Do not generate public empty modules

CHANGELOG.next.toml

@@ -10,6 +10,16 @@
 # references = ["smithy-rs#920"]
 # meta = { "breaking" = false, "tada" = false, "bug" = false, "target" = "client | server | all"}
 # author = "rcoh"
+
+[[smithy-rs]]
+message = """
+Mark `operation` and `operation_handler` modules as private in the generated server crate.
+Both modules did not contain any public types, therefore there should be no actual breakage when updating.
+"""
+references = ["smithy-rs#1803"]
+meta = { "breaking" = true, "tada" = false, "bug" = false, "target" = "server"}
+author = "LukeMathWalker"
+
 [[smithy-rs]]
 message = "Pokémon Service example code now runs clippy during build."
 references = ["smithy-rs#1727"]

codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/CodegenVisitor.kt

@@ -23,7 +23,8 @@ import software.amazon.smithy.rust.codegen.client.smithy.generators.protocol.Cli
 import software.amazon.smithy.rust.codegen.client.smithy.protocols.ClientProtocolLoader
 import software.amazon.smithy.rust.codegen.client.smithy.transformers.AddErrorMessage
 import software.amazon.smithy.rust.codegen.client.smithy.transformers.RemoveEventStreamOperations
-import software.amazon.smithy.rust.codegen.core.smithy.DefaultPublicModules
+import software.amazon.smithy.rust.codegen.core.rustlang.RustModule
+import software.amazon.smithy.rust.codegen.core.rustlang.Visibility
 import software.amazon.smithy.rust.codegen.core.smithy.RustCrate
 import software.amazon.smithy.rust.codegen.core.smithy.RustSymbolProvider
 import software.amazon.smithy.rust.codegen.core.smithy.SymbolVisitorConfig
@@ -81,10 +82,19 @@ class CodegenVisitor(
         symbolProvider = RustCodegenPlugin.baseSymbolProvider(model, service, symbolVisitorConfig)
 
         codegenContext = ClientCodegenContext(model, symbolProvider, service, protocol, settings)
+
+        val clientPublicModules = setOf(
+            RustModule.Error,
+            RustModule.Model,
+            RustModule.Input,
+            RustModule.Output,
+            RustModule.Config,
+            RustModule.operation(Visibility.PUBLIC),
+        ).associateBy { it.name }
         rustCrate = RustCrate(
             context.fileManifest,
             symbolProvider,
-            DefaultPublicModules,
+            clientPublicModules,
             codegenContext.settings.codegenConfig,
         )
         protocolGenerator = protocolGeneratorFactory.buildProtocolGenerator(codegenContext)

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

@@ -10,6 +10,7 @@ import software.amazon.smithy.rust.codegen.core.rustlang.GenericTypeArg
 import software.amazon.smithy.rust.codegen.core.rustlang.RustGenerics
 import software.amazon.smithy.rust.codegen.core.rustlang.RustModule
 import software.amazon.smithy.rust.codegen.core.rustlang.RustWriter
+import software.amazon.smithy.rust.codegen.core.rustlang.Visibility
 import software.amazon.smithy.rust.codegen.core.rustlang.asType
 import software.amazon.smithy.rust.codegen.core.rustlang.docs
 import software.amazon.smithy.rust.codegen.core.rustlang.rust
@@ -34,7 +35,7 @@ class CustomizableOperationGenerator(
     private val smithyTypes = CargoDependency.SmithyTypes(runtimeConfig).asType()
 
     fun render(crate: RustCrate) {
-        crate.withModule(RustModule.Operation) { writer ->
+        crate.withModule(RustModule.operation(Visibility.PUBLIC)) { writer ->
             writer.docs("Operation customization and supporting types")
             writer.rust("pub mod customize;")
         }

codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/rustlang/RustModule.kt

@@ -23,8 +23,18 @@ data class RustModule(val name: String, val rustMetadata: RustMetadata, val docu
         fun private(name: String, documentation: String? = null): RustModule =
             default(name, visibility = Visibility.PRIVATE, documentation = documentation)
 
+        /* Common modules used across client, server and tests */
         val Config = public("config", documentation = "Configuration for the service.")
         val Error = public("error", documentation = "All error types that operations can return.")
-        val Operation = public("operation", documentation = "All operations that this crate can perform.")
+        val Model = public("model", documentation = "Data structures used by operation inputs/outputs.")
+        val Input = public("input", documentation = "Input structures for operations.")
+        val Output = public("output", documentation = "Output structures for operations.")
+
+        /**
+         * Helper method to generate the `operation` Rust module.
+         * Its visibility depends on the generation context (client or server).
+         */
+        fun operation(visibility: Visibility): RustModule =
+            default("operation", visibility = visibility, documentation = "All operations that this crate can perform.")
     }
 }

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

@@ -170,18 +170,6 @@ open class RustCrate(
     }
 }
 
-/**
- * Allowlist of modules that will be exposed publicly in generated crates
- */
-val DefaultPublicModules = setOf(
-    RustModule.Error,
-    RustModule.Operation,
-    RustModule.public("model", documentation = "Data structures used by operation inputs/outputs."),
-    RustModule.public("input", documentation = "Input structures for operations."),
-    RustModule.public("output", documentation = "Output structures for operations."),
-    RustModule.Config,
-).associateBy { it.name }
-
 /**
  * Finalize all the writers by:
  * - inlining inline dependencies that have been used

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

@@ -18,11 +18,11 @@ import software.amazon.smithy.model.shapes.ShapeId
 import software.amazon.smithy.model.traits.EnumDefinition
 import software.amazon.smithy.rust.codegen.core.rustlang.CargoDependency
 import software.amazon.smithy.rust.codegen.core.rustlang.RustDependency
+import software.amazon.smithy.rust.codegen.core.rustlang.RustModule
 import software.amazon.smithy.rust.codegen.core.rustlang.RustWriter
 import software.amazon.smithy.rust.codegen.core.rustlang.raw
 import software.amazon.smithy.rust.codegen.core.rustlang.rustBlock
 import software.amazon.smithy.rust.codegen.core.smithy.CoreCodegenConfig
-import software.amazon.smithy.rust.codegen.core.smithy.DefaultPublicModules
 import software.amazon.smithy.rust.codegen.core.smithy.MaybeRenamed
 import software.amazon.smithy.rust.codegen.core.smithy.RuntimeConfig
 import software.amazon.smithy.rust.codegen.core.smithy.RustCrate
@@ -189,6 +189,14 @@ fun RustWriter.unitTest(
     return rustBlock("fn $name()", *args, block = block)
 }
 
+val DefaultTestPublicModules = setOf(
+    RustModule.Error,
+    RustModule.Model,
+    RustModule.Input,
+    RustModule.Output,
+    RustModule.Config,
+).associateBy { it.name }
+
 /**
  * WriterDelegator used for test purposes
  *
@@ -199,7 +207,12 @@ class TestWriterDelegator(
     symbolProvider: RustSymbolProvider,
     val codegenConfig: CoreCodegenConfig,
 ) :
-    RustCrate(fileManifest, symbolProvider, DefaultPublicModules, codegenConfig) {
+    RustCrate(
+        fileManifest,
+        symbolProvider,
+        DefaultTestPublicModules,
+        codegenConfig,
+    ) {
     val baseDir: Path = fileManifest.baseDir
 
     fun generatedFiles(): List<Path> = fileManifest.files.toList().sorted()

codegen-core/src/test/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/error/TopLevelErrorGeneratorTest.kt

@@ -13,9 +13,9 @@ import software.amazon.smithy.rust.codegen.core.rustlang.rust
 import software.amazon.smithy.rust.codegen.core.smithy.CodegenContext
 import software.amazon.smithy.rust.codegen.core.smithy.CodegenTarget
 import software.amazon.smithy.rust.codegen.core.smithy.CoreRustSettings
-import software.amazon.smithy.rust.codegen.core.smithy.DefaultPublicModules
 import software.amazon.smithy.rust.codegen.core.smithy.RustCrate
 import software.amazon.smithy.rust.codegen.core.smithy.generators.StructureGenerator
+import software.amazon.smithy.rust.codegen.core.testutil.DefaultTestPublicModules
 import software.amazon.smithy.rust.codegen.core.testutil.asSmithyModel
 import software.amazon.smithy.rust.codegen.core.testutil.generatePluginContext
 import software.amazon.smithy.rust.codegen.core.testutil.testSymbolProvider
@@ -75,7 +75,7 @@ internal class TopLevelErrorGeneratorTest {
         val rustCrate = RustCrate(
             pluginContext.fileManifest,
             symbolProvider,
-            DefaultPublicModules,
+            DefaultTestPublicModules,
             codegenContext.settings.codegenConfig,
         )
 

codegen-server/python/src/main/kotlin/software/amazon/smithy/rust/codegen/server/python/smithy/PythonServerCodegenVisitor.kt

@@ -16,7 +16,6 @@ import software.amazon.smithy.model.shapes.UnionShape
 import software.amazon.smithy.model.traits.EnumTrait
 import software.amazon.smithy.rust.codegen.client.smithy.customize.RustCodegenDecorator
 import software.amazon.smithy.rust.codegen.core.smithy.CodegenTarget
-import software.amazon.smithy.rust.codegen.core.smithy.DefaultPublicModules
 import software.amazon.smithy.rust.codegen.core.smithy.RustCrate
 import software.amazon.smithy.rust.codegen.core.smithy.SymbolVisitorConfig
 import software.amazon.smithy.rust.codegen.core.smithy.generators.BuilderGenerator
@@ -25,6 +24,7 @@ import software.amazon.smithy.rust.codegen.core.util.getTrait
 import software.amazon.smithy.rust.codegen.server.python.smithy.generators.PythonServerEnumGenerator
 import software.amazon.smithy.rust.codegen.server.python.smithy.generators.PythonServerServiceGenerator
 import software.amazon.smithy.rust.codegen.server.python.smithy.generators.PythonServerStructureGenerator
+import software.amazon.smithy.rust.codegen.server.smithy.DefaultServerPublicModules
 import software.amazon.smithy.rust.codegen.server.smithy.ServerCodegenContext
 import software.amazon.smithy.rust.codegen.server.smithy.ServerCodegenVisitor
 import software.amazon.smithy.rust.codegen.server.smithy.generators.protocol.ServerProtocol
@@ -69,7 +69,7 @@ class PythonServerCodegenVisitor(
         codegenContext = ServerCodegenContext(model, symbolProvider, service, protocol, settings)
 
         // Override `rustCrate` which carries the symbolProvider.
-        rustCrate = RustCrate(context.fileManifest, symbolProvider, DefaultPublicModules, settings.codegenConfig)
+        rustCrate = RustCrate(context.fileManifest, symbolProvider, DefaultServerPublicModules, settings.codegenConfig)
         // Override `protocolGenerator` which carries the symbolProvider.
         protocolGenerator = protocolGeneratorFactory.buildProtocolGenerator(codegenContext)
     }

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

@@ -18,9 +18,9 @@ import software.amazon.smithy.model.shapes.UnionShape
 import software.amazon.smithy.model.traits.EnumTrait
 import software.amazon.smithy.model.transform.ModelTransformer
 import software.amazon.smithy.rust.codegen.client.smithy.customize.RustCodegenDecorator
+import software.amazon.smithy.rust.codegen.core.rustlang.RustModule
 import software.amazon.smithy.rust.codegen.core.smithy.CodegenTarget
 import software.amazon.smithy.rust.codegen.core.smithy.CoreRustSettings
-import software.amazon.smithy.rust.codegen.core.smithy.DefaultPublicModules
 import software.amazon.smithy.rust.codegen.core.smithy.RustCrate
 import software.amazon.smithy.rust.codegen.core.smithy.RustSymbolProvider
 import software.amazon.smithy.rust.codegen.core.smithy.SymbolVisitorConfig
@@ -42,6 +42,14 @@ import software.amazon.smithy.rust.codegen.server.smithy.generators.protocol.Ser
 import software.amazon.smithy.rust.codegen.server.smithy.protocols.ServerProtocolLoader
 import java.util.logging.Logger
 
+val DefaultServerPublicModules = setOf(
+    RustModule.Error,
+    RustModule.Model,
+    RustModule.Input,
+    RustModule.Output,
+    RustModule.Config,
+).associateBy { it.name }
+
 /**
  * Entrypoint for server-side code generation. This class will walk the in-memory model and
  * generate all the needed types by calling the accept() function on the available shapes.
@@ -92,7 +100,7 @@ open class ServerCodegenVisitor(
             settings,
         )
 
-        rustCrate = RustCrate(context.fileManifest, symbolProvider, DefaultPublicModules, settings.codegenConfig)
+        rustCrate = RustCrate(context.fileManifest, symbolProvider, DefaultServerPublicModules, settings.codegenConfig)
         protocolGenerator = protocolGeneratorFactory.buildProtocolGenerator(codegenContext)
     }
 

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

@@ -13,7 +13,6 @@ import software.amazon.smithy.rust.codegen.core.rustlang.RustModule
 import software.amazon.smithy.rust.codegen.core.rustlang.RustWriter
 import software.amazon.smithy.rust.codegen.core.rustlang.Visibility
 import software.amazon.smithy.rust.codegen.core.smithy.CodegenContext
-import software.amazon.smithy.rust.codegen.core.smithy.DefaultPublicModules
 import software.amazon.smithy.rust.codegen.core.smithy.RustCrate
 import software.amazon.smithy.rust.codegen.core.smithy.generators.protocol.ProtocolSupport
 import software.amazon.smithy.rust.codegen.server.smithy.generators.protocol.ServerProtocol
@@ -41,7 +40,7 @@ open class ServerServiceGenerator(
      * which assigns a symbol location to each shape.
      */
     fun render() {
-        rustCrate.withModule(DefaultPublicModules["operation"]!!) { writer ->
+        rustCrate.withModule(RustModule.operation(Visibility.PRIVATE)) { writer ->
             ServerProtocolTestGenerator(codegenContext, protocolSupport, protocolGenerator).render(writer)
         }
 
@@ -52,7 +51,7 @@ open class ServerServiceGenerator(
                 }
             }
         }
-        rustCrate.withModule(RustModule.public("operation_handler", "Operation handlers definition and implementation.")) { writer ->
+        rustCrate.withModule(RustModule.private("operation_handler", "Operation handlers definition and implementation.")) { writer ->
             renderOperationHandler(writer, operations)
         }
         rustCrate.withModule(