SONARJAVA-4390 NPE in ECJ should be catched by JType.isSubtype(...)

java-frontend/src/main/java/org/sonar/java/model/JType.java

@@ -20,6 +20,8 @@
 package org.sonar.java.model;
 
 import org.eclipse.jdt.core.dom.ITypeBinding;
+import org.sonar.api.utils.log.Logger;
+import org.sonar.api.utils.log.Loggers;
 import org.sonar.plugins.java.api.semantic.Symbol;
 import org.sonar.plugins.java.api.semantic.Type;
 
@@ -31,6 +33,8 @@
 
 final class JType implements Type, Type.ArrayType {
 
+  private static final Logger LOG = Loggers.get(JType.class);
+
   final JSema sema;
   final ITypeBinding typeBinding;
 
@@ -70,7 +74,13 @@ private static boolean isSubtype(ITypeBinding left, ITypeBinding right) {
     if (left.isNullType()) {
       return !right.isPrimitive();
     }
-    return left.isSubTypeCompatible(right);
+    try {
+      return left.isSubTypeCompatible(right);
+    } catch (NullPointerException ex) {
+      // In rare circumstances, ECJ may produce a NPE while calling isSubTypeCompatible(), see SONARJAVA-4390
+      LOG.debug("NullPointerException while resolving isSubTypeCompatible()", ex);
+      return false;
+    }
   }
 
   @Override

java-frontend/src/test/java/org/sonar/java/model/JTypeTest.java

@@ -19,14 +19,19 @@
  */
 package org.sonar.java.model;
 
+import java.util.Objects;
+import java.util.stream.Stream;
 import org.eclipse.jdt.core.dom.AST;
 import org.eclipse.jdt.core.dom.ASTParser;
 import org.eclipse.jdt.core.dom.ITypeBinding;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
+import org.sonar.api.utils.log.LogTesterJUnit5;
+import org.sonar.api.utils.log.LoggerLevel;
 import org.sonar.java.model.JavaTree.CompilationUnitTreeImpl;
 import org.sonar.java.model.declaration.ClassTreeImpl;
 import org.sonar.java.model.declaration.MethodTreeImpl;
@@ -35,15 +40,18 @@
 import org.sonar.java.model.statement.ReturnStatementTreeImpl;
 import org.sonar.plugins.java.api.semantic.Type;
 
-import java.util.Objects;
-import java.util.stream.Stream;
-
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertAll;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.when;
 import static org.sonar.java.model.assertions.TypeAssert.assertThat;
 
 class JTypeTest {
 
+  @RegisterExtension
+  public LogTesterJUnit5 logTester = new LogTesterJUnit5();
+
   @Test
   void isArray() {
     assertThat(type("int[]").isArray())
@@ -258,6 +266,22 @@ void null_type() {
       .isNotSubtypeOf(primitiveType);
   }
 
+  @Test
+  void is_subtype_of_should_not_throw_NPE() {
+    JType objectType = type("java.lang.Object");
+    ITypeBinding brokenStringBinding = spy(Objects.requireNonNull(sema.resolveType("java.lang.String")));
+    // simulate the NullPointerException described in SONARJAVA-4390
+    when(brokenStringBinding.isSubTypeCompatible(any()))
+      .thenThrow(new NullPointerException("test NPE"));
+
+    JType stringType = new JType(sema, brokenStringBinding);
+    // should catch the NullPointerException
+    assertThat(stringType.isSubtypeOf(objectType)).isFalse();
+
+    assertThat(logTester.logs(LoggerLevel.DEBUG))
+      .containsExactly("NullPointerException while resolving isSubTypeCompatible()");
+  }
+
   @Test
   void wildcard() {
     JavaTree.CompilationUnitTreeImpl cu = test("class C<T1, T2, T3> { C<? extends String, ? extends String, ? super String> f; }");