csharp Warnings with x-www-form-urlencoded and array parameters

[johnwc]

Based on the closed issue #2291 and #219 is the c# serializer working for form data arrays?

When I try to generate a client using a schema that has application/x-www-form-urlencoded and parameters with type set as array, I get the following warning.

warn: Kiota.Builder.KiotaBuilder[0]
      OpenAPI warning: #/paths/~1reports~1deal_time_to_close/post - The operation postReportsDealTimeToClose has a request body which is not an object type. This is not supported by Kiota and serialization will fail.
warn: Kiota.Builder.KiotaBuilder[0]
      OpenAPI warning: #/paths/~1reports~1deal_time_to_close/post - The operation postReportsDealTimeToClose has a request body with a complex properties and the url form encoded content type. This is not supported by Kiota and serialization of complex properties will fail.

        "produces": [
          "application/json"
        ],
        "consumes": [
          "application/x-www-form-urlencoded"
        ],
        "parameters": [
          {
            "in": "formData",
            "name": "filters[created_at][]",
            "description": "Filter deals by created_at (accepts min/max unix timestamps i.e [1698084670, 1698105600]",
            "type": "array",
            "items": {
              "type": "integer",
              "format": "int32"
            },
            "required": false
          }
        ],

[baywet]

Thanks for trying kiota and for reaching out.
Can you confirm which version of Kiota you are using? I've just tried on the latest and it seems to be working fine.
Also I can't find a reference to this error message in the code.

[johnwc]

Using Kiota tool 1.7.0, it seems to be here https://github.com/microsoft/kiota/blob/main/src/Kiota.Builder/Validation/UrlFormEncodedComplex.cs

> kiota --version
1.7.0+1d6d0257e38694f73e64f0412739250c6d3722f1

[baywet]

Thanks for the additional information. I missed the fact that your schema is using an array. The reason why we don't support arrays is because there's no standard way of serializing them:

• one could explode the parameter i.e. property=value1&property=value2
• one could use CSV representation i.e property=value1,value2 in which case, what should the separate be? (, ; ...)
• one could use a JSON representation i.e property=["value1","value2"] in which case the value probably needs to be uri encoded as well
• ...

For reference, we added this validation rule with this issue #2019

[johnwc]

@baywet but it does do arrays, it does them as duplicate variables like your first example. See links below. And, the OpenAPI has the option (collectionFormat) to tell the client how it expects the array to be passed, with csv being the default.

https://github.com/microsoft/kiota-serialization-form-dotnet/blob/main/src/FormSerializationWriter.cs#L81
https://github.com/microsoft/kiota-serialization-form-dotnet/blob/main/src/FormSerializationWriter.cs#L110

[baywet]

Thanks for pointing this out, I think I got confused. @andrueastman I know we talked about this at length in the past. Between this in dotnet, and that typescript PR I believe my last statement was wrong.
Do you see any reason why the validation rule should keep warning for collections?

[johnwc]

Shouldn't the serializer be updated to read the collectionFormat value to know how to write the arrays?

[baywet]

The equivalent of which is form with explode in OAS v3. The challenge being we're not carrying the explode information and we actually have a divergence of implementation:

• enum collection are written as csv
• string collection are written as exploded values

this is related to #3238

Let's focus on the generation for a bit, in your scenario, while trying to reproduce it, I was getting the warning, but at least I was getting the generated code out, is that your experience as well?

[johnwc]

Yes, that is my experience as well. Luckily the default behavior to write multiple var=value to the form data is how the API is expecting the data. But if it was expecting it to be csv, we would have issues having Kiota as an option for generating API clients.

[baywet]

thanks for confirming, so I'm guessing the first step is to remove the validation for arrays. And then once this is done, later in #3238 we'll normalize the explode behaviour based on the information that needs to be passed (which we can't pass today without resulting in a breaking change)

[baywet]

Update: for the validation rule fix I put together #3593.
I also found a bug in the parsing library we use and put together microsoft/OpenAPI.NET#1444, until that bug is merged, released, and kiota grabs the latest release, you'll still get one of the warnings.
For the explode information, and for the normalization, we'll need to wait until v2 since it'd require a breaking change.

[johnwc]

Can you explain the breaking change, and why defaults that are already being assumed can't be put in place?

[baywet]

This method needs to be passed the explode information. This would result in adding an additional parameter to the method to drive the different in behavior.
Because this method is defined in an interface, the change would mean a binary breaking change.