Nswag: TypeScript Fetch client generator error with WrapResponses enabled

[leon-imagineers]

The TypeScript Fetch client generator with promises seems to cause some strange behaviour compared to for example the Angular2 client generator with the same options when handling 204 responses from a delete endpoint with the option WrapResponses = enabled.

For example, the Fetch client generator generates the following code to handle the 204 response:

if (status === 204) {
    return response.text().then((_responseText) => {
    return;
    });
}

Which will throw an error because the generated ProcessDelete method expects a return of type Promise<SwaggerResponse<void>>.

While the Angular2 generator generates the following code, with the same endpoint and the same generator settings:

if (status === 204) {
    const _responseText = response.text();
    return Observable.of<SwaggerResponse<void>>(<any>null);
}

Which is a valid return for the generated ProcessDelete method.

These are the settings i am using for respectively the fetch and angular generator:

new SwaggerToTypeScriptClientGeneratorSettings
            {
                ClassName = "{controller}Client",
                PromiseType = PromiseType.Promise,
                BaseUrlTokenName = "API_BASE_URL",
                ImportRequiredTypes = true,
                Template = TypeScriptTemplate.Fetch,
                WrapResponses = true,
                TypeScriptGeneratorSettings =
                {
                    MarkOptionalProperties = true,
                    TypeScriptVersion = 2.0m,
                }
            };

new SwaggerToTypeScriptClientGeneratorSettings
            {
                ClassName = "{controller}Client",
                Template = TypeScriptTemplate.Angular,
                GenerateOptionalParameters = true,
                WrapResponses = true,
                TypeScriptGeneratorSettings =
                {
                    TypeScriptVersion = 2.0m,
                }
            };

Am i doing/understanding something wrong or is this a bug in the fetch client generator template?

If you need any more information please let me know.

Thanks in advance

[RicoSuter]

This is probably a bug - I dont use WrapResponses in any of my projects, so this is not as well tested as the other options... I even think that the angular code is wrong - it should always return a SwaggerResponse and never null...

[leon-imagineers]

Thanks for the quick response!

If i understand correctly, the following code https://github.com/RSuter/NSwag/blob/21a5f65f44f8136e91df2ba01f1d4ae71781572b/src/NSwag.CodeGeneration.TypeScript/Templates/Client.ProcessResponse.HandleStatusCode.liquid#L57-L64
would need to be changed to also have an option for isFetchOrAurelia? If so, i will see if i can fix this

[RicoSuter]

Yes but only in the case of WrapResponses... if the setting is off then it is correct...

[RicoSuter]

I think your code selection should be replaced by

{%     elseif response.IsSuccess -%}
{%         if operation.WrapResponse -%}
{%             if IsAngular -%}
return Observable.of<{{ operation.ResultType }}>(<any>null);
{%             elseif IsAngularJS -%}
return this.q.resolve<{{ operation.ResultType }}>(<any>null);
{%             else -%}
return{% if operation.HasResultType %} null{% endif %};
{%             endif -%}
{%         else -%}
{%             if IsAngular -%}
return Observable.of<{{ operation.ResultType }}>(<any>null);
{%             elseif IsAngularJS -%}
return this.q.resolve<{{ operation.ResultType }}>(<any>null);
{%             else -%}
return{% if operation.HasResultType %} null{% endif %};
{%             endif -%}
{%         endif -%}
{%     else -%}

where the first part (if operation.WrapResponse) must be fixed

[RicoSuter]

I think this could work:

{%     elseif response.IsSuccess -%}
{%         if operation.WrapResponse -%}
{%             if IsAngular -%}
return Observable.of<{{ operation.ResultType }}>(new {{ operation.ResponseClass }}(status, _headers, <any>null));
{%             elseif IsAngularJS -%}
return this.q.resolve<{{ operation.ResultType }}>(new {{ operation.ResponseClass }}(status, _headers, <any>null));
{%             else -%}
return new {{ operation.ResponseClass }}(status, _headers, <any>null);
{%             endif -%}
{%         else -%}
{%             if IsAngular -%}
return Observable.of<{{ operation.ResultType }}>(<any>null);
{%             elseif IsAngularJS -%}
return this.q.resolve<{{ operation.ResultType }}>(<any>null);
{%             else -%}
return{% if operation.HasResultType %} null{% endif %};
{%             endif -%}
{%         endif -%}
{%     else -%}

[RicoSuter]

You can test this by overriding the template: https://github.com/RSuter/NSwag/wiki/Templates
Then report back here or create a PR..

[leon-imagineers]

Thank you, the provided code seems to work without problems in my project as far as i can see

[RicoSuter]

@quails4Eva @ml-dev @BringerOD

Can you verify?

I think WrapResponse should always return a response object and never null, what do you think?

[RicoSuter]

Ref https://github.com/RSuter/NSwag/issues/600 https://github.com/RSuter/NSwag/pull/894

[ml-dev]

@RSuter
I would agree that WrapResponse should always return a response object and never null.

[quails4Eva]

I haven't been working on the project that uses this recently, but I agree that it shouldn't return null.

[RicoSuter]

Please retest with latest CI artifacts