From c76e6f502843d6233b487466c398c0fe2c4d4376 Mon Sep 17 00:00:00 2001
From: Lazaro Clapp <lazaro@uber.com>
Date: Fri, 29 Mar 2019 13:26:05 -0400
Subject: [PATCH] Warn about unsupported @Nullable var args case.

---
 .../java/com/uber/nullaway/ErrorMessage.java  |  1 +
 .../main/java/com/uber/nullaway/NullAway.java | 21 ++++++++++++++++---
 .../java/com/uber/nullaway/NullAwayTest.java  | 21 +++++++++++++++++++
 3 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/nullaway/src/main/java/com/uber/nullaway/ErrorMessage.java b/nullaway/src/main/java/com/uber/nullaway/ErrorMessage.java
index 15d1910cb6..6b12e8c680 100644
--- a/nullaway/src/main/java/com/uber/nullaway/ErrorMessage.java
+++ b/nullaway/src/main/java/com/uber/nullaway/ErrorMessage.java
@@ -48,6 +48,7 @@ public enum MessageTypes {
     FIELD_NO_INIT,
     UNBOX_NULLABLE,
     NONNULL_FIELD_READ_BEFORE_INIT,
+    NULLABLE_VARARGS_UNSUPPORTED,
     ANNOTATION_VALUE_INVALID,
     CAST_TO_NONNULL_ARG_NONNULL,
     GET_ON_EMPTY_OPTIONAL;
diff --git a/nullaway/src/main/java/com/uber/nullaway/NullAway.java b/nullaway/src/main/java/com/uber/nullaway/NullAway.java
index 3b5e848013..154d69fef3 100644
--- a/nullaway/src/main/java/com/uber/nullaway/NullAway.java
+++ b/nullaway/src/main/java/com/uber/nullaway/NullAway.java
@@ -487,10 +487,25 @@ public Description matchMethod(MethodTree tree, VisitorState state) {
     if (isOverriding || !exhaustiveOverride) {
       Symbol.MethodSymbol closestOverriddenMethod =
           getClosestOverriddenMethod(methodSymbol, state.getTypes());
-      if (closestOverriddenMethod == null) {
-        return Description.NO_MATCH;
+      if (closestOverriddenMethod != null) {
+        return checkOverriding(closestOverriddenMethod, methodSymbol, null, state);
+      }
+    }
+    // Check that var args (if any) is @Nullable, as NullAway doesn't currently support this case
+    if (methodSymbol.isVarArgs()) {
+      VarSymbol varArgsSymbol =
+          methodSymbol.getParameters().get(methodSymbol.getParameters().size() - 1);
+      if (Nullness.hasNullableAnnotation(varArgsSymbol)) {
+        String message =
+            "NullAway doesn't currently support @Nullable VarArgs. "
+                + "Consider removing the @Nullable annotation from "
+                + varArgsSymbol.toString()
+                + " in "
+                + methodSymbol.toString()
+                + " (this issue can cause other errors below, wherever the var args array is dereferenced)";
+        return createErrorDescription(
+            MessageTypes.NULLABLE_VARARGS_UNSUPPORTED, tree, message, state.getPath());
       }
-      return checkOverriding(closestOverriddenMethod, methodSymbol, null, state);
     }
     return Description.NO_MATCH;
   }
diff --git a/nullaway/src/test/java/com/uber/nullaway/NullAwayTest.java b/nullaway/src/test/java/com/uber/nullaway/NullAwayTest.java
index a6151acdc5..8e1bb802e4 100644
--- a/nullaway/src/test/java/com/uber/nullaway/NullAwayTest.java
+++ b/nullaway/src/test/java/com/uber/nullaway/NullAwayTest.java
@@ -1707,6 +1707,27 @@ public void testNonNullVarargs() {
         .doTest();
   }
 
+  @Test
+  public void testNullableVarargs() {
+    compilationHelper
+        .addSourceLines(
+            "Utilities.java",
+            "package com.uber;",
+            "import javax.annotation.Nullable;",
+            "public class Utilities {",
+            " // BUG: Diagnostic contains: NullAway doesn't currently support @Nullable VarArgs",
+            " public static String takesNullableVarargs(Object o, @Nullable Object... others) {",
+            "  String s = o.toString() + \" \";",
+            "  // BUG: Diagnostic contains: enhanced-for expression others is @Nullable",
+            "  for (Object other : others) {",
+            "    s += (other == null) ? \"(null) \" : other.toString() + \" \";",
+            "  }",
+            "  return s;",
+            " }",
+            "}")
+        .doTest();
+  }
+
   @Test
   public void testNonNullVarargsFromHandler() {
     String generatedAnnot =