$ref not fully resolved for object with no type

[phiz71]

Hi, I want to parse an openAPI document with $ref but even with the resolveFully option, it does not work.

Problem

I want to parse this document

openapi: 3.0.0
info:
  title: no type resolution
  version: 1.0.0
paths:
  /foo:
    post:
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/FooInput'
      responses:
        '200':
          description: subscription successfully created
components:
  schemas:
    FooInput:
      properties:
        bar:
          type: string
        input:
          $ref: '#/components/schemas/BazInput'
    BazInput:
      properties:
        baz:
          type: string

I use the resolveFully option and I expect to have this result:

openapi: 3.0.0
info:
  title: no type resolution
  version: 1.0.0
servers:
- url: /
paths:
  /foo:
    post:
      requestBody:
        content:
          application/json:
            schema:
              properties:
                bar:
                  type: string
                input:
                  properties:
                    baz:
                      type: string
        required: true
      responses:
        "200":
          description: subscription successfully created
components:
  schemas:
    FooInput:
      properties:
        bar:
          type: string
        input:
          properties:
            baz:
              type: string
    BazInput:
      type: object
      properties:
        baz:
          type: string

But instead, the FooInput.input ref is not resolved.

openapi: 3.0.0
info:
  title: no type resolution
  version: 1.0.0
servers:
- url: /
paths:
  /foo:
    post:
      requestBody:
        content:
          application/json:
            schema:
              properties:
                bar:
                  type: string
                input:
                  $ref: '#/components/schemas/BazInput'
        required: true
      responses:
        "200":
          description: subscription successfully created
components:
  schemas:
    FooInput:
      properties:
        bar:
          type: string
        input:
          $ref: '#/components/schemas/BazInput'
    BazInput:
      properties:
        baz:
          type: string

Analysis

After some test, i found out that if I add type: object to either FooInput schema or BazInput schema, the resolution is correct.

If i add type: object in FooInput, the resolver execute this code (io.swagger.v3.parser.util.ResolverFully):
https://github.com/swagger-api/swagger-parser/blob/master/modules/swagger-parser-v3/src/main/java/io/swagger/v3/parser/util/ResolverFully.java#L323

if (schema instanceof ObjectSchema) {
  ObjectSchema obj = (ObjectSchema) schema;
  if(obj.getProperties() != null) {
    Map<String, Schema> updated = new LinkedHashMap<>();
    for(String propertyName : obj.getProperties().keySet()) {
      Schema innerProperty = obj.getProperties().get(propertyName);
      // reference check
      if(schema != innerProperty) {
        updated.put(propertyName, resolveSchemaProperty(propertyName, innerProperty));
      }
    }
    obj.setProperties(updated);
  }
  return obj;
}

If i add type: object in BazInput, the resolver execute this code (io.swagger.v3.parser.util.ResolverFully):
https://github.com/swagger-api/swagger-parser/blob/master/modules/swagger-parser-v3/src/main/java/io/swagger/v3/parser/util/ResolverFully.java#L398

if(property instanceof ObjectSchema) {
  ObjectSchema op = (ObjectSchema) property;
  if (op.getProperties() != model.getProperties()) {
    if (property.getType() == null) {
      property.setType("object");
    }
    model.addProperties(key, property);
  } else {
    LOGGER.debug("not adding recursive properties, using generic object");
    ObjectSchema newSchema = new ObjectSchema();
    model.addProperties(key, newSchema);
  }
}

Proposition

I think there is a problem in the second part of code.

    if (property.getType() == null) {
      property.setType("object");
    }

Because if property is an instance of ObjectSchema, it means property.getType() is not null.
So I propose to remove the if and to keep only:

//if(property instanceof ObjectSchema) {
//  ObjectSchema op = (ObjectSchema) property;
  if (property.getProperties() != model.getProperties()) {
    if (property.getType() == null) {
      property.setType("object");
    }
    model.addProperties(key, property);
  } else {
    LOGGER.debug("not adding recursive properties, using generic object");
    ObjectSchema newSchema = new ObjectSchema();
    model.addProperties(key, newSchema);
  }
//}

If you are ok with this, I can create a PR.

[gracekarina]

hey @phiz71, please create the PR and we will test the impact in other OSS projects dependant of parser, and see if anything breaks 😉
Thanks!