Fix to handling of case null (#1235)

msridhar · web-flow · commit ee85996d99fe · 2025-08-04T14:30:35.000Z
diff --git a/jdk-recent-unit-tests/src/test/java/com/uber/nullaway/jdk17/SwitchTests.java b/jdk-recent-unit-tests/src/test/java/com/uber/nullaway/jdk17/SwitchTests.java
@@ -268,6 +268,29 @@ public void switchStatementCaseNull() {
         .doTest();
   }
 
+  @Test
+  public void caseNullTypeRefinement() {
+    defaultCompilationHelper
+        .addSourceLines(
+            "TestCase.java",
+            "import java.io.IOException;",
+            "import org.jspecify.annotations.NullMarked;",
+            "@NullMarked",
+            "public class TestCase {",
+            "    boolean hasRelevantMessage(IOException ioException)",
+            "    {",
+            "        String message = ioException.getMessage();",
+            "        return switch (message)",
+            "        {",
+            "            case null -> false;",
+            "            case \"Operation timed out\", \"Connection reset by peer\", \"Premature EOF\", \"Error writing to server\" -> true;",
+            "            default -> message.contains(\"GOAWAY received\");",
+            "        };",
+            "    }",
+            "}")
+        .doTest();
+  }
+
   @Test
   public void issue1168() {
     defaultCompilationHelper
diff --git a/nullaway/src/main/java/com/uber/nullaway/dataflow/AccessPathNullnessPropagation.java b/nullaway/src/main/java/com/uber/nullaway/dataflow/AccessPathNullnessPropagation.java
@@ -411,21 +411,23 @@ public TransferResult<Nullness, NullnessStore> visitGreaterThanOrEqual(
   public TransferResult<Nullness, NullnessStore> visitEqualTo(
       EqualToNode equalToNode, TransferInput<Nullness, NullnessStore> input) {
     return handleEqualityComparison(
-        input, equalToNode.getLeftOperand(), equalToNode.getRightOperand(), true);
+        input, equalToNode.getLeftOperand(), null, equalToNode.getRightOperand(), true);
   }
 
   @Override
   public TransferResult<Nullness, NullnessStore> visitNotEqual(
       NotEqualNode notEqualNode, TransferInput<Nullness, NullnessStore> input) {
     return handleEqualityComparison(
-        input, notEqualNode.getLeftOperand(), notEqualNode.getRightOperand(), false);
+        input, notEqualNode.getLeftOperand(), null, notEqualNode.getRightOperand(), false);
   }
 
   /**
    * Handle nullability refinements from an equality comparison.
    *
    * @param input transfer input for the operation
    * @param leftOperand left operand of the comparison
+   * @param leftOperandNullness nullness of left operand if it is not a sub node of {@code
+   *     input.getNode()}, {@code null} otherwise
    * @param rightOperand right operand of the comparison
    * @param equalTo if {@code true}, the comparison is an equality comparison, otherwise it is a
    *     dis-equality ({@code !=}) comparison
@@ -434,12 +436,14 @@ public TransferResult<Nullness, NullnessStore> visitNotEqual(
   private TransferResult<Nullness, NullnessStore> handleEqualityComparison(
       TransferInput<Nullness, NullnessStore> input,
       Node leftOperand,
+      @Nullable Nullness leftOperandNullness,
       Node rightOperand,
       boolean equalTo) {
     ReadableUpdates thenUpdates = new ReadableUpdates();
     ReadableUpdates elseUpdates = new ReadableUpdates();
     SubNodeValues inputs = values(input);
-    Nullness leftVal = inputs.valueOfSubNode(leftOperand);
+    Nullness leftVal =
+        leftOperandNullness != null ? leftOperandNullness : inputs.valueOfSubNode(leftOperand);
     Nullness rightVal = inputs.valueOfSubNode(rightOperand);
     Nullness equalBranchValue = leftVal.greatestLowerBound(rightVal);
     Updates equalBranchUpdates = equalTo ? thenUpdates : elseUpdates;
@@ -965,7 +969,14 @@ public TransferResult<Nullness, NullnessStore> visitCase(
       // between the switch expression and the case operand.
       Node switchOperand = caseNode.getSwitchOperand().getExpression();
       Node caseOperand = caseOperands.get(0);
-      return handleEqualityComparison(input, switchOperand, caseOperand, true);
+      AccessPath switchOperandAccessPath =
+          AccessPath.getAccessPathForNode(switchOperand, state, apContext);
+      Nullness switchOperandNullness =
+          switchOperandAccessPath == null
+              ? null
+              : input.getRegularStore().getNullnessOfAccessPath(switchOperandAccessPath);
+      return handleEqualityComparison(
+          input, switchOperand, switchOperandNullness, caseOperand, true);
     }
   }
 
