Duplicate types in nested schemas

[drewcorlin1]

Given a JsonSchema with nested type with a oneOf where the eligible sub-types map to the same typescript type, the resulting typescript type has a duplicate type (eg string | string).

For example

import { compile } from 'json-schema-to-typescript';

compile(
  {
    type: 'object',
    properties: {
      items: {
        type: 'array',
        items: {
          type: 'object',
          properties: {
            myField: { oneOf: [{ type: 'string' }, { type: 'string' }] },
          },
        },
      },
    },
  },
  'MyType',
).then(console.log);

produces

export interface Drew {
  items?: {
    myField?: string | string; // Would have expected just string here
    [k: string]: unknown;
  }[];
  [k: string]: unknown;
}

Interestingly the same does not happen when the oneOf type is at the top level of the JsonSchema

import { compile } from 'json-schema-to-typescript';

compile(
  {
    type: 'object',
    properties: {
      myField: {
        oneOf: [{ type: 'string' }, { type: 'string' }],
      },
    },
  },
  'MyType',
).then(console.log);

produces

export interface MyType {
  myField?: string;
  [k: string]: unknown;
}

In reality my schema uses different formats though they map to the same type, so I simplified the examples above

{
    type: 'object',
    properties: {
      myField: {
        oneOf: [
          { type: 'string', format: 'uuid', },
          { type: 'string', pattern: '^[23456789ABCDEFGHJKMNPQRSTUVWXYZ]{12}$', },
        ],
      },
    },
  }