[automation] Allow returning null from supplier function in ValueCache

In some cases, it is useful to be able to return null from the supplier function using null as an "unspecified" value.

Signed-off-by: Florian Hotze <[email protected]>

bundles/org.openhab.core.automation.module.script.rulesupport/src/main/java/org/openhab/core/automation/module/script/rulesupport/internal/CacheScriptExtension.java

@@ -173,7 +173,7 @@ public ValueCacheImpl(String scriptIdentifier) {
 
         @Override
         public Object get(String key, Supplier<Object> supplier) {
-            return Objects.requireNonNull(cache.computeIfAbsent(key, k -> supplier.get()));
+            return cache.computeIfAbsent(key, k -> supplier.get());
         }
 
         private Collection<Object> values() {
@@ -235,7 +235,7 @@ public Object get(String key, Supplier<Object> supplier) {
             cacheLock.lock();
             try {
                 rememberAccessToKey(key);
-                Object value = Objects.requireNonNull(sharedCache.computeIfAbsent(key, k -> supplier.get()));
+                Object value = sharedCache.computeIfAbsent(key, k -> supplier.get());
 
                 logger.trace("GET with supplier to cache from '{}': '{}' -> '{}'", scriptIdentifier, key, value);
                 return value;

bundles/org.openhab.core.automation.module.script.rulesupport/src/main/java/org/openhab/core/automation/module/script/rulesupport/shared/ValueCache.java

@@ -58,8 +58,9 @@ public interface ValueCache {
      * Get a value from the cache or create a new key-value-pair from the given supplier
      *
      * @param key the key of the requested value
-     * @param supplier a supplier that returns a non-null value to be used if the key was not present
+     * @param supplier a supplier that returns a value to be used if the key was not present
      * @return the value associated with the key
      */
+    @Nullable
     Object get(String key, Supplier<Object> supplier);
 }