springdoc-openapi-common: Parameter reference is resolved as query parameter in generated schema

[sadam21]

Describe the bug
I'm unable to add reference to components/parameters. Fields in with query value and String schema is automatically added by OpenApiResource despite these fields are properly defined in references parameter.

To Reproduce
I wanted to create reference to parameter as described in OpenAPI specification. We have our implementation of RepositoryRestResourceProvider which creates parameter (io.swagger.v3.oas.models.parameters.Parameter)

new Parameter.$ref("someReferencedParameter")

($ref is the only parameter).

We also use OpenApiResource and the problematic code seems to be in AbstractOpenApiResource::calculatePath which contains:

if (!CollectionUtils.isEmpty(operation.getParameters()))
    operation.getParameters().forEach(parameter -> {
        if (parameter.getSchema() == null)
            parameter.setSchema(new StringSchema());
        if (parameter.getIn() == null)
            parameter.setIn(ParameterIn.QUERY.toString());
    }
);

query value and string schema is added despite it's just reference where are properly defined different values.

Expected behavior
Generated parameter in OpenAPI schema should be:

{"$ref":"#/components/parameters/someReferencedParameter"}

but was:

{"$ref":"#/components/parameters/someReferencedParameter","in":"query","schema":{"type":"string"}}

Additional context
Used Springdoc version is 1.5.0. Version 1.5.9 seems to have the same mechanism according to the source code. I tried to upgrade but there are some incompatible changes which will take some time.

I'm not sure if it's bug or feature request. Is this behaviour intended? We used workaround with subclass of Parameter:

    private class RefParameter(referenceName: String) : Parameter() {
        init {
            `$ref` = referenceName
        }
        override fun getIn(): String? {
            return null
        }

        override fun getSchema(): Schema<*>? {
            return null
        }
    }

Is there better solution?

Thank you!

[bnasslahsen]

Hi @sadam21,

It is an enhancement request, to get it out of the box.
Note that you can still achieve your goal using OpenApiCustomiser.

I propose that you submit a PR, with the related test case. And we will get it merged for the next release.

[sadam21]

Hi @bnasslahsen,

thanks for your reply.

I'll look at it and try to create some PR.