Fix ServerAdditionalSettings to allow method calls in any order

Previously, calling generateCodegenComments() before other methods would
fail because it returned the parent type. Modified the class to maintain
the correct type throughout method chaining.

Author: Fahad Zubair

codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/testutil/CodegenIntegrationTest.kt

@@ -40,97 +40,73 @@ data class IntegrationTestParams(
  *     model,
  *     IntegrationTestParams(
  *         additionalSettings =
- *             ServerAdditionalSettings.builder()
- *                 .generateCodegenComments()
- *                 .publicConstrainedTypes()
+ *             ServerAdditionalSettings()
+ *                 .generateCodegenComments(true)
+ *                 .publicConstrainedTypes(true)
  *                 .toObjectNode()
  * )),
  * ```
  */
-sealed class AdditionalSettings {
-    abstract fun toObjectNode(): ObjectNode
-
-    abstract class CoreAdditionalSettings protected constructor(val settings: List<AdditionalSettings>) : AdditionalSettings() {
-        override fun toObjectNode(): ObjectNode {
-            val merged =
-                settings.map { it.toObjectNode() }
-                    .reduce { acc, next -> acc.merge(next) }
-
-            return ObjectNode.builder()
-                .withMember("codegen", merged)
-                .build()
-        }
-
-        abstract class Builder<T : CoreAdditionalSettings> : AdditionalSettings() {
-            protected val settings = mutableListOf<AdditionalSettings>()
-
-            fun generateCodegenComments(debugMode: Boolean = true): Builder<T> {
-                settings.add(GenerateCodegenComments(debugMode))
-                return this
-            }
-
-            abstract fun build(): T
-
-            override fun toObjectNode(): ObjectNode = build().toObjectNode()
+open class AdditionalSettings<T : AdditionalSettings<T>> {
+    private val codegenBuilderDelegate =
+        lazy {
+            ObjectNode.builder()
         }
+    private val codegenBuilder: ObjectNode.Builder by codegenBuilderDelegate
 
-        // Core settings that are common to both Servers and Clients should be defined here.
-        data class GenerateCodegenComments(val debugMode: Boolean) : AdditionalSettings() {
-            override fun toObjectNode(): ObjectNode =
-                ObjectNode.builder()
-                    .withMember("debugMode", debugMode)
-                    .build()
+    fun build(): ObjectNode {
+        return if (codegenBuilderDelegate.isInitialized()) {
+            ObjectNode.builder()
+                .withMember("codegen", codegenBuilder.build())
+                .build()
+        } else {
+            ObjectNode.builder().build()
         }
     }
-}
-
-class ClientAdditionalSettings private constructor(settings: List<AdditionalSettings>) :
-    AdditionalSettings.CoreAdditionalSettings(settings) {
-        class Builder : CoreAdditionalSettings.Builder<ClientAdditionalSettings>() {
-            override fun build(): ClientAdditionalSettings = ClientAdditionalSettings(settings)
-        }
 
-        // Additional settings that are specific to client generation should be defined here.
-
-        companion object {
-            fun builder() = Builder()
-        }
+    @Suppress("UNCHECKED_CAST")
+    open fun generateCodegenComments(debugMode: Boolean = true): T {
+        codegenBuilder.withMember("debugMode", debugMode)
+        return this as T
     }
 
-class ServerAdditionalSettings private constructor(settings: List<AdditionalSettings>) :
-    AdditionalSettings.CoreAdditionalSettings(settings) {
-        class Builder : CoreAdditionalSettings.Builder<ServerAdditionalSettings>() {
-            fun publicConstrainedTypes(enabled: Boolean = true): Builder {
-                settings.add(PublicConstrainedTypes(enabled))
-                return this
-            }
+    @Suppress("UNCHECKED_CAST")
+    protected fun withCodegenMember(
+        key: String,
+        value: Boolean,
+    ): T {
+        codegenBuilder.withMember(key, value)
+        return this as T
+    }
 
-            fun addValidationExceptionToConstrainedOperations(enabled: Boolean = true): Builder {
-                settings.add(AddValidationExceptionToConstrainedOperations(enabled))
-                return this
-            }
+    @Suppress("UNCHECKED_CAST")
+    protected fun withCodegenMember(
+        key: String,
+        value: String,
+    ): T {
+        codegenBuilder.withMember(key, value)
+        return this as T
+    }
 
-            override fun build(): ServerAdditionalSettings = ServerAdditionalSettings(settings)
-        }
+    @Suppress("UNCHECKED_CAST")
+    protected fun withCodegenMember(
+        key: String,
+        value: Number,
+    ): T {
+        codegenBuilder.withMember(key, value)
+        return this as T
+    }
+}
 
-        private data class PublicConstrainedTypes(val enabled: Boolean) : AdditionalSettings() {
-            override fun toObjectNode(): ObjectNode =
-                ObjectNode.builder()
-                    .withMember("publicConstrainedTypes", enabled)
-                    .build()
-        }
+class ServerAdditionalSettings : AdditionalSettings<ServerAdditionalSettings>() {
+    fun publicConstrainedTypes(enabled: Boolean = true): ServerAdditionalSettings =
+        withCodegenMember("publicConstrainedTypes", enabled)
 
-        private data class AddValidationExceptionToConstrainedOperations(val enabled: Boolean) : AdditionalSettings() {
-            override fun toObjectNode(): ObjectNode =
-                ObjectNode.builder()
-                    .withMember("addValidationExceptionToConstrainedOperations", enabled)
-                    .build()
-        }
+    fun addValidationExceptionToConstrainedOperations(enabled: Boolean = true) =
+        withCodegenMember("addValidationExceptionToConstrainedOperations", enabled)
 
-        companion object {
-            fun builder() = Builder()
-        }
-    }
+    fun ignoreUnsupportedConstraints() = withCodegenMember("ignoreUnsupportedConstraints", true)
+}
 
 /**
  * Run cargo test on a true, end-to-end, codegen product of a given model.

codegen-server/src/test/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ConstraintsTest.kt

@@ -242,9 +242,9 @@ class ConstraintsTest {
             IntegrationTestParams(
                 service = "test#SampleService",
                 additionalSettings =
-                    ServerAdditionalSettings.builder()
+                    ServerAdditionalSettings()
                         .publicConstrainedTypes(pubConstraints)
-                        .toObjectNode(),
+                        .build(),
                 overrideTestDir = dir,
             ),
             test = test,

codegen-server/src/test/kotlin/software/amazon/smithy/rust/codegen/server/smithy/customizations/AddValidationExceptionToConstrainedOperationsTest.kt

@@ -76,9 +76,10 @@ internal class AddValidationExceptionToConstrainedOperationsTest {
             testModelWithValidationExceptionImported,
             IntegrationTestParams(
                 additionalSettings =
-                    ServerAdditionalSettings.builder()
+                    ServerAdditionalSettings()
+                        .generateCodegenComments(true)
                         .addValidationExceptionToConstrainedOperations()
-                        .toObjectNode(),
+                        .build(),
             ),
         )
     }

codegen-server/src/test/kotlin/software/amazon/smithy/rust/codegen/server/smithy/protocols/serialize/CborConstraintsIntegrationTest.kt

@@ -6,7 +6,6 @@ package software.amazon.smithy.rust.codegen.server.smithy.protocols.serialize
 
 import org.junit.jupiter.api.Test
 import software.amazon.smithy.rust.codegen.core.testutil.IntegrationTestParams
-import software.amazon.smithy.rust.codegen.core.testutil.ServerAdditionalSettings
 import software.amazon.smithy.rust.codegen.server.smithy.ModelProtocol
 import software.amazon.smithy.rust.codegen.server.smithy.loadSmithyConstraintsModelForProtocol
 import software.amazon.smithy.rust.codegen.server.smithy.testutil.serverIntegrationTest
@@ -20,7 +19,6 @@ class CborConstraintsIntegrationTest {
             model,
             IntegrationTestParams(
                 service = serviceShape.toString(),
-                additionalSettings = ServerAdditionalSettings.builder().generateCodegenComments().toObjectNode(),
             ),
         ) { _, _ ->
         }