import io.swagger.parser.OpenAPIParser;
import io.swagger.v3.oas.models.OpenAPI;
import io.swagger.v3.oas.models.media.Schema;
import io.swagger.v3.parser.core.models.ParseOptions;
import io.swagger.v3.parser.core.models.SwaggerParseResult;

public class TestMissingNullableForSharedResponse {
    public static void main(String[] args) {
        String spec = """
            swagger: '2.0'
            info:
              version: 1.0.0
              title: Test
            responses:
              SharedResponse:
                description: Shared response
                schema:
                  type: object
                  properties:
                    optional_field:
                      type: integer
                      x-nullable: true
            paths:
              /endpoint1:
                get:
                  responses:
                    '200':
                      $ref: '#/responses/SharedResponse'
              /endpoint2:
                get:
                  responses:
                    '200':
                      $ref: '#/responses/SharedResponse'
            """;

        ParseOptions options = new ParseOptions();
        options.setResolve(true);
        options.setResolveFully(true);

        SwaggerParseResult result = new OpenAPIParser().readContents(spec, null, options);
        OpenAPI api = result.getOpenAPI();

        Schema endpoint_1 = getOptionalField(api, "/endpoint1");
        System.out.println("/endpoint1 nullable: " + endpoint_1.getNullable());

        Schema endpoint_2 = getOptionalField(api, "/endpoint2");
        System.out.println("/endpoint2 nullable: " + endpoint_2.getNullable());
    }

    private static Schema getOptionalField(OpenAPI api, String path) {
        return (Schema) api.getPaths().get(path)
                .getGet()
                .getResponses().get("200")
                .getContent().values().iterator().next()
                .getSchema()
                .getProperties().get("optional_field");
    }
}