Do not generate the operation registry when there are no operations

codegen-server-test/build.gradle.kts

@@ -34,6 +34,7 @@ dependencies {
 }
 
 val allCodegenTests = listOf(
+    CodegenTest("com.aws.example#EmptyService", "empty"),
     CodegenTest("com.amazonaws.simple#SimpleService", "simple"),
     CodegenTest("aws.protocoltests.restjson#RestJson", "rest_json"),
     CodegenTest("aws.protocoltests.restjson.validation#RestJsonValidation", "rest_json_validation"),

codegen-server-test/model/empty.smithy

@@ -0,0 +1 @@
+../../codegen-test/model/empty.smithy

codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/generators/ServerOperationHandlerGenerator.kt

@@ -49,6 +49,8 @@ class ServerOperationHandlerGenerator(
     )
 
     fun render(writer: RustWriter) {
+        check(operations.isNotEmpty())
+
         renderHandlerImplementations(writer, false)
         renderHandlerImplementations(writer, true)
     }

codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/generators/ServerOperationRegistryGenerator.kt

@@ -52,6 +52,8 @@ class ServerOperationRegistryGenerator(
     private val operationRegistryBuilderNameWithArguments = "$operationRegistryBuilderName<$genericArguments>"
 
     fun render(writer: RustWriter) {
+        check(operations.isNotEmpty())
+
         renderOperationRegistryStruct(writer)
         renderOperationRegistryBuilderStruct(writer)
         renderOperationRegistryBuilderError(writer)

codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/generators/ServerServiceGenerator.kt

@@ -13,6 +13,7 @@ import software.amazon.smithy.rust.codegen.smithy.RustCrate
 import software.amazon.smithy.rust.codegen.smithy.generators.protocol.ProtocolGenerator
 import software.amazon.smithy.rust.codegen.smithy.generators.protocol.ProtocolSupport
 import software.amazon.smithy.rust.codegen.smithy.protocols.HttpBindingResolver
+import java.util.logging.Logger
 
 /**
  * ServerServiceGenerator
@@ -28,13 +29,20 @@ class ServerServiceGenerator(
     private val context: CodegenContext,
 ) {
     private val index = TopDownIndex.of(context.model)
+    private val logger = Logger.getLogger(javaClass.name)
 
     /**
      * Render Service Specific code. Code will end up in different files via [useShapeWriter]. See `SymbolVisitor.kt`
      * which assigns a symbol location to each shape.
      */
     fun render() {
         val operations = index.getContainedOperations(context.serviceShape).sortedBy { it.id }
+
+        if (operations.isEmpty()) {
+            logger.warning("[rust-server-codegen] There are no operations in the service closure")
+            return
+        }
+
         for (operation in operations) {
             rustCrate.useShapeWriter(operation) { operationWriter ->
                 protocolGenerator.serverRenderOperation(
@@ -52,11 +60,21 @@ class ServerServiceGenerator(
                 }
             }
         }
-        rustCrate.withModule(RustModule.public("operation_handler", "Operation handlers definition and implementation.")) { writer ->
+        rustCrate.withModule(
+            RustModule.public(
+                "operation_handler",
+                "Operation handlers definition and implementation."
+            )
+        ) { writer ->
             ServerOperationHandlerGenerator(context, operations)
                 .render(writer)
         }
-        rustCrate.withModule(RustModule.public("operation_registry", "A registry of your service's operations.")) { writer ->
+        rustCrate.withModule(
+            RustModule.public(
+                "operation_registry",
+                "A registry of your service's operations."
+            )
+        ) { writer ->
             ServerOperationRegistryGenerator(context, httpBindingResolver, operations)
                 .render(writer)
         }

codegen-test/build.gradle.kts

@@ -35,6 +35,7 @@ dependencies {
 }
 
 val allCodegenTests = listOf(
+    CodegenTest("com.aws.example#EmptyService", "empty"),
     CodegenTest("com.amazonaws.simple#SimpleService", "simple"),
     CodegenTest("com.amazonaws.dynamodb#DynamoDB_20120810", "dynamo"),
     CodegenTest("com.amazonaws.ebs#Ebs", "ebs"),

codegen-test/model/empty.smithy

@@ -0,0 +1,10 @@
+$version: "1.0"
+
+namespace com.aws.example
+
+use aws.protocols#restJson1
+
+@restJson1
+service EmptyService {
+    version: "2022-05-06",
+}

codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/generators/ServiceGenerator.kt

@@ -40,7 +40,8 @@ class ServiceGenerator(
      */
     fun render() {
         val operations = index.getContainedOperations(config.serviceShape).sortedBy { it.id }
-        operations.map { operation ->
+
+        for (operation in operations) {
             rustCrate.useShapeWriter(operation) { operationWriter ->
                 rustCrate.useShapeWriter(operation.inputShape(config.model)) { inputWriter ->
                     // Render the operation shape & serializers input `input.rs`

codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/generators/client/FluentClientDecorator.kt

@@ -322,7 +322,7 @@ class FluentClientGenerator(
             """
             ##[derive(Debug)]
             pub(crate) struct Handle#{generics_decl:W} {
-                pub(crate) client: #{client}::Client#{smithy_inst:W},
+                ##[allow(dead_code)] pub(crate) client: #{client}::Client#{smithy_inst:W},
                 pub(crate) conf: crate::Config,
             }