Avoid suggesting castToNonNull fixes in certain cases

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

@@ -203,6 +203,9 @@ private Description.Builder addSuggestedSuppression(
         if (config.getCastToNonNullMethod() != null && canBeCastToNonNull(suggestTree)) {
           builder = addCastToNonNullFix(suggestTree, builder);
         } else {
+          // When there is a castToNonNull method, suggestTree is set to the expression to be
+          // casted, which is not suppressible.  For simplicity, we just always recompute the
+          // suppressible node here.
           Tree suppressibleNode = suppressibleNode(state.getPath());
           if (suppressibleNode != null) {
             builder = addSuppressWarningsFix(suppressibleNode, builder, suppressionName);
@@ -392,8 +395,8 @@ private Description.Builder removeCastToNonNullFix(
   }
 
   /**
-   * Reports initialization errors where a constructor fails to guarantee non-fields are initialized
-   * along all paths at exit points.
+   * Reports initialization errors where a constructor fails to guarantee non-null fields are
+   * initialized along all paths at exit points.
    *
    * @param methodSymbol Constructor symbol.
    * @param message Error message.

nullaway/src/test/java/com/uber/nullaway/NullAwayAutoSuggestTest.java

@@ -24,6 +24,7 @@
 
 import com.google.errorprone.BugCheckerRefactoringTestHelper;
 import com.google.errorprone.ErrorProneFlags;
+import com.sun.source.tree.Tree;
 import com.uber.nullaway.testlibrarymodels.TestLibraryModels;
 import java.io.IOException;
 import org.junit.Before;
@@ -111,6 +112,10 @@ public void suggestCastToNonNull() throws IOException {
         .doTest();
   }
 
+  /**
+   * Test for cases where we heuristically decide not to wrap an expression in castToNonNull; see
+   * {@link ErrorBuilder#canBeCastToNonNull(Tree)}
+   */
   @Test
   public void suppressInsteadOfCastToNonNull() throws IOException {
     makeTestHelper()
@@ -119,24 +124,41 @@ public void suppressInsteadOfCastToNonNull() throws IOException {
             "package com.uber;",
             "import javax.annotation.Nullable;",
             "class Test {",
+            "  Object f = new Object();",
             "  Object test1(@Nullable Object o) {",
             "    return o;",
             "  }",
             "  Object test2() {",
             "    return null;",
             "  }",
+            "  void test3() {",
+            "    f = null;",
+            "  }",
+            "  @Nullable Object m() { return null; }",
+            "  Object shouldAddCast() {",
+            "    return m();",
+            "  }",
             "}")
         .addOutputLines(
             "out/Test.java",
             "package com.uber;",
+            "import static com.uber.nullaway.testdata.Util.castToNonNull;",
             "import javax.annotation.Nullable;",
             "class Test {",
+            "  Object f = new Object();",
             "  @SuppressWarnings(\"NullAway\") Object test1(@Nullable Object o) {",
             "    return o;",
             "  }",
             "  @SuppressWarnings(\"NullAway\") Object test2() {",
             "    return null;",
             "  }",
+            "  @SuppressWarnings(\"NullAway\") void test3() {",
+            "    f = null;",
+            "  }",
+            "  @Nullable Object m() { return null; }",
+            "  Object shouldAddCast() {",
+            "    return castToNonNull(m());",
+            "  }",
             "}")
         .doTest();
   }
@@ -234,4 +256,68 @@ public void suggestSuppressionOnMethodRef() throws IOException {
             "}")
         .doTest();
   }
+
+  @Test
+  public void suggestInitSuppressionOnConstructor() throws IOException {
+    makeTestHelper()
+        .addInputLines(
+            "Test.java",
+            "package com.uber;",
+            "import javax.annotation.Nullable;",
+            "class Test {",
+            "  Object f;",
+            "  Object g;",
+            "  Test() {}",
+            "}")
+        .addOutputLines(
+            "out/Test.java",
+            "package com.uber;",
+            "import javax.annotation.Nullable;",
+            "class Test {",
+            "  Object f;",
+            "  Object g;",
+            "  @SuppressWarnings(\"NullAway.Init\") Test() {}",
+            "}")
+        .doTest();
+  }
+
+  @Test
+  public void suggestInitSuppressionOnField() throws IOException {
+    makeTestHelper()
+        .addInputLines(
+            "Test.java",
+            "package com.uber;",
+            "import javax.annotation.Nullable;",
+            "class Test {",
+            "  Object f;",
+            "}")
+        .addOutputLines(
+            "out/Test.java",
+            "package com.uber;",
+            "import javax.annotation.Nullable;",
+            "class Test {",
+            "  @SuppressWarnings(\"NullAway.Init\") Object f;",
+            "}")
+        .doTest();
+  }
+
+  @Test
+  public void updateExtantSuppressWarnings() throws IOException {
+    makeTestHelper()
+        .addInputLines(
+            "Test.java",
+            "package com.uber;",
+            "import javax.annotation.Nullable;",
+            "class Test {",
+            "  @SuppressWarnings(\"unused\") Object f;",
+            "}")
+        .addOutputLines(
+            "out/Test.java",
+            "package com.uber;",
+            "import javax.annotation.Nullable;",
+            "class Test {",
+            "  @SuppressWarnings({\"unused\",\"NullAway.Init\"}) Object f;",
+            "}")
+        .doTest();
+  }
 }