Add decorator and setting to set hints.mostly-unused

.changelog/hints-mostly-unused.md

@@ -0,0 +1,13 @@
+---
+applies_to:
+  - aws-sdk-rust
+  - client
+authors:
+  - landonxjames
+references:
+  - smithy-rs#4208
+breaking: false
+new_feature: true
+bug_fix: false
+---
+Add the ability to add `hints.mostly-unused = true` to Cargo.toml. Also enable this hint for the `aws-sdk-ec2`, `aws-sdk-s3`, and `aws-sdk-dynamodb` crates.

aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/AwsCodegenDecorator.kt

@@ -7,6 +7,8 @@ package software.amazon.smithy.rustsdk
 
 import software.amazon.smithy.rust.codegen.client.smithy.customizations.DocsRsMetadataDecorator
 import software.amazon.smithy.rust.codegen.client.smithy.customizations.DocsRsMetadataSettings
+import software.amazon.smithy.rust.codegen.client.smithy.customizations.ManifestHintsDecorator
+import software.amazon.smithy.rust.codegen.client.smithy.customizations.ManifestHintsSettings
 import software.amazon.smithy.rust.codegen.client.smithy.customize.ClientCodegenDecorator
 import software.amazon.smithy.rust.codegen.client.smithy.customize.CombinedClientCodegenDecorator
 import software.amazon.smithy.rustsdk.customize.AwsDisableStalledStreamProtection
@@ -72,6 +74,11 @@ val DECORATORS: List<ClientCodegenDecorator> =
             Sigv4aAuthTraitBackfillDecorator(),
             EndpointBasedAuthSchemeDecorator(),
             SpanDecorator(),
+            ManifestHintsDecorator(
+                ManifestHintsSettings(
+                    mostlyUnused = true,
+                ),
+            ),
             // TODO(https://github.com/smithy-lang/smithy-rs/issues/3863): Comment in once the issue has been resolved
             // SmokeTestsDecorator(),
         ),

aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/ServiceSpecificDecorator.kt

@@ -17,6 +17,14 @@ fun ClientCodegenDecorator.onlyApplyTo(serviceId: String): List<ClientCodegenDec
         },
     )
 
+/** Only apply this decorator to the given list of service IDs */
+fun ClientCodegenDecorator.onlyApplyToList(serviceIds: List<String>): List<ClientCodegenDecorator> =
+    serviceIds.map {
+        ConditionalDecorator(this) { _, serviceShapeId ->
+            serviceShapeId == ShapeId.from(it)
+        }
+    }
+
 /** Apply this decorator to all services but the one identified by ID */
 fun ClientCodegenDecorator.applyExceptFor(serviceId: String): List<ClientCodegenDecorator> =
     listOf(

aws/sdk/build.gradle.kts

@@ -74,6 +74,13 @@ fun loadServiceMembership(): Membership {
     return membershipOverride ?: fullSdk
 }
 
+val hintMostlyUnusedList: Set<String> by lazy { hintMostlyUnusedList() }
+
+fun hintMostlyUnusedList(): Set<String> {
+    val list = properties.get("aws.services.hints.mostlyUnused") ?: ""
+    return list.split(",").map { it.trim() }.toSet()
+}
+
 fun generateSmithyBuild(services: AwsServices): String {
     val awsConfigVersion = properties.get(CrateSet.STABLE_VERSION_PROP_NAME)
         ?: throw IllegalStateException("missing ${CrateSet.STABLE_VERSION_PROP_NAME} for aws-config version")
@@ -92,6 +99,7 @@ fun generateSmithyBuild(services: AwsServices): String {
             services.partitionsConfigPath.let { software.amazon.smithy.utils.StringUtils.escapeJavaString(it, "") }
         val integrationTestPath = project.projectDir.resolve("integration-tests")
             .let { software.amazon.smithy.utils.StringUtils.escapeJavaString(it, "") }
+        val hintMostlyUnusedListMembers = hintMostlyUnusedList.joinToString(", ") { "\"$it\"" }
         """
             "${service.module}": {
                 "imports": [${files.joinToString()}],
@@ -118,6 +126,7 @@ fun generateSmithyBuild(services: AwsServices): String {
                         "moduleRepository": "https://github.com/awslabs/aws-sdk-rust",
                         "license": "Apache-2.0",
                         "minimumSupportedRustVersion": "${getRustMSRV()}",
+                        "hintMostlyUnusedList": [$hintMostlyUnusedListMembers],
                         "customizationConfig": {
                             "awsSdk": {
                                 "awsSdkBuild": true,
@@ -148,6 +157,7 @@ fun generateSmithyBuild(services: AwsServices): String {
 tasks.register("generateSmithyBuild") {
     description = "generate smithy-build.json"
     inputs.property("servicelist", awsServices.services.toString())
+    inputs.property("hintMostlyUnusedList", hintMostlyUnusedList)
     inputs.dir(projectDir.resolve("aws-models"))
     outputs.file(layout.buildDirectory.file("smithy-build.json"))
 
@@ -494,8 +504,8 @@ fun Project.registerDowngradeFor(
             val crateNameToLastKnownWorkingVersions =
                 mapOf(
                     "minicbor" to "0.24.2",
-                    "libfuzzer-sys" to "0.4.7" // TODO(https://github.com/rust-fuzz/libfuzzer/issues/126)
-                    )
+                    "libfuzzer-sys" to "0.4.7", // TODO(https://github.com/rust-fuzz/libfuzzer/issues/126)
+                )
 
             crateNameToLastKnownWorkingVersions.forEach { (crate, version) ->
                 // doesn't matter even if the specified crate does not exist in the lockfile

aws/sdk/gradle.properties

@@ -2,5 +2,12 @@
 # Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 # SPDX-License-Identifier: Apache-2.0
 #
-
 aws.services=
+aws.services.hints.mostlyUnused=\
+  aws-sd-cloudformation,\
+  aws-sdk-dynamodb,\
+  aws-sdk-ec2,\
+  aws-sdk-s3,\
+  aws-sdk-sns,\
+  aws-sdk-sqs,\
+  aws-sdk-ssm

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

@@ -38,6 +38,7 @@ data class ClientRustSettings(
     override val examplesUri: String?,
     override val minimumSupportedRustVersion: String? = null,
     override val customizationConfig: ObjectNode?,
+    override val hintMostlyUnusedList: List<String>,
 ) : CoreRustSettings(
         service,
         moduleName,
@@ -51,6 +52,7 @@ data class ClientRustSettings(
         examplesUri,
         minimumSupportedRustVersion,
         customizationConfig,
+        hintMostlyUnusedList,
     ) {
     companion object {
         fun from(
@@ -73,6 +75,7 @@ data class ClientRustSettings(
                 examplesUri = coreRustSettings.examplesUri,
                 minimumSupportedRustVersion = coreRustSettings.minimumSupportedRustVersion,
                 customizationConfig = coreRustSettings.customizationConfig,
+                hintMostlyUnusedList = coreRustSettings.hintMostlyUnusedList,
             )
         }
     }
@@ -115,14 +118,29 @@ data class ClientCodegenConfig(
         ) = if (node.isPresent) {
             ClientCodegenConfig(
                 formatTimeoutSeconds = coreCodegenConfig.formatTimeoutSeconds,
-                flattenCollectionAccessors = node.get().getBooleanMemberOrDefault("flattenCollectionAccessors", DEFAULT_FLATTEN_ACCESSORS),
+                flattenCollectionAccessors =
+                    node.get()
+                        .getBooleanMemberOrDefault("flattenCollectionAccessors", DEFAULT_FLATTEN_ACCESSORS),
                 debugMode = coreCodegenConfig.debugMode,
                 renameExceptions = node.get().getBooleanMemberOrDefault("renameErrors", DEFAULT_RENAME_EXCEPTIONS),
-                includeFluentClient = node.get().getBooleanMemberOrDefault("includeFluentClient", DEFAULT_INCLUDE_FLUENT_CLIENT),
-                addMessageToErrors = node.get().getBooleanMemberOrDefault("addMessageToErrors", DEFAULT_ADD_MESSAGE_TO_ERRORS),
-                includeEndpointUrlConfig = node.get().getBooleanMemberOrDefault("includeEndpointUrlConfig", DEFAULT_INCLUDE_ENDPOINT_URL_CONFIG),
-                enableUserConfigurableRuntimePlugins = node.get().getBooleanMemberOrDefault("enableUserConfigurableRuntimePlugins", DEFAULT_ENABLE_USER_CONFIGURABLE_RUNTIME_PLUGINS),
-                nullabilityCheckMode = NullableIndex.CheckMode.valueOf(node.get().getStringMemberOrDefault("nullabilityCheckMode", DEFAULT_NULLABILITY_CHECK_MODE)),
+                includeFluentClient =
+                    node.get()
+                        .getBooleanMemberOrDefault("includeFluentClient", DEFAULT_INCLUDE_FLUENT_CLIENT),
+                addMessageToErrors =
+                    node.get()
+                        .getBooleanMemberOrDefault("addMessageToErrors", DEFAULT_ADD_MESSAGE_TO_ERRORS),
+                includeEndpointUrlConfig =
+                    node.get()
+                        .getBooleanMemberOrDefault("includeEndpointUrlConfig", DEFAULT_INCLUDE_ENDPOINT_URL_CONFIG),
+                enableUserConfigurableRuntimePlugins =
+                    node.get().getBooleanMemberOrDefault(
+                        "enableUserConfigurableRuntimePlugins",
+                        DEFAULT_ENABLE_USER_CONFIGURABLE_RUNTIME_PLUGINS,
+                    ),
+                nullabilityCheckMode =
+                    NullableIndex.CheckMode.valueOf(
+                        node.get().getStringMemberOrDefault("nullabilityCheckMode", DEFAULT_NULLABILITY_CHECK_MODE),
+                    ),
             )
         } else {
             ClientCodegenConfig(

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

@@ -0,0 +1,44 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.rust.codegen.client.smithy.customizations
+
+import software.amazon.smithy.rust.codegen.client.smithy.ClientCodegenContext
+import software.amazon.smithy.rust.codegen.client.smithy.customize.ClientCodegenDecorator
+import software.amazon.smithy.rust.codegen.core.smithy.generators.ManifestCustomizations
+
+/**
+ * See https://blog.rust-lang.org/inside-rust/2025/07/15/call-for-testing-hint-mostly-unused/ for more information
+ */
+data class ManifestHintsSettings(
+    val mostlyUnused: Boolean? = null,
+)
+
+fun ManifestHintsSettings.asMap(): Map<String, Any> {
+    val inner =
+        listOfNotNull(
+            mostlyUnused?.let { "mostly-unused" to it },
+        ).toMap()
+    return mapOf("hints" to inner)
+}
+
+/**
+ * Write compilation hints metdata settings into Cargo.toml
+ *
+ * # Notes
+ * This decorator is not used by default, code generators must manually configure and include it in their builds.
+ */
+class ManifestHintsDecorator(private val manifestHintsSettings: ManifestHintsSettings) : ClientCodegenDecorator {
+    override val name: String = "ManifestHintsDecorator"
+    override val order: Byte = 0
+
+    override fun crateManifestCustomizations(codegenContext: ClientCodegenContext): ManifestCustomizations {
+        if (codegenContext.settings.hintMostlyUnusedList.contains(codegenContext.settings.moduleName)) {
+            return manifestHintsSettings.asMap()
+        } else {
+            return emptyMap()
+        }
+    }
+}

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

@@ -38,6 +38,7 @@ fun testClientRustSettings(
     examplesUri: String? = null,
     minimumSupportedRustVersion: String? = null,
     customizationConfig: ObjectNode? = null,
+    hintMostlyUnusedList: List<String> = emptyList(),
 ) = ClientRustSettings(
     service,
     moduleName,
@@ -51,6 +52,7 @@ fun testClientRustSettings(
     examplesUri,
     minimumSupportedRustVersion,
     customizationConfig,
+    hintMostlyUnusedList,
 )
 
 val TestClientRustSymbolProviderConfig =

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

@@ -15,6 +15,7 @@ import software.amazon.smithy.model.shapes.ShapeId
 import software.amazon.smithy.rust.codegen.core.util.orNull
 import java.util.Optional
 import java.util.logging.Logger
+import kotlin.jvm.optionals.getOrElse
 import kotlin.streams.toList
 
 private const val SERVICE = "service"
@@ -29,6 +30,7 @@ private const val EXAMPLES = "examples"
 private const val MINIMUM_SUPPORTED_RUST_VERSION = "minimumSupportedRustVersion"
 private const val CUSTOMIZATION_CONFIG = "customizationConfig"
 const val CODEGEN_SETTINGS = "codegen"
+private const val HINT_MOSTLY_UNUSED_LIST = "hintMostlyUnusedList"
 
 /**
  * [CoreCodegenConfig] contains code-generation configuration that is _common to all_  smithy-rs plugins.
@@ -52,9 +54,13 @@ open class CoreCodegenConfig(
         fun fromNode(node: Optional<ObjectNode>): CoreCodegenConfig =
             if (node.isPresent) {
                 CoreCodegenConfig(
-                    formatTimeoutSeconds = node.get().getNumberMemberOrDefault("formatTimeoutSeconds", DEFAULT_FORMAT_TIMEOUT_SECONDS).toInt(),
+                    formatTimeoutSeconds =
+                        node.get()
+                            .getNumberMemberOrDefault("formatTimeoutSeconds", DEFAULT_FORMAT_TIMEOUT_SECONDS).toInt(),
                     debugMode = node.get().getBooleanMemberOrDefault("debugMode", DEFAULT_DEBUG_MODE),
-                    flattenCollectionAccessors = node.get().getBooleanMemberOrDefault("flattenCollectionAccessors", DEFAULT_FLATTEN_MODE),
+                    flattenCollectionAccessors =
+                        node.get()
+                            .getBooleanMemberOrDefault("flattenCollectionAccessors", DEFAULT_FLATTEN_MODE),
                 )
             } else {
                 CoreCodegenConfig(
@@ -91,6 +97,7 @@ open class CoreRustSettings(
     open val examplesUri: String? = null,
     open val minimumSupportedRustVersion: String? = null,
     open val customizationConfig: ObjectNode? = null,
+    open val hintMostlyUnusedList: List<String> = emptyList(),
 ) {
     /**
      * Get the corresponding [ServiceShape] from a model.
@@ -123,12 +130,14 @@ open class CoreRustSettings(
                             "contain any service shapes",
                     )
                 }
+
                 services.size > 1 -> {
                     throw CodegenException(
                         "Cannot infer service to generate because the model contains " +
                             "multiple service shapes: " + services,
                     )
                 }
+
                 else -> {
                     val service = services[0]
                     LOGGER.info("Inferring service to generate as: $service")
@@ -180,6 +189,7 @@ open class CoreRustSettings(
                     LICENSE,
                     MINIMUM_SUPPORTED_RUST_VERSION,
                     CUSTOMIZATION_CONFIG,
+                    HINT_MOSTLY_UNUSED_LIST,
                 ),
             )
 
@@ -202,6 +212,14 @@ open class CoreRustSettings(
                 examplesUri = config.getStringMember(EXAMPLES).orNull()?.value,
                 minimumSupportedRustVersion = config.getStringMember(MINIMUM_SUPPORTED_RUST_VERSION).orNull()?.value,
                 customizationConfig = config.getObjectMember(CUSTOMIZATION_CONFIG).orNull(),
+                hintMostlyUnusedList =
+                    config.getArrayMember("hintMostlyUnusedList").map {
+                        it.elements.mapNotNull { node ->
+                            node.asStringNode().map { stringNode ->
+                                stringNode.value
+                            }.orNull()
+                        }
+                    }.getOrElse { emptyList() },
             )
         }
     }

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

@@ -1,4 +1,3 @@
-
 /*
  * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
  * SPDX-License-Identifier: Apache-2.0
@@ -83,8 +82,15 @@ class TsServerCodegenVisitor(
             publicConstrainedTypes: Boolean,
             includeConstraintShapeProvider: Boolean,
             codegenDecorator: ServerCodegenDecorator,
-        ) =
-            RustServerCodegenTsPlugin.baseSymbolProvider(settings, model, serviceShape, rustSymbolProviderConfig, publicConstrainedTypes, includeConstraintShapeProvider, codegenDecorator)
+        ) = RustServerCodegenTsPlugin.baseSymbolProvider(
+            settings,
+            model,
+            serviceShape,
+            rustSymbolProviderConfig,
+            publicConstrainedTypes,
+            includeConstraintShapeProvider,
+            codegenDecorator,
+        )
 
         val serverSymbolProviders =
             ServerSymbolProviders.from(
@@ -171,7 +177,7 @@ class TsServerCodegenVisitor(
         fun tsServerEnumGeneratorFactory(
             codegenContext: ServerCodegenContext,
             shape: StringShape,
-        ) = TsServerEnumGenerator(codegenContext, shape, validationExceptionConversionGenerator)
+        ) = TsServerEnumGenerator(codegenContext, shape, validationExceptionConversionGenerator, emptyList())
         stringShape(shape, ::tsServerEnumGeneratorFactory)
     }
 

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

@@ -10,6 +10,7 @@ import software.amazon.smithy.rust.codegen.core.rustlang.Attribute
 import software.amazon.smithy.rust.codegen.core.rustlang.Writable
 import software.amazon.smithy.rust.codegen.core.rustlang.rust
 import software.amazon.smithy.rust.codegen.core.rustlang.writable
+import software.amazon.smithy.rust.codegen.core.smithy.generators.EnumCustomization
 import software.amazon.smithy.rust.codegen.core.smithy.generators.EnumGenerator
 import software.amazon.smithy.rust.codegen.core.smithy.generators.EnumGeneratorContext
 import software.amazon.smithy.rust.codegen.server.smithy.ServerCodegenContext
@@ -41,6 +42,7 @@ class TsServerEnumGenerator(
     codegenContext: ServerCodegenContext,
     shape: StringShape,
     validationExceptionConversionGenerator: ValidationExceptionConversionGenerator,
+    customizations: List<EnumCustomization>,
 ) : EnumGenerator(
         codegenContext.model,
         codegenContext.symbolProvider,
@@ -50,4 +52,5 @@ class TsServerEnumGenerator(
             shape,
             validationExceptionConversionGenerator,
         ),
+        customizations,
     )