feat: add contains/minContains/maxContains members

[Poltuu]

Pull Request

Description

Adds the JSON Schema 2020-12 array keywords contains, maxContains, and minContains to the Schema Object, as required by the OpenAPI 3.1/3.2 specifications.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Related Issue(s)

Closes #2875 #2875

Changes Made

• Added Contains (IOpenApiSchema?), MaxContains (int?), and MinContains (int?) members to IOpenApiSchema, OpenApiSchema, and OpenApiSchemaReference, plus contains/maxContains/minContains constants in OpenApiConstants.
• Added deserialization in the V3.1 and V3.2 schema readers and serialization in WriteJsonSchemaKeywords (emitted for OpenAPI 3.1+ only; dropped on 3.0/2.0 downcast, consistent with dependentRequired).
• Updated PublicAPI.Unshipped.txt with the new public surface.

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• All existing tests pass

Checklist

• My code follows the code style of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Versions applicability

• My change applies to the version 1.X of the library, if so PR link:
• My change applies to the version 2.X of the library, if so PR link:
• My change applies to the version 3.X of the library, if so PR link: this PR
• I have evaluated the applicability of my change against the other versions above.

See the contributing guidelines for more information about how patches are applied across multiple versions.

Additional Notes

[baywet]

Thanks for the contribution!
Left a couple of comments to help get this merged.
Also realized that a couple of other properties were missing:

• #2877
• #2878
• #2879

[baywet]

Thank you for making the changes!

Added a couple more comments

[github-code-quality]

Code Coverage Overview

Languages: C#

C# / code-coverage/dotnet

The overall coverage in the main branch remains at 88%, unchanged from the main branch.

Show a code coverage summary of the most impacted files.

File	main 21488c6	main b635242	+/-
/home/runner/wo...penApiWalker.cs	80%	80%	0%
/home/runner/wo...emaReference.cs	93%	93%	0%
/home/runner/wo...penApiSchema.cs	99%	99%	0%
/home/runner/wo...ApiWorkspace.cs	89%	89%	0%
/home/runner/wo...Deserializer.cs	87%	90%	+3%
/home/runner/wo...Deserializer.cs	87%	90%	+3%
/home/runner/wo...Deserializer.cs	81%	86%	+5%

---

_{Updated June 09, 2026 18:40 UTC
Code Coverage is in Public Preview. Learn more and provide us with your feedback.}