[Swift4] ParseError, "Date string does not match format expected by formatter." when date string has not miliseconds

Description

When CodableHelper decode a model with date, if that Date String hasn't milisecond (ex. "2019-02-14T00:00:00") the decoder throws a decode error.

Swagger-codegen version

tag -> 2.4.1 and later

Swagger declaration file content or url

  ModelV2:
    type: object
    properties:
      Name:
        type: string
      Url:
        type: string
      Description:
        type: string
      StartDate:
        format: date-time
        type: string
      EndDate:
        format: date-time
        type: string
      Type:
        enum:
          - XXXXType
          - XXXXType2
        type: string
      Size:
        type: string
      Order:
        format: int32
        type: integer

Steps to reproduce

Parse this model throws decode error:

{
   "Name": "XXXXXXX",
   "Url": "https://XXXXXX",
   "Description": "XXXXXDescription",
   "StartDate": "2019-02-14T00:00:00",
   "EndDate": "2019-02-28T00:00:00",
   "Type": "XXXXType",
   "Size": "375x255",
   "Order": 1
}

Suggest a fix/enhancement

I propouse this fix on CodableHelper.swift

Actual Code

    open class func decode<T>(_ type: T.Type, from data: Data) -> (decodableObj: T?, error: Error?) where T : Decodable {
        var returnedDecodable: T? = nil
        var returnedError: Error? = nil

        let decoder = JSONDecoder()
        if let df = self.dateformatter {
            decoder.dateDecodingStrategy = .formatted(df)
        } else {
            decoder.dataDecodingStrategy = .base64
            let formatter = DateFormatter()
            formatter.calendar = Calendar(identifier: .iso8601)
            formatter.locale = Locale(identifier: "en_US_POSIX")
            formatter.timeZone = TimeZone(secondsFromGMT: 0)
            formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSXXXXX"
            decoder.dateDecodingStrategy = .formatted(formatter)
        }

        do {
            returnedDecodable = try decoder.decode(type, from: data)
        } catch {
            returnedError = error
        }

        return (returnedDecodable, returnedError)
    }

New fix Code

    open class func decode<T>(_ type: T.Type, from data: Data) -> (decodableObj: T?, error: Error?) where T : Decodable {
        var returnedDecodable: T? = nil
        var returnedError: Error? = nil

        let decoder = JSONDecoder()
        if let df = self.dateformatter {
            decoder.dateDecodingStrategy = .formatted(df)
        } else {
            decoder.dataDecodingStrategy = .base64
            decoder.dateDecodingStrategy = .custom({ (decoder) -> Date in
                let container = try decoder.singleValueContainer()
                let dateStr = try container.decode(String.self)
                
                let formatter = DateFormatter()
                formatter.calendar = Calendar(identifier: .iso8601)
                formatter.locale = Locale(identifier: "en_US_POSIX")
                formatter.timeZone = TimeZone(secondsFromGMT: 0)
                
                formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSXXXXX"
                if let date = formatter.date(from: dateStr) {
                    return date
                }
                
                formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS"
                if let date = formatter.date(from: dateStr) {
                    return date
                }
                
                formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssXXXXX"
                if let date = formatter.date(from: dateStr) {
                    return date
                }
                
                formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss"
                if let date = formatter.date(from: dateStr) {
                    return date
                }
                
                throw DateError.invalidDate
            })
        }

        do {
            returnedDecodable = try decoder.decode(type, from: data)
        } catch {
            returnedError = error
        }

        return (returnedDecodable, returnedError)
    }

Start in CodableHelper.swift and reproduce the failure with the supplied ModelV2 JSON, comparing date strings with and without milliseconds. Done means the decoder accepts the shown date-time values without a decode error while preserving the existing custom date formatter behavior.