Default value handling for parameters

[shota3506]

Hello 👋

We are using the OapiRequestValidator middleware for validation.

kin-openapi handles default values for parameters by adding value to *http.Request.URL.RawQuery if a parameter is not set.

However, the server code generated by oapi-codegen parses parameters before applying the middleware. This means that any changes made to *http.Request within the middleware (like setting default values via kin-openapi) will not be reflected in the parsed parameters.

I was hoping that using middleware could help with default value handling, based on this comment:
oapi-codegen/oapi-codegen#138 (comment)
Is there a workaround for this issue? Specifically, how can we ensure that default values set by kin-openapi's validator are set in the params generated by oapi-codegen?

[LuccaBitfly]

I've run into the same issue. Wrapping the validation middleware around the handler, instead of setting it in the handler options, might work for you:

validationMiddleware := nethttpmiddleware.OapiRequestValidatorWithOptions(spec, &nethttpmiddleware.Options{
	Options: openapi3filter.Options{
		// ...
	},
})
handler := gen.HandlerWithOptions(myServer, gen.StdHTTPServerOptions{
	// ...
})
handler = validationMiddleware(handler) // <- defaults should get applied before server reads HTTP request

Though I agree that it should work without this workaround.