[Question] [typescript-fetch] The date format (RFC 3339: full-date) has a time zone gap when parsing from JSON and when converting to JSON

[mdoi2]

target: typescript-fetch
openapi-generator version: 4.3.0

For example, if we generate from the definition of requestBody like this:

requestBody:
  required: true
  content:
    application/json:
      schema:
        title: RequestBody
        type: object
        properties:
          date:
            type: string
            format: date
            nullable: true

Such a code will be generated in the models directory:

export interface RequestBody {
  date?: Date | null;
}

export function RequestBodyFromJSON(json: any): RequestBody {
  return RequestBodyFromJSONTyped(json, false);
}

export function RequestBodyFromJSONTyped(json: any, ignoreDiscriminator: boolean): RequestBody {
  if ((json === undefined) || (json === null)) {
    return json;
  }
  return {
    'date': !exists(json, 'date') ? undefined : (json['date'] === null ? null : new Date(json['date'])),
  };
}

export function RequestBodyToJSON(value?: RequestBody | null): any {
  if (value === undefined) {
    return undefined;
  }
  if (value === null) {
    return null;
  }
  return {
    'date': value.date === undefined ? undefined : (value.date === null ? null : value.date.toISOString().substr(0,10)),
  };
}

Since the date format of OpenAPI conforms to RFC 3339 full-date, the time zone is not included in the original data string. ex: '2020-04-15'

When converting this original date string with the RequestBodyFromJSONTyped method, specify this string directly in the parameter of new Date, so it will be optimized in the local time zone.

I don't think this behavior is a problem.

But, when converting to JSON with the RequestBodyToJSON method, since it is converted to a string by toISOString, the UTC date is output.
With this, the value changes between conversion and restoration.

I think it should stringify with the date in the timezone of the Date instance.
For example:

`${value.date.getFullYear()}-${(value.date.getMonth() + 1).toString().padStart(2, '0')}-${value.date.getDate().toString().padStart(2, '0')}`

Is this my perception correct? Or am I doing something wrong?

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[LeComptoirDesPharmacies]

Hi @m-doi2,
Mhhh, I just had the same problem as yours.
I tried your proposal but padStart is a 'ES2017' feature which is not the default compiler option (for better compatibility).

Two other solutions are the following :
Require moment.js and use moment(date).format('YYYY-MM-DD').
Cons : It will ad dependency on generated client which could potentially increase size of projects using this codegen.

Write a "from scratch"method in runtime.js to convert Javascript "Date" type to ISO date string, maybe using this pattern : https://stackoverflow.com/a/25159403

Write a "hacky" method in runtime.js which will use toLocalDateString and transform to align with ISO format :

export function toDateISOString(date: Date): string {
    if (date === undefined) {
        return undefined;
    }
    if (date === null) {
        return null;
    }

    return date.toLocaleDateString(
        'ja-JP',
        {
          year: 'numeric',
          month: '2-digit',
          day: '2-digit'
        }
    ).replace(/\//gi,'-');
}

EDIT : Added some undefined/null check in the method.

Yours faithfully,
LCDP

[mdoi2]

Hi, @LeComptoirDesPharmacies

Thank you for your good solution!

I don't have a philosophy on how to implement it at this time, but here are my own thoughts from a general perspective.

Since this is an auto-generated code, I think it's these three points that are important.

• Performance
• Code size
• Does not depend on other packages

That's why I like the method of adding a simple method to runtime. On the other hand, we don't want to use large libraries like moment.js as much as possible.

I hope that a solution to this challenge will be implemented in the generator.

[dfoxg]

Here is the relevant code line: https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/typescript-fetch/modelGeneric.mustache#L107

Sadly i´m dont know how fix this line.
In which status is the refactory of the typescript-fetch generator? Maybe this issue will be addressed there.

At the moment i temporary fix the generated code with following lines of code:

from queryParameters['xx'] = (requestParameters.xxas any).toISOString().substr(0,10); to queryParameters['xx'] = timeZoneOffset(requestParameters.xx as any);

function timeZoneOffset(date: Date): string {
	const offset = date.getTimezoneOffset()
	date = new Date(date.getTime() - (offset * 60 * 1000))
	return date.toISOString().split('T')[0]
}