Fix NPE when evaluating objects that can lead to cycle/infinite recur…

…sion (#1868)

src/main/java/org/assertj/core/api/recursive/comparison/DualValue.java

@@ -222,7 +222,10 @@ private static boolean isPotentialCyclingValue(Object object) {
     if (object == null) return false;
     // java.lang are base types that can't cycle to themselves of other types
     // we could check more type, but that's a good start
-    return !object.getClass().getCanonicalName().startsWith("java.lang");
+    String canonicalName = object.getClass().getCanonicalName();
+    // canonicalName is null for anonymous and local classes, return true as they can cycle back to other objects.
+    if (canonicalName == null) return true;
+    return !canonicalName.startsWith("java.lang");
   }
 
 }

src/test/java/org/assertj/core/api/recursive/comparison/ColorWithCode.java

@@ -0,0 +1,48 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ *
+ * Copyright 2012-2020 the original author or authors.
+ */
+package org.assertj.core.api.recursive.comparison;
+
+import static org.assertj.core.api.recursive.comparison.ColorWithCode.GREEN;
+
+enum ColorWithCode {
+  RED {
+    @Override
+    String code() {
+      return "#FF0000";
+    }
+  },
+  GREEN {
+    @Override
+    String code() {
+      return "#00FF00";
+    }
+  },
+  BLUE {
+    @Override
+    String code() {
+      return "#0000FF";
+    }
+  };
+
+  abstract String code();
+
+}
+
+class Theme {
+  ColorWithCode color = GREEN;
+
+  public Theme(ColorWithCode color) {
+    this.color = color;
+  }
+
+}

src/test/java/org/assertj/core/api/recursive/comparison/DualValue_hasPotentialCyclingValues_Test.java

@@ -13,6 +13,8 @@
 package org.assertj.core.api.recursive.comparison;
 
 import static org.assertj.core.api.BDDAssertions.then;
+import static org.assertj.core.api.recursive.comparison.Color.GREEN;
+import static org.assertj.core.api.recursive.comparison.ColorWithCode.RED;
 import static org.assertj.core.util.Lists.list;
 
 import java.util.List;
@@ -49,6 +51,13 @@ static Stream<Arguments> values() {
     person2.otherFriends.add(person2);
     person2.otherFriends.add(person1);
 
+    class LocalClass {
+      @Override
+      public String toString() {
+        return "LocalClass";
+      }
+    }
+
     return Stream.of(Arguments.of(null, person2, false),
                      Arguments.of(person1, null, false),
                      Arguments.of(person1, "abc", false),
@@ -64,6 +73,20 @@ static Stream<Arguments> values() {
                      Arguments.of(person1, person2, true),
                      Arguments.of(list(person1), list(person1), true),
                      Arguments.of(list(person1), list(person2), true),
+                     Arguments.of(new LocalClass(), new LocalClass(), true),
+                     Arguments.of(new Light(GREEN), new Light(GREEN), true),
+                     Arguments.of(new Theme(RED), new Theme(RED), true), // for #1866
+                     Arguments.of(new DualValue_hasPotentialCyclingValues_Test().new Inner(),
+                                  new DualValue_hasPotentialCyclingValues_Test().new Inner(), true),
                      Arguments.of(list(person1, person2), list(person2, person1), true));
   }
+
+  class Inner {
+    @Override
+    public String toString() {
+      return "Inner Class";
+    }
+
+  }
+
 }

src/test/java/org/assertj/core/api/recursive/comparison/RecursiveComparisonAssert_isEqualTo_Test.java

@@ -17,6 +17,7 @@
 import static org.assertj.core.api.BDDAssertions.then;
 import static org.assertj.core.api.recursive.comparison.Color.BLUE;
 import static org.assertj.core.api.recursive.comparison.Color.GREEN;
+import static org.assertj.core.api.recursive.comparison.ColorWithCode.RED;
 import static org.assertj.core.error.ShouldBeEqual.shouldBeEqual;
 import static org.assertj.core.error.ShouldNotBeNull.shouldNotBeNull;
 import static org.assertj.core.test.AlwaysEqualComparator.ALWAY_EQUALS_STRING;
@@ -171,6 +172,7 @@ private static Stream<Arguments> recursivelyEqualObjects() {
     return Stream.of(arguments(person1, person2, "same data, same type"),
                      arguments(person2, person1, "same data, same type reversed"),
                      arguments(person3, person4, "same data, different type"),
+                     arguments(new Theme(RED), new Theme(RED), "same data with enum overriding methods - covers #1866"),
                      arguments(person4, person3, "same data, different type"));
   }
 

src/test/java/org/assertj/core/internal/objects/data/FriendlyPerson.java

@@ -22,11 +22,11 @@ public class FriendlyPerson extends Person {
   public Set<FriendlyPerson> otherFriends = new HashSet<>();
 
   public FriendlyPerson() {
-      super();
+    super();
   }
 
   public FriendlyPerson(String name) {
-      super(name);
+    super(name);
   }
 
   public static FriendlyPerson friend(String name) {