[csharp] Add a server generator for FastEndpoints

[elendil-software]

This pull request add a new generator for FastEndpoints.

It allows to generate an ASP.NET server project that use FastEnpoints.

Options allows to enable some FastEndpoints functionalities like :

• RFC7807 & RFC9457 Compatible Problem Details
• Security
• Request DTO Validation
• Response Caching
• API Versioning

Related issue : #19649

Technical committee mentions @mandrean @shibayan @Blackclaws @lucamazzanti @iBicha

[elendil-software]

Just noticed an error in record generation. When a parameter is optional it should be put in the body and not in the primary constructor. I will fix that

[wing328]

thanks for the PR

please take your time fixing the bug. let us know if you need help.

[elendil-software]

please take your time fixing the bug. let us know if you need help.

I have only one point I don't know how to solve a point. Here is the edited template :

{{#operation}}
public record {{operationId}}Request({{#allParams}}
    {{#isPathParam}}{{#required}}{{&dataType}}{{#isNullable}}?{{/isNullable}} {{nameInPascalCase}}{{/required}}{{/isPathParam}}
    {{#isQueryParam}}{{#required}}[property: QueryParam] {{&dataType}} {{nameInPascalCase}}{{/required}}{{/isQueryParam}}
    {{#isBodyParam}}{{#required}}[property: FromBody] {{&dataType}} {{paramName}}{{/required}}{{/isBodyParam}}
    {{#isFormParam}}{{#required}}{{&dataType}} {{nameInPascalCase}}{{/required}}{{/isFormParam}}
    {{#isHeaderParam}}{{#required}}[property: FromHeader] {{&dataType}} {{nameInPascalCase}}{{/required}}{{/isHeaderParam}}
    {{^-last}}{{^isCookieParam}}, {{/isCookieParam}}{{/-last}}{{/allParams}})
{
{{#allParams}}
    {{#isPathParam}}{{^required}}{{&dataType}}{{#isNullable}}?{{/isNullable}} {{nameInPascalCase}} {get; init; }{{/required}}{{/isPathParam}}
    {{#isQueryParam}}{{^required}}[property: QueryParam] {{&dataType}}{{#isNullable}}?{{/isNullable}} {{nameInPascalCase}} {get; init; }{{/required}}{{/isQueryParam}}
    {{#isBodyParam}}{{^required}}[property: FromBody] {{&dataType}}{{#isNullable}}?{{/isNullable}} {{paramName}} {get; init; }{{/required}}{{/isBodyParam}}
    {{#isFormParam}}{{^required}}{{&dataType}}{{#isNullable}}?{{/isNullable}} {{nameInPascalCase}} {get; init; }{{/required}}{{/isFormParam}}
    {{#isHeaderParam}}{{^required}}[property: FromHeader] {{&dataType}}{{#isNullable}}?{{/isNullable}} {{nameInPascalCase}} {get; init; }{{/required}}{{/isHeaderParam}}
{{/allParams}}
}
{{/operation}}
{{/operations}}

My problem is : how to avoid to insert a "," in the constructor if a parameter is the last parameter that is #required or if there is not #required parameter at all.

[wing328]

My problem is : how to avoid to insert a "," in the constructor if a parameter is the last parameter that is #required or if there is not #required parameter at all.

what about using {{^-last}} ... {{/-last}}?

there are 2 more parameter lists for required and optional parameters:

• https://github.com/OpenAPITools/openapi-generator/blob/b01dd41ce354754421a2e0b9450d217eeaecf304/modules/openapi-generator/src/main/resources/elixir/api.mustache#L23
• https://github.com/OpenAPITools/openapi-generator/blob/b01dd41ce354754421a2e0b9450d217eeaecf304/modules/openapi-generator/src/main/resources/elixir/api.mustache#L27

would these help?

[devhl-labs]

There is also a join with comma lambda.

[elendil-software]

My problem is : how to avoid to insert a "," in the constructor if a parameter is the last parameter that is #required or if there is not #required parameter at all.

what about using {{^-last}} ... {{/-last}}?

there are 2 more parameter lists for required and optional parameters:

* https://github.com/OpenAPITools/openapi-generator/blob/b01dd41ce354754421a2e0b9450d217eeaecf304/modules/openapi-generator/src/main/resources/elixir/api.mustache#L23

* https://github.com/OpenAPITools/openapi-generator/blob/b01dd41ce354754421a2e0b9450d217eeaecf304/modules/openapi-generator/src/main/resources/elixir/api.mustache#L27

would these help?

Perfect. Done.

[elendil-software]

Not sure how to fix this error on action execution : https://github.com/OpenAPITools/openapi-generator/actions/runs/11091036118/job/30820196576#logs

@@ -1,7 +1,6 @@
 using FastEndpoints;
 
 using Org.OpenAPITools.Models;
-using Order = Org.OpenAPITools.Models.Order;
 
 namespace Org.OpenAPITools.Features;

To get the project built the line using Order = Org.OpenAPITools.Models.Order; need to be added manually. This is because both the model and FastEnpoint have a classe named Order

 -Project("{F0A8E8AF-E927-46D2-8D4C-2402A9559FBE}") = "Org.OpenAPITools", "Org.OpenAPITools\Org.OpenAPITools.csproj", "{11A46A2A-1367-4B2E-8FBA-121D75FB3192}"
+Project("{BB2B4493-3AE6-4AE7-BCC1-DA8D3C721BFC}") = "Org.OpenAPITools", "Org.OpenAPITools\Org.OpenAPITools.csproj", "{F25EF962-61BB-4618-82C7-FB72A5B7AB52}"

These GUID are created by the generator. I could give them a default value and let the user to choose if he want to generate new values

[wing328]

FastEnpoint have a classe named Order

any convention in naming the FastEndpoint class?

In other server generators, we usually add "Api" as the suffix to avoid name collision with model names.

[elendil-software]

FastEnpoint have a classe named Order

any convention in naming the FastEndpoint class?

In other server generators, we usually add "Api" as the suffix to avoid name collision with model names.

The convention are to add a "Request" suffix for the requests, which is what I have done. The "Response" suffix is used for the responses. That is what I have done too, but I revert it back. The reason is that when using the generator a model can also be used as the body of a request. And a request containing a property of type "SomethingResponse" didn't make any sense.

Maybe I could generate two models, one with a suffix "Response" and an other with, maybe, "Body" suffix. The drawback, I think, is that some classes could not be used at all.

[elendil-software]

While checking again the required parameter and testing with a "real" open-api yaml file I noticed that some required parameters are not genereated as required.

I don't know if I made a mistake or miss something but looks like that parameter that are of form type are not included in the required parameters.

Here is a part of the yaml :

requestBody:
        content:
          application/x-www-form-urlencoded:
            schema:
              allOf:
                - $ref: '#/components/schemas/AlpacaRequest'
                - properties:
                    Action:
                      description: >-
                        A well known name that represents the action to be carried
                        out.
                      type: string
                    Parameters:
                      description: >-
                        List of required parameters or an Empty String if none are
                        required
                      type: string
                  required:
                    - Action
                    - Parameters

[elendil-software]

FastEnpoint have a classe named Order

any convention in naming the FastEndpoint class? In other server generators, we usually add "Api" as the suffix to avoid name collision with model names.

The convention are to add a "Request" suffix for the requests, which is what I have done. The "Response" suffix is used for the responses. That is what I have done too, but I revert it back. The reason is that when using the generator a model can also be used as the body of a request. And a request containing a property of type "SomethingResponse" didn't make any sense.

Maybe I could generate two models, one with a suffix "Response" and an other with, maybe, "Body" suffix. The drawback, I think, is that some classes could not be used at all.

I have tried, adding a suffix will do. I only have a problem. How to handle the case when the model is used in a list.

if I do something like : public {{&dataType}}Model {{paramName}} { get; set; } I get : public List<User>Model user { get; set; } How can I get : public List<UserModel> user { get; set; } ?

[wing328]

I only have a problem. How to handle the case when the model is used in a list.

for model, i wouldn't recommend using a suffix by default

for endpoints, looks like adding a suffix like "Request" to avoid the naming collision with models if I understand it correctly.

[elendil-software]

I only have a problem. How to handle the case when the model is used in a list.

for model, i wouldn't recommend using a suffix by default

for endpoints, looks like adding a suffix like "Request" to avoid the naming collision with models if I understand it correctly.

No, in this case, the collision is because both FastEndpoints and the generated project provide a type with the same name:

Generated requests and endpoints already have a suffix.

[wing328]

ok. thanks for the details

2 ways to handle this kinda siutation:

• use fully qualified name for FastEndpoints in the auto-generated code
• add those names to reserved keyword list (e.g. Order will become ModelOrder, or users can use modelNameMapping option to name Order as something else, e.g. GeneralOrder)

[devhl-labs]

Use a fully qualified name. We ought to be using fully qualified names everywhere, but we don't for some reason.

[elendil-software]

ok. thanks for the details

2 ways to handle this kinda siutation:

* use fully qualified name for FastEndpoints in the auto-generated code

* add those names to reserved keyword list (e.g. Order will become ModelOrder, or users can use modelNameMapping option to name Order as something else, e.g. GeneralOrder)

I used a fully qualified name. And I added option to set the GUID use in the solution file.

Hope everything works now.

[wing328]

https://github.com/OpenAPITools/openapi-generator/actions/runs/11312510702/job/31462379731?pr=19690

please update the samples when you've time

[elendil-software]

https://github.com/OpenAPITools/openapi-generator/actions/runs/11312510702/job/31462379731?pr=19690

please update the samples when you've time

Not sure how to solve that. Even after having updated the sample I still have 7.9.0-SNAPSHOTin VERSION files

[elendil-software]

https://github.com/OpenAPITools/openapi-generator/actions/runs/11312510702/job/31462379731?pr=19690 please update the samples when you've time

Not sure how to solve that. Even after having updated the sample I still have 7.9.0-SNAPSHOTin VERSION files

@wing328 Solved. It was an issue with my dev environment. OK after clearing the IDE cache.

[elendil-software]

@wing328 Is there something more I need to correct on this PR ?

[wing328]

https://github.com/OpenAPITools/openapi-generator/actions/runs/11392557217/job/32653087692?pr=19690

i'll fix it after merging this PR

UPDATE: done via 28e02fc1a2b