[BUG] ModelBase.cpp fromJson method for int64 types always returns 0, regardless of JSON value

Created by: shimmerLum

Bug Report Checklist

Have you provided a full/minimal spec to reproduce the issue?
Have you validated the input using an OpenAPI validator (example)?
Have you tested with the latest master to confirm the issue still exists?
Have you searched for related issues/PRs?
What's the actual output vs expected output?

Description

Hello! I am attempting to determine if I have found a bug in the openapi-generator for cpprestsdk or if there's just a bug in my project (i.e. JSON or API spec).

I used the openapi-generator to generate cpprest code from a JSON definition given as input. The JSON definition is linked below. My definition uses int64 numbers and the generated bool ModelBase::fromJson( const web::json::value& val, int64_t & outVal ) implementation in ModelBase.cpp always returns 0, regardless of the JSON value.

openapi-generator version

I have used openapi-generator-cli-5.0.0-beta3.jar when I found the bug, but I tested with the latest from master, as well, using the following:

The bug can still be reproduced with the list of generators above.

OpenAPI declaration file content or url

The test.json file used as input to the openapi-generator

Generation Details

This is the code generated for the bool ModelBase::fromJson( const web::json::value& val, int64_t & outVal ) method, from ModelBase.cpp:

bool ModelBase::fromJson( const web::json::value& val, int64_t & outVal )
{
    outVal = !val.is_null() ? std::numeric_limits<int64_t>::quiet_NaN() : val.as_number().to_int64();
    return val.is_number();
}

The line that generates the bug seems to be outVal = !val.is_null() ? std::numeric_limits<int64_t>::quiet_NaN() : val.as_number().to_int64(); specifically the condition by which the value is assigned: !val.is_null().

This number will never be null, therefore the condition will always be true and the assigned value std::numeric_limits<int64_t>::quiet_NaN() (which, in my case, is 0).

Steps to reproduce

You need to have cpprestsdk and Java installed on your machine.

Copy the test.json definition.
Run the openapi-generator as follows:

java -jar openapi-generator-cli-5.0.1-20210114.161254-35.jar generate -i test.json -g cpprest-sdk -o output_folder

Go to output_folder and open ModelBase.cpp. Line 278 contains the bug.

Suggest a fix

Looking through similar code generated for other data types(such as int32, float, double), I think the condition should be !val.is_number(), because 'number' is the data type that is being used to convert from to int64:

outVal = !val.is_number() ? std::numeric_limits<int64_t>::quiet_NaN() : val.as_number().to_int64();

Thank you!