Non-nullable properties are marked as optional in generated TypeScript

I have the YAML below. Two properties are explicit nullable: true (completedBy, completedTime) while the others are implicit nullable: false. When generating a TypeScript client I get the following interface:

export interface ITask {
    plantId?: string;
    hoursInterval?: number;
    deadline?: Date;
    completedBy?: string | null;
    completedTime?: Date | null;
    taskId?: string;
}

I would expect all properties to not have the ? as they are not nullable. Except of course completedBy and completedTime.

openapi: 3.0.1
info:
  title: Non-nullable demo
  description: Non-nullable properties are treated as nullable in generated TypeScript
  version: v1
servers:
  - url: /v1
    description: Api version 1.0
paths:
  '/tasks':
    get:
      summary: ''
      tags: []
      operationId: getTasks
      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Tasks'
components:
  schemas:
    Tasks:
      description: A list of tasks.
      type: array
      items:
        $ref: '#/components/schemas/Task'
      x-tags:
        - Tasks
      title: Tasks
    Task:
      title: Task
      type: object
      description: A task.
      properties:
        plantId:
          type: string
        hoursInterval:
          type: integer
        deadline:
          type: string
          format: date-time
        completedBy:
          nullable: true
          type: string
        completedTime:
          nullable: true
          type: string
          format: date-time
        taskId:
          type: string

[kev-andrews]

Thank you for great suggestion!

@Liwoj Our schema processor looks like this:

public class MarkAsRequiredIfNonNullableSchemaProcessor : ISchemaProcessor
{
    public void Process(SchemaProcessorContext context)
    {
        foreach (var (propName, prop) in context.Schema.Properties)
        {
            if (!prop.IsNullable(SchemaType.OpenApi3))
            {
                prop.IsRequired = true;
            }
        }
    }
}

And registering it looks like this:

options.SchemaProcessors.Add(new MarkAsRequiredIfNonNullableSchemaProcessor());

I agree that the default behaviour seems strange here.

If anyone has problems with the current workaround not functioning correctly for schemas involving inheritance, this seems to be fixed by looping over Schema.ActualProperties instead of Schema.Properties

[jgilchrist]

@Liwoj Our schema processor looks like this:

public class MarkAsRequiredIfNonNullableSchemaProcessor : ISchemaProcessor
{
    public void Process(SchemaProcessorContext context)
    {
        foreach (var (propName, prop) in context.Schema.Properties)
        {
            if (!prop.IsNullable(SchemaType.OpenApi3))
            {
                prop.IsRequired = true;
            }
        }
    }
}

And registering it looks like this:

options.SchemaProcessors.Add(new MarkAsRequiredIfNonNullableSchemaProcessor());

I agree that the default behaviour seems strange here.