Avoid exposing Arced ResolveEndpoint in public API (#2758)

## Motivation and Context
Hides `Arc<dyn ResolveEndpoint>` from public API.

## Description
This PR replaces the occurrences of `Arc<dyn ResolveEndpoint>` with
`SharedEndpointResolver` to not expose bare `Arc`s in the public API.

## Testing
- [x] Passed tests in CI

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates

----

_By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice._

---------

Co-authored-by: Yuki Saito <awsaito@amazon.com>

Author: ysaito1001

CHANGELOG.next.toml

@@ -162,3 +162,9 @@ filter_by_operation_id(plugin, |id| id.absolute() != "namespace#name");
 author = "82marbag"
 references = ["smithy-rs#2678"]
 meta = { "breaking" = true, "tada" = false, "bug" = false }
+
+[[smithy-rs]]
+message = "The occurrences of `Arc<dyn ResolveEndpoint>` have now been replaced with `SharedEndpointResolver` in public APIs."
+references = ["smithy-rs#2758"]
+meta = { "breaking" = true, "tada" = false, "bug" = false, "target" = "client" }
+author = "ysaito1001"

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

@@ -45,6 +45,7 @@ class TimestreamDecorator : ClientCodegenDecorator {
             },
         )
     }
+
     override fun extras(codegenContext: ClientCodegenContext, rustCrate: RustCrate) {
         val endpointDiscovery = InlineAwsDependency.forRustFile(
             "endpoint_discovery",
@@ -87,7 +88,7 @@ class TimestreamDecorator : ClientCodegenDecorator {
                             time
                         )
                         .await?;
-                        new_conf.endpoint_resolver = ::std::sync::Arc::new(resolver);
+                        new_conf.endpoint_resolver = #{SharedEndpointResolver}::new(resolver);
                         Ok((Self::from_conf(new_conf), reloader))
                     }
                 }
@@ -96,6 +97,8 @@ class TimestreamDecorator : ClientCodegenDecorator {
                 "endpoint_discovery" to endpointDiscovery.toType(),
                 "SystemTime" to RuntimeType.std.resolve("time::SystemTime"),
                 "Duration" to RuntimeType.std.resolve("time::Duration"),
+                "SharedEndpointResolver" to RuntimeType.smithyHttp(codegenContext.runtimeConfig)
+                    .resolve("endpoint::SharedEndpointResolver"),
                 "SystemTimeSource" to RuntimeType.smithyAsync(codegenContext.runtimeConfig)
                     .resolve("time::SystemTimeSource"),
                 *Types(codegenContext.runtimeConfig).toArray(),

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

@@ -13,6 +13,7 @@ import software.amazon.smithy.rust.codegen.core.rustlang.Writable
 import software.amazon.smithy.rust.codegen.core.rustlang.rustTemplate
 import software.amazon.smithy.rust.codegen.core.rustlang.writable
 import software.amazon.smithy.rust.codegen.core.smithy.RuntimeType
+import software.amazon.smithy.rust.codegen.core.smithy.RuntimeType.Companion.preludeScope
 
 /**
  * Customization which injects an Endpoints 2.0 Endpoint Resolver into the service config struct
@@ -28,22 +29,25 @@ internal class EndpointConfigCustomization(
 
     override fun section(section: ServiceConfig): Writable {
         return writable {
+            val sharedEndpointResolver = "#{SharedEndpointResolver}<#{Params}>"
             val resolverTrait = "#{SmithyResolver}<#{Params}>"
             val codegenScope = arrayOf(
+                *preludeScope,
+                "SharedEndpointResolver" to types.sharedEndpointResolver,
                 "SmithyResolver" to types.resolveEndpoint,
                 "Params" to typesGenerator.paramsStruct(),
             )
             when (section) {
                 is ServiceConfig.ConfigStruct -> rustTemplate(
-                    "pub (crate) endpoint_resolver: std::sync::Arc<dyn $resolverTrait>,",
+                    "pub (crate) endpoint_resolver: $sharedEndpointResolver,",
                     *codegenScope,
                 )
 
                 is ServiceConfig.ConfigImpl ->
                     rustTemplate(
                         """
                         /// Returns the endpoint resolver.
-                        pub fn endpoint_resolver(&self) -> std::sync::Arc<dyn $resolverTrait> {
+                        pub fn endpoint_resolver(&self) -> $sharedEndpointResolver {
                             self.endpoint_resolver.clone()
                         }
                         """,
@@ -52,7 +56,7 @@ internal class EndpointConfigCustomization(
 
                 is ServiceConfig.BuilderStruct ->
                     rustTemplate(
-                        "endpoint_resolver: Option<std::sync::Arc<dyn $resolverTrait>>,",
+                        "endpoint_resolver: #{Option}<$sharedEndpointResolver>,",
                         *codegenScope,
                     )
 
@@ -99,15 +103,15 @@ internal class EndpointConfigCustomization(
                         /// Sets the endpoint resolver to use when making requests.
                         $defaultResolverDocs
                         pub fn endpoint_resolver(mut self, endpoint_resolver: impl $resolverTrait + 'static) -> Self {
-                            self.endpoint_resolver = Some(std::sync::Arc::new(endpoint_resolver) as _);
+                            self.endpoint_resolver = #{Some}(#{SharedEndpointResolver}::new(endpoint_resolver));
                             self
                         }
 
                         /// Sets the endpoint resolver to use when making requests.
                         ///
                         /// When unset, the client will used a generated endpoint resolver based on the endpoint resolution
                         /// rules for `$moduleUseName`.
-                        pub fn set_endpoint_resolver(&mut self, endpoint_resolver: Option<std::sync::Arc<dyn $resolverTrait>>) -> &mut Self {
+                        pub fn set_endpoint_resolver(&mut self, endpoint_resolver: #{Option}<$sharedEndpointResolver>) -> &mut Self {
                             self.endpoint_resolver = endpoint_resolver;
                             self
                         }
@@ -122,7 +126,7 @@ internal class EndpointConfigCustomization(
                         rustTemplate(
                             """
                             endpoint_resolver: self.endpoint_resolver.unwrap_or_else(||
-                                std::sync::Arc::new(#{DefaultResolver}::new())
+                                #{SharedEndpointResolver}::new(#{DefaultResolver}::new())
                             ),
                             """,
                             *codegenScope,
@@ -150,8 +154,9 @@ internal class EndpointConfigCustomization(
                         // always fail. In the future, this will be changed to an `expect()`
                         rustTemplate(
                             """
-                            endpoint_resolver: self.endpoint_resolver.unwrap_or_else(||std::sync::Arc::new(#{FailingResolver})),
+                            endpoint_resolver: self.endpoint_resolver.unwrap_or_else(||#{SharedEndpointResolver}::new(#{FailingResolver})),
                             """,
+                            *codegenScope,
                             "FailingResolver" to alwaysFailsResolver,
                         )
                     }

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

@@ -169,12 +169,14 @@ class EndpointsDecorator : ClientCodegenDecorator {
             val codegenScope = arrayOf(
                 *RuntimeType.preludeScope,
                 "Params" to typesGenerator.paramsStruct(),
+                "ResolveEndpoint" to types.resolveEndpoint,
                 "ResolveEndpointError" to types.resolveEndpointError,
             )
             return when (section) {
                 is OperationSection.MutateInput -> writable {
                     rustTemplate(
                         """
+                        use #{ResolveEndpoint};
                         let params_result = #{Params}::builder()#{builderFields:W}.build()
                             .map_err(|err| #{ResolveEndpointError}::from_source("could not construct endpoint parameters", err));
                         let (endpoint_result, params) = match params_result {

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

@@ -48,6 +48,7 @@ class Types(runtimeConfig: RuntimeConfig) {
     private val smithyTypesEndpointModule = RuntimeType.smithyTypes(runtimeConfig).resolve("endpoint")
     val smithyHttpEndpointModule = RuntimeType.smithyHttp(runtimeConfig).resolve("endpoint")
     val resolveEndpoint = smithyHttpEndpointModule.resolve("ResolveEndpoint")
+    val sharedEndpointResolver = smithyHttpEndpointModule.resolve("SharedEndpointResolver")
     val smithyEndpoint = smithyTypesEndpointModule.resolve("Endpoint")
     val resolveEndpointError = smithyHttpEndpointModule.resolve("ResolveEndpointError")
 

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

@@ -97,7 +97,6 @@ class ServiceRuntimePluginGenerator(
             "Params" to endpointTypesGenerator.paramsStruct(),
             "ResolveEndpoint" to http.resolve("endpoint::ResolveEndpoint"),
             "RuntimePlugin" to runtimeApi.resolve("client::runtime_plugin::RuntimePlugin"),
-            "SharedEndpointResolver" to http.resolve("endpoint::SharedEndpointResolver"),
             "StaticAuthOptionResolver" to runtimeApi.resolve("client::auth::option_resolver::StaticAuthOptionResolver"),
             "default_connector" to client.resolve("conns::default_connector"),
             "require_connector" to client.resolve("conns::require_connector"),
@@ -134,7 +133,7 @@ class ServiceRuntimePluginGenerator(
                     cfg.set_auth_option_resolver(#{StaticAuthOptionResolver}::new(#{Vec}::new()));
 
                     let endpoint_resolver = #{DefaultEndpointResolver}::<#{Params}>::new(
-                        #{SharedEndpointResolver}::from(self.handle.conf.endpoint_resolver()));
+                        self.handle.conf.endpoint_resolver());
                     cfg.set_endpoint_resolver(endpoint_resolver);
 
                     // TODO(enableNewSmithyRuntime): Use the `store_append` method of ConfigBag to insert classifiers