Apply @Nullable to fields in the generated class where appropriate.

We already did this if it was a `TYPE_USE` `@Nullable` or if the corresponding property method was annotated with `@CopyAnnotations`. Now we do it in every other case as well.

RELNOTES=If an AutoValue property method is `@Nullable`, the corresponding field in the generated class will be too. This was already the case for `TYPE_USE` `@Nullable` or if the method had `@CopyAnnotations`, but now `@Nullable` will be copied in other cases too.
PiperOrigin-RevId: 559765107

Author: eamonnmcmanus

value/src/main/java/com/google/auto/value/processor/AutoValueishProcessor.java

@@ -17,6 +17,7 @@
 
 import static com.google.auto.common.AnnotationMirrors.getAnnotationValue;
 import static com.google.auto.common.GeneratedAnnotations.generatedAnnotation;
+import static com.google.auto.common.MoreElements.asType;
 import static com.google.auto.common.MoreElements.getPackage;
 import static com.google.auto.common.MoreElements.isAnnotationPresent;
 import static com.google.auto.common.MoreStreams.toImmutableList;
@@ -1215,19 +1216,31 @@ final ImmutableListMultimap<ExecutableElement, AnnotationMirror> propertyFieldAn
 
   private ImmutableList<AnnotationMirror> propertyFieldAnnotations(
       TypeElement type, ExecutableElement method) {
+    // We need to exclude type annotations from the ones being output on the method, since
+    // they will be output as part of the field's type.
+    Set<String> returnTypeAnnotations =
+        getReturnTypeAnnotations(method, this::annotationAppliesToFields);
     if (!hasAnnotationMirror(method, COPY_ANNOTATIONS_NAME)) {
-      return ImmutableList.of();
+      // If there's no @CopyAnnotations, we will still copy a @Nullable annotation, if (1) it is not
+      // a TYPE_USE annotation (those appear as part of the type in the generated code) and (2) it
+      // applies to fields. All known non-TYPE_USE @Nullable annotations do apply to fields, but we
+      // check just in case.
+      return method.getAnnotationMirrors().stream()
+          .filter(
+              a -> {
+                TypeElement annotationType = asType(a.getAnnotationType().asElement());
+                return isNullable(a)
+                    && !returnTypeAnnotations.contains(annotationType.getQualifiedName().toString())
+                    && annotationAppliesToFields(annotationType);
+              })
+          .collect(toImmutableList());
     }
     ImmutableSet<String> excludedAnnotations =
         ImmutableSet.<String>builder()
             .addAll(getExcludedAnnotationClassNames(method))
             .add(Override.class.getCanonicalName())
             .build();
 
-    // We need to exclude type annotations from the ones being output on the method, since
-    // they will be output as part of the field's type.
-    Set<String> returnTypeAnnotations =
-        getReturnTypeAnnotations(method, this::annotationAppliesToFields);
     Set<String> nonFieldAnnotations =
         method.getAnnotationMirrors().stream()
             .map(a -> a.getAnnotationType().asElement())

value/src/test/java/com/google/auto/value/processor/AutoValueCompilationTest.java

@@ -1163,6 +1163,7 @@ public void correctBuilder() {
             "final class AutoValue_Baz<T extends Number> extends Baz<T> {",
             "  private final int anInt;",
             "  private final byte[] aByteArray;",
+            "  @Nullable",
             "  private final int[] aNullableIntArray;",
             "  private final List<T> aList;",
             "  private final ImmutableMap<T, String> anImmutableMap;",