fix(api): Don't throw an exception if a PointersSupplier has no parent

Author: kezz

api/src/main/java/net/kyori/adventure/pointer/PointersSupplierImpl.java

@@ -33,7 +33,7 @@
 import org.jetbrains.annotations.Nullable;
 
 final class PointersSupplierImpl<T> implements PointersSupplier<T> {
-  private final PointersSupplier<? super T> parent;
+  private final @Nullable PointersSupplier<? super T> parent;
   private final Map<Pointer<?>, Function<T, ?>> resolvers;
 
   PointersSupplierImpl(final @NotNull BuilderImpl<T> builder) {
@@ -87,7 +87,10 @@ static final class ForwardingPointers<U> implements Pointers {
 
       // Fallback to the parent.
       if (resolver == null) {
-        resolver = this.supplier.parent.resolver(pointer);
+        final PointersSupplier<? super U> parent = this.supplier.parent;
+        if (parent != null) {
+          resolver = this.supplier.parent.resolver(pointer);
+        }
       }
 
       // Finally, wrap in an optional.
@@ -117,7 +120,7 @@ public <T> boolean supports(final @NotNull Pointer<T> pointer) {
   }
 
   static final class BuilderImpl<T> implements Builder<T> {
-    private PointersSupplier<? super T> parent = null;
+    private @Nullable PointersSupplier<? super T> parent = null;
     private final Map<Pointer<?>, Function<T, ?>> resolvers;
 
     BuilderImpl() {

api/src/test/java/net/kyori/adventure/pointer/PointersTest.java

@@ -90,4 +90,25 @@ public void ofPointersSuppliers() {
     assertEquals("1", rebuilt.get(p0).get());
     assertEquals("1", rebuilt.get(p1).get());
   }
+
+  @Test
+  public void ofPointersSuppliersWithNoParent() {
+    final Pointer<String> p0 = Pointer.pointer(String.class, Key.key("adventure:test1"));
+    final Pointer<String> p1 = Pointer.pointer(String.class, Key.key("adventure:test2"));
+
+    final PointersSupplier<Integer> supplier = PointersSupplier.<Integer>builder()
+      .resolving(p1, (object) -> "1")
+      .build();
+
+    assertFalse(supplier.supports(p0));
+    assertTrue(supplier.supports(p1));
+
+    final Pointers pointer = supplier.view(10);
+    assertFalse(pointer.get(p0).isPresent());
+    assertEquals("1", pointer.get(p1).get());
+
+    final Pointers rebuilt = pointer.toBuilder().withStatic(p0, "1").build();
+    assertEquals("1", rebuilt.get(p0).get());
+    assertEquals("1", rebuilt.get(p1).get());
+  }
 }