[BUG] 'oneOf' attribute not working for schema properties

Description

Exception in thread "main" java.lang.RuntimeException: Could not generate model 'Pet_address'
at org.openapitools.codegen.DefaultGenerator.generateModels(DefaultGenerator.java:554)
at org.openapitools.codegen.DefaultGenerator.generate(DefaultGenerator.java:911)
at org.openapitools.codegen.cmd.Generate.execute(Generate.java:465)
at org.openapitools.codegen.cmd.OpenApiGeneratorCommand.run(OpenApiGeneratorCommand.java:32)
at org.openapitools.codegen.OpenAPIGenerator.main(OpenAPIGenerator.java:66)
Caused by: java.lang.StringIndexOutOfBoundsException: String index out of range: 1
at java.lang.String.substring(String.java:1963)
at org.openapitools.codegen.templating.mustache.TitlecaseLambda.titleCase(TitlecaseLambda.java:64)
at org.openapitools.codegen.templating.mustache.TitlecaseLambda.execute(TitlecaseLambda.java:80)
at com.samskivert.mustache.Mustache$SectionSegment.execute(Mustache.java:874)
at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
at com.samskivert.mustache.Mustache$SectionSegment.execute(Mustache.java:870)
at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
at com.samskivert.mustache.Mustache$InvertedSegment.execute(Mustache.java:910)
at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
at com.samskivert.mustache.Mustache$SectionSegment.execute(Mustache.java:866)
at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
at com.samskivert.mustache.Mustache$SectionSegment.execute(Mustache.java:881)
at com.samskivert.mustache.Template.executeSegs(Template.java:157)
at com.samskivert.mustache.Mustache$IncludedTemplateSegment.execute(Mustache.java:774)
at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
at com.samskivert.mustache.Mustache$SectionSegment.execute(Mustache.java:870)
at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
at com.samskivert.mustache.Mustache$SectionSegment.execute(Mustache.java:866)
at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
at com.samskivert.mustache.Mustache$InvertedSegment.execute(Mustache.java:910)
at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
at com.samskivert.mustache.Mustache$SectionSegment.execute(Mustache.java:881)
at com.samskivert.mustache.Mustache$BlockSegment.executeSegs(Mustache.java:845)
at com.samskivert.mustache.Mustache$SectionSegment.execute(Mustache.java:866)
at com.samskivert.mustache.Template.executeSegs(Template.java:157)
at com.samskivert.mustache.Template.execute(Template.java:134)
at com.samskivert.mustache.Template.execute(Template.java:125)
at org.openapitools.codegen.templating.MustacheEngineAdapter.compileTemplate(MustacheEngineAdapter.java:65)
at org.openapitools.codegen.TemplateManager.write(TemplateManager.java:163)
at org.openapitools.codegen.DefaultGenerator.processTemplateToFile(DefaultGenerator.java:1057)
at org.openapitools.codegen.DefaultGenerator.processTemplateToFile(DefaultGenerator.java:1044)
at org.openapitools.codegen.DefaultGenerator.generateModel(DefaultGenerator.java:393)
at org.openapitools.codegen.DefaultGenerator.generateModels(DefaultGenerator.java:545)
... 4 more

openapi-generator version : 6.0.1

OpenAPI declaration file content or url

openapi: 3.0.3
info:
title: One Of Array Troubleshooting
version: 0.0.0
servers:

• url: https://petstore3.swagger.io/api/v3
  paths:
  /pet:
  put:
  tags:
  - pet
  requestBody:
  content:
  application/json:
  schema:
  $ref: '#/components/schemas/Pet'
  application/xml:
  schema:
  $ref: '#/components/schemas/Pet'
  application/x-www-form-urlencoded:
  schema:
  $ref: '#/components/schemas/Pet'
  required: true
  responses:
  '200':
  description: Successful operation
  content:
  application/json:
  schema:
  $ref: '#/components/schemas/Pet'
  application/xml:
  schema:
  $ref: '#/components/schemas/Pet'
  '400':
  description: Invalid ID supplied
  '404':
  description: Pet not found
  '405':
  description: Validation exception
  components:
  schemas:
  Pet:
  type: object
  properties:
  id:
  type: integer
  format: int64
  example: 10
  name:
  type: string
  example: doggie
  address:
  oneOf:
  - type: array
  items:
  $ref: '#/components/schemas/Address'
  minItems: 1
  xml:
  name: pet
  Address:
  type: object
  properties:
  id:
  type: integer
  format: int64
  example: 10

Generation Details

Steps to reproduce

Related issues/PRs

Suggest a fix

Reproduce the failure with the supplied OpenAPI 3.0.3 declaration using openapi-generator 6.0.1, then inspect TitlecaseLambda.titleCase in org.openapitools.codegen.templating.mustache.TitlecaseLambda.java at the reported stack-trace line. Follow the generation path through DefaultGenerator.generateModels and OpenAPIGenerator; done means the Pet_address model generation completes without the StringIndexOutOfBoundsException.