Cannot support APIs that have path parameters that use reserved characters that must not be percent encoded.

[darrelmiller]

Currently OpenAPI does not allow Path parameters to use the allowReserved property. This is a problem for APIs that want to use these characters in their APIs. The NightScout v2 API is an example where it uses a comma separated list of values in a path segment.
However, UriTemplates do allow this. https://www.rfc-editor.org/rfc/rfc6570#section-3.2.3

We need to invent a x-AllowReserved as a workaround. OpenAPI didn't allow it because it would make it possible for a parameter to introduce new path segments. That would make operation resolution non-deterministic.

[darrelmiller]

The x-AllowReserved: true property in the OpenAPI would cause the parameter to be rendered as {+myparam} in the path parameter. The + character will prevent reserved characters from being escaped when serializing the parameter value.

[darrelmiller]

After testing with Microsoft Graph we identified that the one place we know of that uses reserved characters in a path parameter, the gateway successfully handles this scenario.
e.g.

https://graph.microsoft.com/v1.0/me/drive/root%3A%2Fattachments%3A/children

Therefore we can move this issue to 1.2.

[baywet]

@darrelmiller, since we don't have "customer demand" for this, and since this is blocked by dependencies, are you ok with moving it to 1.4 for now?

[baywet]

If I understand this issue correctly we'd need to:

1. come up with an extension for path parameters https://github.com/microsoft/OpenAPI/tree/main/extensions that documents whether or not reserved expansion is allowed
2. come up with an OData annotation that documents that aspect
3. implement the conversion of that annotation to the extension
4. implement parsing the extension in kiota, and add a + when projecting the path parameter into the template
5. add an XSLT "fix" for the CSDL to insert the annotation
   Correct?

[darrelmiller]

We don't need this for Graph so we don't need step 2, 3 or 5. Just 1 + 4. I'm fine if we push this to a late milestone due to lack of customer requests.

[baywet]

Thanks for the precision. It's a small change then I'll go ahead and document the extension and follow up with implementation. Let's leave it in 1.6 for now.