[BUG][rust-server] serde_valid validation stops at generated model wrappers #25261

Bug Report Checklist

• Minimal spec provided and validated with the CLI.
• Reproduced on latest master (1fdc3307942fcf853990cda8701d71c7e0753157).
• Searched open and closed issues and PRs.
• Actual and expected output provided below.

Description

With the Rust server generator's validate feature, a root model's serde_valid::Validate call can return success when a nested model is invalid. Generated array newtypes derive Validate, but their inner fields do not have #[validate]. Named oneOf/anyOf newtypes have the same missing recursion step. Object fields also omit nested validation when they have length or item bounds.

This makes a root validation call unreliable as a structural validation boundary. Applications must walk generated model graphs by hand to find invalid children.

OpenAPI Generator version

Latest master, built locally at 1fdc3307942fcf853990cda8701d71c7e0753157. The array-wrapper case also applies to 7.22.0 and 7.26.0.

Minimal OpenAPI definition

openapi: 3.0.3
info:
  title: Nested validation
  version: '1.0'
paths: {}
components:
  schemas:
    Positive:
      type: object
      required: [value]
      properties:
        value:
          type: integer
          minimum: 1
    Positives:
      type: array
      items:
        $ref: '#/components/schemas/Positive'
    Parent:
      type: object
      required: [children]
      properties:
        children:
          $ref: '#/components/schemas/Positives'

Generation and reproduction

Generate with:

java -jar openapi-generator-cli.jar generate \
  -g rust-server -i nested.yaml --generate-alias-as-model \
  --additional-properties packageName=recursive_validation -o generated

Add this integration test and run cargo test --no-default-features --features validate --test recursive_validation:

use recursive_validation::models::{Parent, Positive, Positives};
use serde_valid::Validate;

#[test]
fn root_validation_reaches_array_items() {
    let root = Parent {
        children: Positives::from(vec![Positive { value: 0 }]),
    };
    assert!(root.validate().is_err());
}

Actual: the assertion fails because validation returns Ok(()). Expected: the root reports the child's minimum violation.

Proposed fix

Generate recursion through model-valued wrapper fields and keep recursive validation when a field also has collection bounds. Primitive-valued wrappers and primitive union alternatives must still compile; Rust primitives such as String do not implement serde_valid::Validate.