[Fred1155]

Motivation and Context

For now on the Smithy path, the step that builds the intermediate model passed an empty paginator map and never marked an operation as paginated. So a client generated from a Smithy model had no paginator classes (such as ListThingsIterable and ListThingsPublisher) and no listThingsPaginator(...) client methods.

This PR fills that gap. Smithy describes pagination with the @paginated trait on an operation, for example:

@paginated(inputToken: "nextToken", outputToken: "nextToken", items: "things", pageSize: "maxResults")
operation ListThings { ... }

@paginated covers most paginators, but not everything paginators-1.json can say. In paginators-1.json:

• Tokens: an operation can list several input and output tokens. S3 ListObjectVersions uses KeyMarker and VersionIdMarker.
• Stop condition: an operation can stop on a boolean field (more_results, such as IAM's IsTruncated) rather than on a missing token.
• Result keys: an operation can list several result keys, each of which becomes an item method on the paginator class. CloudWatch DescribeAlarms returns MetricAlarms, CompositeAlarms, and LogAlarms.

@paginated allows one token each way, no stop field, and one items path. For those paginators, this PR adds a codegen trait, software.amazon.awssdk.codegen#paginatorOverride. It carries the paginators-1.json fields on the operation, so the generated paginator stays the same as on the C2J path. It sits alongside the existing Java-only codegen traits and is applied through smithy-build.json, so the service's model.json is not edited. With skip: true, the trait generates no paginator, for an operation that has @paginated but no paginator on the C2J path. We can modify this in the future.

Modifications

1. paginatorOverride trait: the definition in aws-sdk-java-codegen-traits.smithy and the class PaginatorOverrideTrait, registered as a TraitService.
   • The trait is either skip: true alone, or non-empty inputToken and outputToken lists, plus optional resultKey, moreResults, and limitKey.
   • Any other shape fails when the trait is loaded.
2. AddSmithyPaginators: builds the paginator map, keyed by operation name as in paginators-1.json.
   • An operation's paginatorOverride wins.
   • Otherwise @paginated is translated: inputToken and outputToken become single-element lists, items becomes resultKey, and pageSize becomes limitKey.
   • A service-level @paginated fills in members the operation leaves out, as Smithy's PaginatedIndex does.
3. SmithyIntermediateModelBuilder:
   • Passes the paginator map into the intermediate model.
   • Marks an operation as paginated with the same rule the C2J path uses: a paginator exists and has both tokens. The client methods follow this flag and the paginator classes follow the map, so the two stay in agreement.
   • Drops paginators of deprecatedOperations, as the C2J path does.

Not in this PR:

• Waiters: they follow in a separate PR.
• Writing the overrides: generating paginatorOverride entries from a service's paginators-1.json into smithy-build.json belongs with the tool that generates smithy-build.json from customization.config. Until then, a smithy-build.json without the overrides falls back to translating @paginated.

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING document
• Local run of mvn install succeeds
• My code follows the code style of this project
• My change requires a change to the Javadoc documentation
• I have updated the Javadoc documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed
• I have added a changelog entry. Adding a new entry must be accomplished by running the scripts/new-change script and following the instructions. Commit the new file created by the script in .changes/next-release with your changes.
• My change is to implement 1.11 parity feature and I have updated LaunchChangelog

License

• I confirm that this pull request can be released under the Apache 2 license