[BUG] aspnetcore server cannot be compiled with async and result Task option

[robin-83]

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?
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Description

I created an ASP .NET Core server from CLI with the additonal options operationResultTask=true and operationIsAsync=true. I used the public PetStore Open API spec in the newest version (currently 1.0.17). When I try to build the solution with VS 2022 (17.4.1) an error occurs:

Schweregrad	Code	Beschreibung	Projekt	Datei	Zeile	Unterdrückungszustand
Fehler	CS4016	Da es sich um eine asynchrone Methode handelt, muss der Rückgabeausdruck vom Typ "IActionResult" anstelle von "Task" sein.	PetStore.Web	C:\Users[robin-83]\PetStore.Web9\src\PetStore.Web\Controllers\PetApi.cs	60	Aktiv

openapi-generator version

6.2.1. I have not tested this in older versions.

OpenAPI declaration file content or url

https://raw.githubusercontent.com/swagger-api/swagger-petstore/master/src/main/resources/openapi.yaml

Generation Details

openapi-generator-cli generate -i petstore.yaml -g aspnetcore -o PetStore.Web --package-name PetStore.Web --additional-properties=operationResultTask=true,operationIsAsync=true

Steps to reproduce

1. Open the solution in VS 2022
2. Rebuild

Related issues/PRs

Dont know any.

Suggest a fix

Original code:

return Task.FromResult<IActionResult>(new ObjectResult(example));

Possible fix:

return new ObjectResult(example);

[philkild]

I believe I've fixed this in #14326.

openapi-generator/modules/openapi-generator/src/main/resources/aspnetcore/3.0/controller.mustache

Line 83 in 3c41f5f

return {{#operationResultTask}}{{#operationIsAsync}}await {{/operationIsAsync}}Task.FromResult<IActionResult>({{/operationResultTask}}new ObjectResult(example){{#operationResultTask}}){{/operationResultTask}};{{/returnType}}{{^returnType}}

The return was missing the await keyword.

@philkild You have added in the aspnetcore template the ability to generate the CancellationToken.
But it depends on operationIsAsync being true.
This feels reasonable... but operationIsAsync is hard coded to false when the output is a library as per Amit Joshi 20/04/2019 commit "don't add async with library".
By the way, this detail is not covered in the doc of the generator, so this leaves users puzzled at to why the option does not work (I assume most users generate as a library)
So the fix here is either to fix the template to have the cancellationToken generated in the task case (not requiring async) OR
to NOT hard code operationIsAsync=false when the output is a library. The latter would require to ask Amit about the reason he did not want async in the library case.