-  public static boolean hasNamedAnnotation(AnnotatedConstruct ac, String annotationName) {
+  public static boolean hasNamedAnnotation(AnnotatedConstruct ac, String name) {
     for (AnnotationMirror annotation : ac.getAnnotationMirrors()) {
-      Name annotationTypeName = annotation.getAnnotationType().asElement().getSimpleName();
-      if (annotationTypeName.toString().equals(annotationName)) {
+      if (getName(annotation.getAnnotationType().asElement()).equals(name)) {
         return true;
       }
     }
     return false;
   }
 
+  public static boolean hasQualifiedNamedAnnotation(Element element, String name) {
+    return getQualifiedNamedAnnotation(element, name) != null;
+  }
+
+  public static AnnotationMirror getQualifiedNamedAnnotation(Element element, String name) {
+    for (AnnotationMirror annotation : element.getAnnotationMirrors()) {
+      if (getQualifiedName((TypeElement) annotation.getAnnotationType().asElement()).equals(name)) {
+        return annotation;
+      }
+    }
+    return null;
+  }
+
   /**
    * Return true if a binding has a named "Nullable" annotation. Package names aren't
    * checked because different nullable annotations are defined by several different

translator/src/test/java/com/google/devtools/j2objc/translate/OperatorRewriterTest.java

@@ -201,4 +201,19 @@ public void testRetainedLocalRef() throws IOException {
         "return [((id<JavaUtilComparator>) nil_chk(((Test_Thing *) nil_chk(thing))->comp_)) "
           + "compareWithId:s1 withId:s2] == 0;");
   }
+
+  public void testLazyInitFields() throws IOException {
+    addSourcesToSourcepaths();
+    addSourceFile("package com.google.errorprone.annotations.concurrent;"
+        + "public @interface LazyInit {}",
+        "com/google/errorprone/annotations/concurrent/LazyInit.java");
+    String translation = translateSourceFile(
+        "import com.google.errorprone.annotations.concurrent.LazyInit;"
+        + "class Test { @LazyInit String lazyStr; @LazyInit static String lazyStaticStr; }",
+        "Test", "Test.h");
+    assertTranslation(translation, "volatile_id lazyStr_;");
+    assertTranslatedLines(translation,
+        "FOUNDATION_EXPORT volatile_id Test_lazyStaticStr;",
+        "J2OBJC_STATIC_FIELD_OBJ_VOLATILE(Test, lazyStaticStr, NSString *)");
+  }
 }