Smithy generator for paginator by kai-ion · Pull Request #3690 · aws/aws-sdk-cpp

kai-ion · 2026-01-13T19:49:52Z

Issue #, if available:

Description of changes:
Smithy-based code generator for paginators

Check all that applies:

Did a review by yourself.
Added proper tests to cover this PR. (If tests are not applicable, explain.)
Checked if this PR is a breaking (APIs have been changed) change.
Checked if this PR will not introduce cross-platform inconsistent behavior.
Checked if this PR would require a ReadMe/Wiki update.

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sbaluja · 2026-01-15T21:50:33Z

...-codegen/src/main/java/com/amazonaws/util/awsclientsmithygenerator/generators/CppWriter.java

+    public CppWriter writeNamespaceClose(String namespace) {
+        write("} // namespace $L", namespace);
+        return this;
+    }


Being a bit nitpicky but Instead of manually opening and closing namespace blocks, why don't we do something like this:

public CppWriter writeNamespaceOpen(String namespace) { writer.openBlock("namespace $L\n{", namespace); return this; }

and the same for writeNamespaceClose, but with writer.closeBlock. Its functionally the exact same (block functions indent/dedent which doesn't matter since we clang format anyway) , but we should try to use these functions when opening/closing blocks

agicquelamz · 2026-01-23T19:22:41Z

tools/code-generation/smithy/codegen/cpp-pagination-codegen/build.gradle.kts

+    implementation("software.amazon.smithy:smithy-aws-traits:1.51.0")
+    implementation("software.amazon.smithy:smithy-waiters:1.51.0")
+    implementation("software.amazon.smithy:smithy-rules-engine:1.51.0")
+    implementation("software.amazon.smithy:smithy-aws-endpoints:1.51.0")


Why do we need this? It's not like we're going to be using smithy based endpoints rule traits right?

Ah, this was from copying the pattern used in our codegen-workshop.
I will refactor the build script to use our existing pattern from smoke-test gen

Smithy actually needs all the above dependencies, in the current set up we are not accepting any unknown traits

agicquelamz · 2026-01-23T19:24:36Z

.../util/awsclientsmithygenerator/generators/pagination/PaginationCompilationTestGenerator.java

+        parser.run();
+    }
+
+    public void render(CppWriter writer) {


Why do we render this from scratch here? It may be ok for this particular test but should we have a more generic test file rendering logic that is not specific to Paginators?

I agree. I can abstract the common parts like header includes, test class structure, and basic compilation test setup into CompilationTestParser as well.

Refactorted the compilation test to have a BaseCompilationGenerator, if its needed we can extend this class for other test rendering logics

sbiscigl · 2026-01-23T21:18:43Z

generated/src/aws-cpp-sdk-s3/include/aws/s3/S3ClientPagination.h

+namespace Aws {
+namespace S3 {
+
+using ListBucketsPaginator =


so lets talk about how we would use this Paginator then. i assume a code example would look something like

const auto s3_client = Aws::MakeShared<S3Client>("alloc-tag"); for (const auto& page: ListBucketsPaginator{s3_client, listReq}) { //... }

when I look at the java documentation i see that paginator construction is a method on the client. i.e.

ListObjectsV2Iterable listRes = s3.listObjectsV2Paginator(listReq); for (S3Object content : listRes.contents()) { //... }

so my question here is why are we doing it differently than java? one of the most common complaints we get is that SDKs have different ergonmics when you switch bettween them.

so why are we creating paginators different than java and not a as a member? what is preventing us from making it a member function?

shouldnt it look something like this?:

S3Client s3_client{}; for (const auto& page: s3_client.ListBucketsPaginator{listReq}) { //... }

…config

…ename reshape priority

…nged shapeutil logic to correctly use the legacy get/set collision rule

Fix pagination traits generator for nested tokens andle explicit nested tokens like "EngineDefaults.Marker" correctly

abbreviation and servicename mismatch

Backward compatibility map for operations that must use "SdkResult" suffix.

S3's ListParts operation has NextPartNumberMarker as integer in C2J but string in Smithy.

…nPlugin to templates

…mber variable tableName

…hods for pagination, and smithy generator to make the base client templates. comment out the integration test. move the model traits into the service model dir instead of pagination dir erated/src/aws-cpp-sdk-bedrock-agentcore-control/include/aws/bedrock-agentcore-control/model/CreateOnlineEvaluationConfigRequest.h

…test adding back removed dependencies and uncommenting dynamo integration test

sbiscigl · 2026-02-05T20:44:23Z

generated/src/aws-cpp-sdk-dynamodb/include/aws/dynamodb/DynamoDBClientPagination.h

+namespace Aws {
+namespace DynamoDB {
+
+using ListContributorInsightsPaginator = Aws::Utils::Pagination::PagePaginator<DynamoDBClient, Model::ListContributorInsightsRequest,


lets change PagePaginator to Paginator, unless you feel strongly about the name

sbiscigl · 2026-02-05T20:48:51Z

generated/src/aws-cpp-sdk-dynamodb/include/aws/dynamodb/model/ScanPaginationTraits.h

+
+namespace Aws {
+namespace DynamoDB {
+class DynamoDBClient;


instead of forward declaring DynamoDB why not have ScanPaginationTraits take a template parameter template <typename Client = ClientType> like you have on Invoke then the entire class is tempalted. You already pass DynamoDBClient as a template parameter in DynamoDBClientPagination.h

sbiscigl · 2026-02-05T20:49:05Z

generated/src/aws-cpp-sdk-dynamodb/include/aws/dynamodb/DynamoDBClient.h

                                              DynamoDBEndpointProviderBase, smithy::client::JsonOutcomeSerializer,
-                                              smithy::client::JsonOutcome, Aws::Client::DynamoDBErrorMarshaller> {
+                                              smithy::client::JsonOutcome, Aws::Client::DynamoDBErrorMarshaller>,
+      public DynamoDBPaginationBase<DynamoDBClient> {


chefs kiss

sbiscigl · 2026-02-05T21:37:23Z

generated/src/aws-cpp-sdk-dynamodb/include/aws/dynamodb/DynamoDBPaginationBase.h

+  ListContributorInsightsPaginator(const Model::ListContributorInsightsRequest& request) {
+    return Aws::Utils::Pagination::PagePaginator<DerivedClient, Model::ListContributorInsightsRequest,
+                                                 Pagination::ListContributorInsightsPaginationTraits>{
+        std::shared_ptr<DerivedClient>(static_cast<DerivedClient*>(this), [](DerivedClient*) {}), request};


std::shared_ptr(static_cast<DerivedClient*>(this), {})

likely isnt what we want to be doing, you are creating a shared point from this then have a custom deleter [](DerivedClient*) {} that does nothing when delete is called. you are essentially trying to fit this into a shared pointer without using the actual properties of shared.

consider

#include <iostream> #include <thread> template<typename crtp_t> class thing { public: thing(crtp_t& ref) : ptr_(ref) {}; void do_something() { ptr_.work(); } private: crtp_t& ptr_; }; template <typename crtp_t> class mixin { public: void operation() { thing<crtp_t> operation_thing{*static_cast<crtp_t*>(this)}; operation_thing.do_something(); } }; class widget : public mixin<widget> { public: void work() { std::cout << "hello from class\n"; } }; auto main() -> int { widget w{}; w.operation(); return 0; }

which is long way of saying on PagePaginator make client a reference not a pointer

sbiscigl · 2026-02-05T21:37:54Z

generated/tests/dynamodb-gen-tests/DynamoDBPaginationCompilationTests.cpp

+
+TEST_F(DynamoDBPaginationCompilationTest, DynamoDBPaginationHeadersCompile)
+{
+        // Test passes if compilation succeeds


chefs kiss

sbiscigl · 2026-02-05T21:40:03Z

tests/aws-cpp-sdk-dynamodb-integration-tests/ScanPaginationIntegrationTest.cpp

+
+class ScanPaginationTest : public Aws::Testing::AwsCppSdkGTestSuite {
+protected:
+    std::shared_ptr<DynamoDBClient> dynamoClient;


nit: why shared pointer and not stack varable?

sbiscigl · 2026-02-05T21:41:05Z

tools/scripts/codegen/legacy_c2j_cpp_gen.py

        print(f"Code generation done, (re)generated {len(done)} packages.")  # Including defaults and partitions

-        # Format generated client code
-        generated_clients = [service for service in self.c2j_models.keys()]


is this not needed in this code path anymore?

sbiscigl · 2026-02-05T21:41:37Z

tools/code-generation/smithy/codegen/smithy2c2j_service_map.json

    "cloudwatch-logs":"logs",
    "directory-service":"ds",
-    "elasticsearch-service ":"es",
+    "elasticsearch-service":"es",


nit: whitespace change

sbiscigl · 2026-02-05T21:45:38Z

...m/amazonaws/util/awsclientsmithygenerator/generators/pagination/PaginationCodegenPlugin.java

+        var model = context.getModel();
+
+        // Handle legacy services without Smithy models
+        if (context.getProjectionName().endsWith(".mock")) {


how is ".mock" generated in the projection name?

sbaluja reviewed Jan 15, 2026

View reviewed changes

kai-ion force-pushed the paginatorModel branch 6 times, most recently from 0fd0691 to 661e748 Compare January 23, 2026 15:24

agicquelamz reviewed Jan 23, 2026

View reviewed changes

sbiscigl reviewed Jan 23, 2026

View reviewed changes

kai-ion force-pushed the paginatorModel branch 6 times, most recently from 20097ca to 7433789 Compare February 3, 2026 18:26

kai-ion added 15 commits February 3, 2026 19:14

Smithy code gen for pagination

da909ca

Smithy code gen for pagination

61824e5

updated parser to use c2j mapping names

4aaac87

updated writer to use c2j mapping names and deleted space in map.json

4074797

fix file location

06b9191

added a compilation test

29d67ab

updated cppwriter to use smithy library

8d52259

changed parsers to be more generic

938db88

added service name util

8b8462b

filter out deprecated service

ecc126a

edgecases for backwards compatibility

58410cd

edgecases for backwards compatibility

1290407

temporary fix for AccessAnalyzer which uses service-level pagination …

e9f866b

…config

temporary fix for amp

f180197

temporary fix for B2BI

e98b05e

kai-ion added 14 commits February 3, 2026 19:14

added a patch to add deadline

13cf71e

added a patch to add transfer to abbreivation list and fix the servic…

53e8658

…ename reshape priority

added a patch to ecr to fix GetLifecyclePolicyPreviewSdkResult.h. cha…

4ea1230

…nged shapeutil logic to correctly use the legacy get/set collision rule

added a patch for elasticache

0ec38e4

Fix pagination traits generator for nested tokens andle explicit nested tokens like "EngineDefaults.Marker" correctly

added a patch for lexv2-models.

345afc3

abbreviation and servicename mismatch

added a patch for medialive

f4e22b5

Backward compatibility map for operations that must use "SdkResult" suffix.

added a patch for s3 list parts where

deb9baf

S3's ListParts operation has NextPartNumberMarker as integer in C2J but string in Smithy.

added integration tests for s3,ec2,dynamodb

2e9ae4d

added a patch to fix std string usage

d20e576

changed variable naming from c2j to smithy and moved paginationCodege…

ecbf152

…nPlugin to templates

refactor code to shapeutil

884f98d

WaitUntilActive method parameter tableName was shadowing the class me…

c4b4337

…mber variable tableName

literally copy bucket integration test

d1370ba

kai-ion force-pushed the paginatorModel branch from feb8542 to 491f11f Compare February 4, 2026 00:15

added a new codegen project for cpp-codegen

bb8aeb7

kai-ion force-pushed the paginatorModel branch from 2e48a84 to bb8aeb7 Compare February 4, 2026 15:50

kai-ion added 4 commits February 4, 2026 10:53

reverted smoke test gen changes back to main

1395993

reverted smoke test gen changes back to main

74dc679

adding generic rendering generators

b409255

adding back removed dependencies and uncommenting dynamo integration …

82dc080

…test adding back removed dependencies and uncommenting dynamo integration test

kai-ion force-pushed the paginatorModel branch 2 times, most recently from 034cc1a to a426d02 Compare February 5, 2026 17:52

kai-ion added 2 commits February 5, 2026 14:30

fixing listobject paginator test

7e8f743

reduce ec2 integration test

03ae46d

kai-ion force-pushed the paginatorModel branch from a426d02 to 03ae46d Compare February 5, 2026 19:49

reduce dynamodb integration test

df76674

sbiscigl reviewed Feb 5, 2026

View reviewed changes

changed region for ec2 integration test

239688c

kai-ion force-pushed the paginatorModel branch from e7a992b to 239688c Compare February 6, 2026 02:46

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kai-ion commented Jan 13, 2026

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sbiscigl Jan 23, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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sbiscigl Jan 23, 2026 •

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