Swagger plugin type Date throws circular dependency error

I’m submitting a…

[ ] Regression 
[X] Bug report
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead post your question on Stack Overflow.

Current behavior

The new Swagger plugin https://docs.nestjs.com/recipes/swagger does not correctly work with type Date. It returns the following error:

(node:2603) UnhandledPromiseRejectionWarning: Error: A circular dependency has been detected (property key: "createdOn"). Please, make sure that each side of a bidirectional relationships are using lazy resolvers ("type: () => ClassType").
    at SchemaObjectFactory.createNotBuiltInTypeReference (/Users/skgu/Projects/NestCliTest/wtf/node_modules/@nestjs/swagger/dist/services/schema-object-factory.js:107:19)
    at SchemaObjectFactory.mergePropertyWithMetadata (/Users/skgu/Projects/NestCliTest/wtf/node_modules/@nestjs/swagger/dist/services/schema-object-factory.js:88:25)
    at /Users/skgu/Projects/NestCliTest/wtf/node_modules/@nestjs/swagger/dist/services/schema-object-factory.js:55:35
    at Array.map (<anonymous>)
    at SchemaObjectFactory.exploreModelSchema (/Users/skgu/Projects/NestCliTest/wtf/node_modules/@nestjs/swagger/dist/services/schema-object-factory.js:54:52)
    at ResponseObjectFactory.create (/Users/skgu/Projects/NestCliTest/wtf/node_modules/@nestjs/swagger/dist/services/response-object-factory.js:45:47)
    at /Users/skgu/Projects/NestCliTest/wtf/node_modules/@nestjs/swagger/dist/explorers/api-response.explorer.js:50:96
    at /Users/skgu/Projects/NestCliTest/wtf/node_modules/lodash/lodash.js:13401:38
    at /Users/skgu/Projects/NestCliTest/wtf/node_modules/lodash/lodash.js:4905:15
    at baseForOwn (/Users/skgu/Projects/NestCliTest/wtf/node_modules/lodash/lodash.js:2990:24)
(node:2603) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:2603) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Using ApiProperty still gives the error. If I put @IsDate() then the error disappears. Without the Date the schema is generated correctly.

Expected behavior

it should not give a circular dependency error.

Minimal reproduction of the problem with instructions

Create CLI project and add swagger plugin in compile options:

{
  "collection": "@nestjs/schematics",
  "sourceRoot": "src",
  "compilerOptions": {
    "plugins": [
      {
        "name": "@nestjs/swagger/plugin",
        "options": {
          "classValidatorShim": false
        }
      }
    ]
  }
}

Next create a DTO with a property of type Date:

export class HelloDto {
  public createdOn: Date;
}

Run app

npm start

this should result in an error.

What is the motivation / use case for changing the behavior?

Environment

```
  "dependencies": {
    "@nestjs/common": "^6.7.2",
    "@nestjs/core": "^6.7.2",
    "@nestjs/platform-express": "^6.7.2",
    "@nestjs/swagger": "4.1.2",
    "reflect-metadata": "^0.1.13",
    "rimraf": "^3.0.0",
    "rxjs": "^6.5.3",
    "swagger-ui-express": "^4.1.2"
  },
```

Others:

[anotherpit]

Seems like it got broken in this commit: https://github.com/nestjs/swagger/commit/321ff913083c66f3d385d5ed3c4933201ad97b7e

Specifically, on this line there should be

...existingMetadata

not

existingMetadata

Downgrade to version 4.0.9 (not ~4.0.9, but exactly 4.0.9) fixed the issue for me

[kamilmysliwiec]

Problem described in this issue seems to be resolved:

@treffynnon if you’re still seeing errors, please, create a separate issue with a repository that reproduces your problem.