fix null handling in equals(), add tests

Author: Vladimir Kotal

opengrok-indexer/src/main/java/org/opengrok/indexer/history/HistoryEntry.java

@@ -18,7 +18,7 @@
  */
 
 /*
- * Copyright (c) 2006, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2021, Oracle and/or its affiliates. All rights reserved.
  * Portions Copyright (c) 2019, Chris Fraire <[email protected]>.
  */
 package org.opengrok.indexer.history;
@@ -215,6 +215,14 @@ public void stripTags() {
         tags = null;
     }
 
+    private boolean checkEquals(Object o1, Object o2) {
+        if (o1 != null && o2 != null) {
+            return o1.equals(o2);
+        }
+
+        return (o1 == null && o2 == null);
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) {
@@ -224,14 +232,13 @@ public boolean equals(Object o) {
             return false;
         }
         HistoryEntry that = (HistoryEntry) o;
-        // TODO: more robust w.r.t. null
-        return this.getAuthor().equals(that.getAuthor()) &&
-                this.getRevision().equals(that.getRevision()) &&
-                this.getDate().equals(that.getDate()) &&
-                this.getMessage().equals(that.getMessage()) &&
-                this.getFiles().equals(that.getFiles()) &&
-                (this.getTags() != null && that.getTags() != null ?
-                        this.getTags().equals(that.getTags()) : this.getTags() == null && that.getTags() == null);
+
+        return checkEquals(this.getAuthor(), that.getAuthor()) &&
+                checkEquals(this.getRevision(), that.getRevision()) &&
+                checkEquals(this.getDate(), that.getDate()) &&
+                checkEquals(this.getMessage(), that.getMessage()) &&
+                checkEquals(this.getFiles(), that.getFiles()) &&
+                checkEquals(this.getTags(), that.getTags());
     }
 
     @Override

opengrok-indexer/src/test/java/org/opengrok/indexer/history/HistoryEntryTest.java

@@ -32,6 +32,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertNotSame;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
@@ -248,10 +249,24 @@ public void strip() {
     }
 
     @Test
-    public void testEquals() {
-        // TODO: add tests with nulls
+    public void testEqualsCopyConstructor() {
         HistoryEntry e = new HistoryEntry(instance);
         assertNotSame(e, instance);
         assertEquals(e, instance);
     }
+
+    @Test
+    public void testEqualsEmpty() {
+        HistoryEntry e = new HistoryEntry();
+        assertNotSame(e, instance);
+        assertNotEquals(e, instance);
+    }
+
+    @Test
+    public void testEquals() {
+        HistoryEntry e = new HistoryEntry(historyRevision, historyDate,
+                historyAuthor, null, historyMessage, true);
+        assertNotSame(e, instance);
+        assertEquals(e, instance);
+    }
 }