Add a reserved namespaces deny list to restrict trait-codegen from using smithy specific namespaces.

smithy-trait-codegen/src/main/java/software/amazon/smithy/traitcodegen/TraitCodegenSettings.java

@@ -6,8 +6,11 @@
 
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 import java.util.Objects;
+import java.util.Set;
 import software.amazon.smithy.model.node.ObjectNode;
+import software.amazon.smithy.utils.SetUtils;
 import software.amazon.smithy.utils.SmithyUnstableApi;
 
 /**
@@ -29,6 +32,15 @@
  */
 @SmithyUnstableApi
 public final class TraitCodegenSettings {
+    private static final String SMITHY_KEYWORD = "smithy";
+    private static final Set<String> RESERVED_NAMESPACES = SetUtils.of("smithy.api",
+            "smithy.framework",
+            "smithy.mqtt",
+            "smithy.openapi",
+            "smithy.protocols",
+            "smithy.rules",
+            "smithy.test",
+            "smithy.waiters");
 
     private final String packageName;
     private final String smithyNamespace;
@@ -53,6 +65,9 @@ public final class TraitCodegenSettings {
             List<String> excludeTags
     ) {
         this.packageName = Objects.requireNonNull(packageName);
+        if (isReservedNamespace(smithyNamespace)) {
+            throw new IllegalArgumentException("The `smithy` namespace and its sub-namespaces are reserved.");
+        }
         this.smithyNamespace = Objects.requireNonNull(smithyNamespace);
         this.headerLines = Objects.requireNonNull(headerLines);
         this.excludeTags = Objects.requireNonNull(excludeTags);
@@ -110,4 +125,26 @@ public List<String> headerLines() {
     public List<String> excludeTags() {
         return excludeTags;
     }
+
+    /**
+     * Checks if a namespace is reserved. A namespace is considered reserved if it is
+     * "smithy", one of the predefined reserved namespaces or if it starts with one of the reserved namespaces followed by a dot.
+     *
+     * @param namespace the namespace to check
+     * @return true if the namespace is reserved, false otherwise
+     */
+    private static boolean isReservedNamespace(String namespace) {
+        String namespaceLowerCase = namespace.toLowerCase(Locale.ROOT);
+        if (namespaceLowerCase.equals(SMITHY_KEYWORD) || RESERVED_NAMESPACES.contains(namespaceLowerCase)) {
+            return true;
+        }
+
+        for (String reserved : RESERVED_NAMESPACES) {
+            if (namespaceLowerCase.startsWith(reserved + ".")) {
+                return true;
+            }
+        }
+
+        return false;
+    }
 }

smithy-trait-codegen/src/test/java/software/amazon/smithy/traitcodegen/TraitCodegenSettingsTest.java

@@ -0,0 +1,91 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package software.amazon.smithy.traitcodegen;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.util.Collections;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+class TraitCodegenSettingsTest {
+
+    @ParameterizedTest
+    @ValueSource(strings = {
+            "smithy",
+            "smithy.api",
+            "smithy.waiters",
+            "smithy.test",
+            "smithy.api.foo",
+            "smithy.waiters.bar",
+            "smithy.test.baz",
+            "Smithy.api",
+            "sMithy",
+            "smithy.API",
+            "smiThy.Api.Baz"
+    })
+    void constructorRejectsReservedNamespaces(String namespace) {
+        IllegalArgumentException exception = assertThrows(IllegalArgumentException.class,
+                () -> new TraitCodegenSettings("com.example",
+                        namespace,
+                        Collections.emptyList(),
+                        Collections.emptyList()));
+        assertEquals("The `smithy` namespace and its sub-namespaces are reserved.", exception.getMessage());
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {
+            "smithy.foo",
+            "smithy.bar.baz",
+            "example.namespace",
+            "my.custom.namespace",
+            "smithy.custom",
+            "smithyapi",
+            "smithy.apiextension"
+    })
+    void constructorAcceptsValidNamespaces(String namespace) {
+        assertDoesNotThrow(() -> new TraitCodegenSettings(
+                "com.example",
+                namespace,
+                Collections.emptyList(),
+                Collections.emptyList()));
+    }
+
+    @ParameterizedTest
+    @MethodSource("nullParameterCombinations")
+    void constructorRequiresNonNullParameters(String packageName, String namespace) {
+        assertThrows(NullPointerException.class,
+                () -> new TraitCodegenSettings(packageName,
+                        namespace,
+                        Collections.emptyList(),
+                        Collections.emptyList()));
+    }
+
+    static Stream<Arguments> nullParameterCombinations() {
+        return Stream.of(
+                Arguments.of(null, "smithy.foo"),
+                Arguments.of("com.example", null));
+    }
+
+    @Test
+    void gettersReturnCorrectValues() {
+        TraitCodegenSettings settings = new TraitCodegenSettings(
+                "com.example",
+                "smithy.foo",
+                Collections.emptyList(),
+                Collections.emptyList());
+
+        assertEquals("com.example", settings.packageName());
+        assertEquals("smithy.foo", settings.smithyNamespace());
+        assertEquals(Collections.emptyList(), settings.headerLines());
+        assertEquals(Collections.emptyList(), settings.excludeTags());
+    }
+}