Check for nulls

Author: leonard84

spock-core/src/main/java/org/spockframework/runtime/NamespacedExtensionStore.java

@@ -4,6 +4,7 @@
 import org.junit.platform.engine.support.store.NamespacedHierarchicalStoreException;
 import org.spockframework.runtime.extension.IStore;
 
+import java.util.Objects;
 import java.util.function.Function;
 import java.util.function.Supplier;
 
@@ -12,10 +13,10 @@ public class NamespacedExtensionStore implements IStore {
   private final Supplier<NamespacedExtensionStore> parentProvider;
   private final IStore.Namespace namespace;
 
-  public NamespacedExtensionStore(NamespacedHierarchicalStore<Namespace> delegate, Supplier<NamespacedExtensionStore> parentProvider, Namespace namespace) {
-    this.delegate = delegate;
-    this.parentProvider = parentProvider;
-    this.namespace = namespace;
+  NamespacedExtensionStore(NamespacedHierarchicalStore<Namespace> delegate, Supplier<NamespacedExtensionStore> parentProvider, Namespace namespace) {
+    this.delegate = Objects.requireNonNull(delegate);
+    this.parentProvider =  Objects.requireNonNull(parentProvider);
+    this.namespace =  Objects.requireNonNull(namespace);
   }
 
   @SuppressWarnings("unchecked")

spock-core/src/main/java/org/spockframework/runtime/SpockExecution.java

@@ -3,11 +3,13 @@
 import org.spockframework.runtime.extension.ISpockExecution;
 import org.spockframework.runtime.extension.IStore;
 
+import java.util.Objects;
+
 public class SpockExecution implements ISpockExecution {
   private final StoreProvider storeProvider;
 
   public SpockExecution(StoreProvider storeProvider) {
-    this.storeProvider = storeProvider;
+    this.storeProvider = Objects.requireNonNull(storeProvider);
   }
 
   @Override

spock-core/src/main/java/org/spockframework/runtime/StoreProvider.java

@@ -4,20 +4,21 @@
 import org.spockframework.runtime.extension.IStore;
 import org.spockframework.util.Nullable;
 
+import java.util.Objects;
+
 public class StoreProvider implements AutoCloseable {
   private static final NamespacedHierarchicalStore.CloseAction<IStore.Namespace> CLOSE_ACTION = (IStore.Namespace namespace, Object key, Object value) -> {
     if (value instanceof AutoCloseable) {
       ((AutoCloseable) value).close();
     }
   };
 
-  @Nullable
   private final NamespacedHierarchicalStore<IStore.Namespace> backend;
   @Nullable
   private final StoreProvider parent;
 
   private StoreProvider(NamespacedHierarchicalStore<IStore.Namespace> backend, StoreProvider parent) {
-    this.backend = backend;
+    this.backend = Objects.requireNonNull(backend);
     this.parent = parent;
   }