[BUG] [Rust] Cannot invoke "String.replaceAll(String, String)" because "name" is null

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Exception in thread "main" java.lang.RuntimeException: Could not process model 'custom_fields_attributes'.Please make sure that your schema is correct!
	at org.openapitools.codegen.DefaultGenerator.generateModels(DefaultGenerator.java:519)
	at org.openapitools.codegen.DefaultGenerator.generateModels(DefaultGenerator.java:444)
	at org.openapitools.codegen.DefaultGenerator.generate(DefaultGenerator.java:1292)
	at org.openapitools.codegen.cmd.Generate.execute(Generate.java:535)
	at org.openapitools.codegen.cmd.OpenApiGeneratorCommand.run(OpenApiGeneratorCommand.java:32)
	at org.openapitools.codegen.OpenAPIGenerator.main(OpenAPIGenerator.java:66)
Caused by: java.lang.NullPointerException: Cannot invoke "String.replaceAll(String, String)" because "name" is null
	at org.openapitools.codegen.languages.AbstractRustCodegen.sanitizeIdentifier(AbstractRustCodegen.java:187)
	at org.openapitools.codegen.languages.AbstractRustCodegen.toModelName(AbstractRustCodegen.java:353)
	at org.openapitools.codegen.languages.RustClientCodegen.fromModel(RustClientCodegen.java:307)
	at org.openapitools.codegen.DefaultGenerator.processModels(DefaultGenerator.java:1754)
	at org.openapitools.codegen.DefaultGenerator.generateModels(DefaultGenerator.java:514)
	... 5 more

openapi-generator version

Tried 7.16.0 and latest master branch.

OpenAPI declaration file content or url

openapi: 3.1.0
info:
  title: Example
  version: 1.0.0
paths:
  "/example":
    patch:
      requestBody:
        required: true
        content:
          application/json:
            schema:
              contact:
                type: object
                properties:
                  custom_fields_attributes:
                    $ref: "#/components/schemas/custom_fields_attributes"
      responses:
        "200":
          description: "Success"
          content:
            application/json:
              schema:
                type: object
components:
  schemas:
    custom_fields_attributes:
      oneOf:
        - type: object
          additionalProperties:
            type: object
            properties:
              id:
                type:
                  - integer
                  - string
              value:
                type: string
            required:
              - id
              - value
        - type: array
          items:
            type: object
            properties:
              id:
                type:
                  - integer
                  - string
              value:
                type: string

Generation Details

openapi-generator-cli generate -i example.yaml -o /tmp/example -g rust --package-name example

Steps to reproduce

openapi-generator-cli generate -i example.yaml -o /tmp/example -g rust --package-name example

Related issues/PRs

• https://github.com/OpenAPITools/openapi-generator/issues/21192

Start with org.openapitools.codegen.languages.AbstractRustCodegen.sanitizeIdentifier and toModelName, then inspect RustClientCodegen.fromModel and reproduce with the supplied OpenAPI YAML and rust generation command. Done means generation no longer fails with the reported null-pointer exception and the regression is covered by an appropriate generator test.