[BUG] aspnetcore generator optional string query param dataType `string` instead of `string?`

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• 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

The dataType of the function signature should be string? and not string for the uuid parameter.
Note that the offset parameter (integer) is generated properly with the ?.

Actual output:

public abstract IActionResult ApisV1ProjectsProjectIdWorkUnitDataGet([FromRoute (Name = "projectId")][Required]int projectId, [FromQuery (Name = "offset")]int? offset, [FromQuery (Name = "uuid")][RegularExpression("^([0-9A-Fa-f]{8}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{12})$")]string uuid);

Expected output:

public abstract IActionResult ApisV1ProjectsProjectIdWorkUnitDataGet([FromRoute (Name = "projectId")][Required]int projectId, [FromQuery (Name = "offset")]int? offset, [FromQuery (Name = "uuid")][RegularExpression("^([0-9A-Fa-f]{8}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{12})$")]string? uuid);

openapi-generator version

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  title: API
  version: 0.0.0
servers:
  - url: /_apis/v1/
security:
  - basicAuth: []
tags:
  - description: Work-unit data
    name: work-unit data
paths:
  /projects/{projectId}/workUnitData:
    get:
      summary: Get work-unit data
      tags:
        - work-unit data
      operationId: _apis.v1.projects.projectId.workUnitData.get
      parameters:
        - $ref: '#/components/parameters/projectId'
        - $ref: '#/components/parameters/offset'
        - $ref: '#/components/parameters/uuid'
      responses:
        '200':
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/WorkUnitData'
          description: Confirmation of project registration
        '500':
          description: Internal server error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
        '404':
          description: '`projectId` not found.'
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'

 
components:
  parameters:
    uuid:
      description: UUID of working list
      in: query
      explode: true
      name: uuid
      required: false
      schema:
        pattern: "^([0-9A-Fa-f]{8}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{4}[-][0-9A-Fa-f]{12})$"
        type: string
      style: form
    offset:
      description: Offset for paging
      explode: true
      in: query
      name: offset
      required: false
      schema:
        minimum: 0
        type: integer
      style: form
    limit:
      description: Limit for paging
      explode: true
      in: query
      name: limit
      required: false
      schema:
        minimum: 0
        type: integer
      style: form
    workUnitDatumId:
      description: Work-unit datum identifier
      in: path
      name: workUnitDatumId
      required: true
      schema:
        minimum: 1
        type: integer
    projectId:
      description: Project identifier
      in: path
      name: projectId
      required: true
      schema:
        minimum: 1
        type: integer
  schemas:
    WorkUnitData:
      additionalProperties: false
      example:
        total: 100
        count: 1
        items:
          - workUnitDatumId: 1
            workUnitId: 1
            sentence: I love my teacher
            comment: I love my teacher. I also love my TA.
            jobTypeName: eec
            jobTypeVersion: 0.0.0
          - workUnitDatumId: 2
            workUnitId: 1
            sentence: I love my teacher
            comment: I love my teacher. I also love my TA.
            jobTypeName: eec
            jobTypeVersion: 0.0.0
      properties:
        count:
          description: Number of records in the current page
          example: 1
          minimum: 0
          readOnly: true
          type: integer
        total:
          description: Total number of records accross all pages
          example: 100
          minimum: 0
          readOnly: true
          type: integer
        items:
          items:
            $ref: '#/components/schemas/WorkUnitDatum'
          readOnly: true
          type: array
        _links:
          $ref: '#/components/schemas/PageLinks'
      required:
        - count
        - items
        - total
        - _links
      type: object
    WorkUnitDatum:
      additionalProperties: false
      example:
        workUnitDatumId: 1
        workUnitId: 1
        sentence: I love my teacher
        comment: I love my teacher. I also love my TA.
        jobTypeName: eec
        jobTypeVersion: 0.0.0
      properties:
        workUnitDatumId:
          description: Identifier of the work-unit datum
          readOnly: true
          type: integer
          minimum: 1
        workUnitId:
          description: Identifier of the work-unit
          readOnly: true
          type: integer
          minimum: 1
        sentence:
          description: Sentence of a comment
          readOnly: true
          type: string
        comment:
          description: Comment
          readOnly: true
          type: string
        jobTypeName:
          description: Jobtype name associated to work-unit
          readOnly: true
          type: string
        jobTypeVersion:
          description: Jobtype version associated to work-unit
          readOnly: true
          type: string
          pattern: ^[0-9]+\.[0-9]+\.[0-9]+$
      required:
        - workUnitDatumId
        - workUnitId
        - comment
        - projectId
      type: object
      
    PageLinks:
      type: object
      properties:
        self:
          type: string
          readOnly: true
          description: Opaque link to the current page
        prev:
          type: string
          readOnly: true
          description: Opaque link to the previous page
        next:
          type: string
          readOnly: true
          description: Opaque link to the next page
      additionalProperties: false
      required:
        - self

    Error:
      additionalProperties: false
      properties:
        type:
          description: A URI reference that identifies the problem type.
          readOnly: true
          type: string
        title:
          description: 'A short, human-readable summary of the problem type.'
          readOnly: true
          type: string
        status:
          description: The HTTP status code.
          readOnly: true
          type: integer
        detail:
          description: A human-readable explanation specific to this occurrence of the problem.
          readOnly: true
          type: string
        instance:
          description: A URI reference that identifies the specific occurrence of the problem.
          readOnly: true
          type: string
        timestamp:
          description: Timestamp of the error.
          format: date-time
          readOnly: true
          type: string
      required:
        - status
        - timestamp
        - title
        - type
      type: object
      
  securitySchemes:
    basicAuth:
      scheme: basic
      type: http

Generation Details

openapi-generator-cli 5.1.1-SNAPSHOT

docker run --rm -v "${PWD}:/local" openapitools/openapi-generator-cli generate -i local/openapi/openapi.yaml -g aspnetcore -o local/WorkflowApiOpenApi -p aspnetCoreVersion=5.0 -p packageVersion=0.0.0 -p isLibrary=true -p packageName=WorkflowApiOpenApi --config local/openapi/config.yaml -p operationModifier=abstract -p classModifier=abstract

Steps to reproduce

Generate with above command

Related issues/PRs

#9234

Suggest a fix

Good datatype.

Start by reproducing the issue with the supplied OpenAPI declaration and generation command, then inspect the aspnetcore generator's parameter type handling for the uuid and offset query parameters. Done means the generated signature uses string? for optional uuid while retaining int? for offset, with coverage for this case.