Issue jakartaee#829 empty restriction

Signed-off-by: Nathan Rauh <[email protected]>

api/src/main/java/jakarta/data/metamodel/restrict/EmptyRestriction.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2025 Contributors to the Eclipse Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package jakarta.data.metamodel.restrict;
+
+import java.util.List;
+
+class EmptyRestriction<T> implements CompositeRestriction<T> {
+    static final EmptyRestriction<?> INSTANCE = new EmptyRestriction<>();
+
+    // prevent instantiation by others
+    private EmptyRestriction() {
+    }
+
+    @Override
+    public boolean isNegated() {
+        return false;
+    }
+
+    @Override
+    public CompositeRestriction<T> negate() {
+        throw new UnsupportedOperationException("Empty restriction cannot be negated.");
+    }
+
+    @Override
+    public List<Restriction<T>> restrictions() {
+        return List.of();
+    }
+
+    @Override
+    public Type type() {
+        return Type.ALL;
+    }
+}

api/src/main/java/jakarta/data/metamodel/restrict/Restrict.java

@@ -132,6 +132,11 @@ public static <T> TextRestriction<T> like(String pattern,
         return new TextRestrictionRecord<>(attribute, Operator.LIKE, ESCAPED, p);
     }
 
+    @SuppressWarnings("unchecked")
+    public static final <T> Restriction<T> none() {
+        return (Restriction<T>) EmptyRestriction.INSTANCE;
+    }
+
     // convenience method for those who would prefer to avoid .negate()
     public static <T> Restriction<T> not(Restriction<T> restriction) {
         Objects.requireNonNull(restriction, "Restriction must not be null");