The idea behind this PR is the fact that currently when page, size, sort are substituted with Pageable, then the default values for page, size, sort are lost and Pageable defaults to global spring defaults (size = 10; page = 0). The native spring annotation @PageableDefault makes it possible to respect the defaults specified in the api spec. Native spring annotation @SortDefault.SortDefaults(...) on the other hand preserves the sort default value if it exists.

Another issue stemming from conversion of page, size, sort to Pageableis the loss of query param validations. This PR implements two custom validators (@ValidPageable and @ValidSort) that verify the validity of the passed values and fail if the values are out of spec. These validators should be easily replaceable with custom implementations via importMapping - this might be useful if one has some non-standard sort params and wants to handle the validation in a specific way.

So all together this PR makes sure that the convenience provided by conversion from separate query params page, size, sort to Pageable does not result in less strict contract in the generated api.

Some of the logic is extracted to separate class on purpose. Since I would like to implement this also in java-spring generator for feature parity.

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Summary by cubic

Adds enum-based sort and page/size limit validation for Pageable in kotlin-spring (spring-boot) by generating @ValidSort and @ValidPageable and applying them to paginated operations. Also adds @PageableDefault(page = 0, size = 20) to Pageable params when no explicit page/size are defined, with samples and CI updated.

• New Features

  • New options generateSortValidation and generatePageableConstraintValidation (requires beanValidations=true and library=spring-boot) to generate ValidSort.kt and ValidPageable.kt in configPackage.
  • Detects paginated operations (x-spring-paginated: true or via autoXSpringPaginated) and adds:
    • @PageableDefault(page = 0, size = 20) when Pageable is injected without explicit page/size parameters.
    • @ValidSort(allowedValues=[...]) when sort has inline or $ref enum values.
    • @ValidPageable(maxSize=..., maxPage=...) from size/page parameter maximum values; skipped if not set.
  • Added templates kotlin-spring/validSort.mustache and kotlin-spring/validPageable.mustache, test spec petstore-sort-validation.yaml, generator tests (including page and size limit cases), and a sample at samples/server/petstore/kotlin-springboot-sort-validation; CI runs it.

• Migration

  • Enable with generateSortValidation: "true" and/or generatePageableConstraintValidation: "true", plus beanValidations: "true" and library: spring-boot (optionally autoXSpringPaginated: "true").
  • ValidSort.kt and ValidPageable.kt are generated under your configPackage.
  • @PageableDefault(page = 0, size = 20) is now added automatically for paginated operations without explicit page/size.
  • To activate validation: define enum values on sort; set maximum on page and/or size.

^{Written for commit 67884e8. Summary will update on new commits.}