Don't report initializer warnings on @NullUnmarked constructors / methods (#997)

Fixes #995

Author: msridhar

nullaway/src/main/java/com/uber/nullaway/ErrorBuilder.java

@@ -22,6 +22,7 @@
 
 package com.uber.nullaway;
 
+import static com.uber.nullaway.ASTHelpersBackports.hasDirectAnnotationWithSimpleName;
 import static com.uber.nullaway.ASTHelpersBackports.isStatic;
 import static com.uber.nullaway.ErrorMessage.MessageTypes.FIELD_NO_INIT;
 import static com.uber.nullaway.ErrorMessage.MessageTypes.GET_ON_EMPTY_OPTIONAL;
@@ -415,7 +416,9 @@ void reportInitializerError(
     // Check needed here, despite check in hasPathSuppression because initialization
     // checking happens at the class-level (meaning state.getPath() might not include the
     // method itself).
-    if (symbolHasSuppressWarningsAnnotation(methodSymbol, INITIALIZATION_CHECK_NAME)) {
+    if (symbolHasSuppressWarningsAnnotation(methodSymbol, INITIALIZATION_CHECK_NAME)
+        || hasDirectAnnotationWithSimpleName(
+            methodSymbol, NullabilityUtil.NULLUNMARKED_SIMPLE_NAME)) {
       return;
     }
     Tree methodTree = getTreesInstance(state).getTree(methodSymbol);

nullaway/src/test/java/com/uber/nullaway/jspecify/NullMarkednessTests.java

@@ -1156,4 +1156,21 @@ public void dotClassSanityTest2() {
             "}")
         .doTest();
   }
+
+  @Test
+  public void nullUnmarkedOnConstructorSuppressesInitializerWarnings() {
+    defaultCompilationHelper
+        .addSourceLines(
+            "Foo.java",
+            "package com.uber;",
+            "import org.jspecify.annotations.NullUnmarked;",
+            "import org.jspecify.annotations.Nullable;",
+            "public class Foo {",
+            "  public Object f;",
+            "  @NullUnmarked",
+            "  // No error, because Foo is unmarked",
+            "  public Foo() { }",
+            "}")
+        .doTest();
+  }
 }