fix: OpenAPI schema missing minItems/maxItems for msgspec Meta on collections

[worksbyfriday]

Summary

Fixes #4514.

When using Annotated[list[T], Meta(min_length=N)] on a msgspec Struct field, the OpenAPI schema generation did not include minItems/maxItems, even though:

• Runtime validation worked correctly (msgspec rejects short arrays)
• msgspec.json.schema() correctly generated minItems

The constraint metadata was lost at two boundaries:

1. litestar/plugins/core/_msgspec.py: kwarg_definition_from_field() extracted min_length/max_length for string/bytes types (lines 65-77) but not for collection types (ListType, SetType, FrozenSetType, VarTupleType). Added collection type handling that maps min_length → min_items and max_length → max_items.

2. litestar/typing.py: _annotated_types_extractor() handled annotated_types.MinLen/MaxLen but not msgspec.Meta (which is a separate class, not an annotated_types subclass). Added a branch for msgspec.Meta that extracts all constraint attributes, correctly mapping length constraints to items constraints for sequence containers.

Before

"category_ids": {
  "items": {"type": "string", "format": "uuid"},
  "type": "array"
}

After

"category_ids": {
  "items": {"type": "string", "format": "uuid"},
  "type": "array",
  "minItems": 1
}

Test plan

• Added test_create_schema_from_msgspec_annotated_collection_type verifying minItems/maxItems for list and set fields
• Verified reporter's exact reproduction case produces correct schema
• Verified existing test_create_schema_from_msgspec_annotated_type still passes (no regression on int/str/bytes fields)

[provinzkraut]

This should not be handled here, since it's an implementation specific thing. It should be handled in the plugin. You can check how it's handled for other msgspec constraints / Pydantic, within their respective plugins.

[worksbyfriday]

You're right. Removed the msgspec.Meta handling from _annotated_types_extractor. The plugin's kwarg_definition_from_field now handles collection types — msgspec.inspect already unwraps Meta into ListType(min_length=...), so the plugin just needs to extract those fields.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.85%. Comparing base (3dc3507) to head (019184b).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4605   +/-   ##
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  Coverage   97.85%   97.85%           
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  Files         297      297           
  Lines       15344    15347    +3     
  Branches     1722     1723    +1     
=======================================
+ Hits        15015    15018    +3     
  Misses        188      188           
  Partials      141      141           

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[worksbyfriday]

Both review items addressed:

1. Moved msgspec.Meta handling to the plugin (commit bde4c46)
2. Merged the collection test into the existing test case (commit 777b4f6)

Ready for another look.

[github-actions]

Documentation preview will be available shortly at https://litestar-org.github.io/litestar-docs-preview/4605