B!! fixed type and nullpointer bugs in combine

Co-Authored-By: Llewellyn Falco <[email protected]>

Author: lexler

approvaltests-util-tests/src/test/java/com/spun/util/ArrayUtilsTest.java

@@ -47,6 +47,54 @@ public void testCombineArrays()
     String empty = null;
     assertEquals("[null]", Arrays.toString(ArrayUtils.combine(empty)));
   }
+  public interface I
+  {
+  }
+  public static class BrotherA implements I
+  {
+    @Override
+    public String toString()
+    {
+      return "BrotherA";
+    }
+  }
+  public static class BrotherB implements I
+  {
+    @Override
+    public String toString()
+    {
+      return "BrotherB";
+    }
+  }
+  public static class ChildOfA extends BrotherA
+  {
+    @Override
+    public String toString()
+    {
+      return "ChildOfA";
+    }
+  }
+  @Test
+  void testCoAndContraVariance()
+  {
+    Integer nullObject = null;
+    Object[][] result = new Object[][]{ArrayUtils.combine(new BrotherA(), new ChildOfA()),
+                                       ArrayUtils.combine(new BrotherA(), new BrotherB()),
+                                       ArrayUtils.combine(new BrotherB(), new BrotherA()),
+                                       ArrayUtils.combine(new BrotherB(), new BrotherB()),
+                                       ArrayUtils.combine(new ChildOfA(), new BrotherA()),
+                                       ArrayUtils.combine(null, new BrotherA(), new ChildOfA()),
+                                       ArrayUtils.combine(null, new BrotherA(), new BrotherA()),
+                                       ArrayUtils.combine(null, new BrotherA(), new BrotherA(), new BrotherA()),
+                                       ArrayUtils.combine(new BrotherA(), null, null),
+                                       ArrayUtils.combine(new BrotherA(), new BrotherA[]{null}),
+                                       ArrayUtils.combine(new BrotherA()),
+                                       ArrayUtils.combine(null),
+                                       ArrayUtils.combine(new BrotherA(), null),
+                                       ArrayUtils.combine(nullObject, null),};
+    Approvals.verifyAll("", result,
+        a -> String.format("%s = %s", a.getClass().getSimpleName(), Arrays.toString(a)));
+  }
   @Test
   void testToArray()
   {

approvaltests-util-tests/src/test/java/com/spun/util/ArrayUtilsTest.testCoAndContraVariance.approved.txt

@@ -0,0 +1,14 @@
+BrotherA[] = [BrotherA, ChildOfA]
+I[] = [BrotherA, BrotherB]
+I[] = [BrotherB, BrotherA]
+BrotherB[] = [BrotherB, BrotherB]
+BrotherA[] = [ChildOfA, BrotherA]
+BrotherA[] = [null, BrotherA, ChildOfA]
+BrotherA[] = [null, BrotherA, BrotherA]
+BrotherA[] = [null, BrotherA, BrotherA, BrotherA]
+BrotherA[] = [BrotherA, null, null]
+BrotherA[] = [BrotherA, null]
+BrotherA[] = [BrotherA]
+Object[] = [null]
+BrotherA[] = [BrotherA, null]
+Object[] = [null, null]

approvaltests-util/src/main/java/com/spun/util/ArrayUtils.java

@@ -209,20 +209,27 @@ else if (isEmpty(b))
     }
     else
     {
-      T[] newArray = null;
-      newArray = (T[]) Array.newInstance(a.getClass().getComponentType(), a.length + b.length);
+      T[] newArray = (T[]) Array.newInstance(a.getClass().getComponentType(), a.length + b.length);
       System.arraycopy(a, 0, newArray, 0, a.length);
       System.arraycopy(b, 0, newArray, a.length, b.length);
       return newArray;
     }
   }
   public static <T> T[] combine(T a, T... b)
   {
-    final Class<?> type = a != null ? a.getClass() : b.getClass().getComponentType();
+    if (b == null)
+    {
+      b = (T[]) Array.newInstance(getClassFor(a), 1);
+    }
+    final Class<?> type = b.getClass().getComponentType();
     final T[] toArray = (T[]) Array.newInstance(type, 1);
     toArray[0] = a;
     return combine(toArray, b);
   }
+  private static <T> Class<?> getClassFor(T object)
+  {
+    return object != null ? object.getClass() : Object.class;
+  }
   public static <T> boolean contains(T[] values, T value)
   {
     for (int i = 0; i < values.length; i++)