Kotlin nullable File/FileUpload missing upload button

[BrianSetz]

I am observing some unexpected behaviour for nullable (meaning optional) File and Fileuploads.

package org.example

import jakarta.ws.rs.POST
import jakarta.ws.rs.Path
import org.eclipse.microprofile.openapi.annotations.enums.SchemaType
import org.eclipse.microprofile.openapi.annotations.media.Schema
import org.jboss.resteasy.reactive.RestForm
import org.jboss.resteasy.reactive.multipart.FileUpload
import java.io.File

@Path("/hello")
class ExampleResource {
    @POST
    @Path("/int")
    fun postInt(@RestForm int: Int): String {
        // Do nothing
        return "Int"
    }

    @POST
    @Path("/intNullable")
    fun postNullableInt(@RestForm int: Int?): String {
        // Do nothing
        return "Int?"
    }

    @POST
    @Path("/string")
    fun postString(@RestForm string: String): String {
        // Do nothing
        return "String"
    }

    @POST
    @Path("/stringNullable")
    fun postNullableString(@RestForm string: String?): String {
        // Do nothing
        return "String?"
    }

    @POST
    @Path("/file")
    fun postFile(@RestForm file: File): String {
        // Do nothing
        return "File"
    }

    @POST
    @Path("/fileNullable")
    fun postNullableFile(@RestForm file: File?): String {
        // Do nothing
        return "File?"
    }

    @POST
    @Path("/fileNullableFix")
    fun postNullableFileWithFix(@RestForm @Schema(implementation = BinaryStringSchema::class) file: File?): String {
        // Do nothing
        return "File?"
    }

    @POST
    @Path("/fileupload")
    fun postFileUpload(@RestForm fileUpload: FileUpload): String {
        // Do nothing
        return "FileUpload"
    }

    @POST
    @Path("/fileuploadNullable")
    fun postNullableFileUpload(@RestForm fileUpload: FileUpload?): String {
        // Do nothing
        return "FileUpload?"
    }

    @POST
    @Path("/fileuploadNullableFix")
    fun postNullableFileUploadWithFix(@RestForm @Schema(implementation = BinaryStringSchema::class) fileUpload: FileUpload?): String {
        // Do nothing
        return "FileUpload?"
    }
}

@Schema(type = SchemaType.STRING, format = "binary")
interface BinaryStringSchema

File (upload button):

File? (without upload button):

File? (with schema workaround):

The behaviour works as expected for nullable Ints and Strings, but it breaks for nullable Files and FileUploads (potentially others too?).

I would expect a nullable File(Upload) to have upload buttons just like non-nullable File(Upload).

[BrianSetz]

The workaround comes from a previous issue of mine: quarkusio/quarkus#39950

[MikeEdgar]

@BrianSetz I suspect this may be a bug with Swagger UI not handling the type: [ string, "null" ] in OAS 3.1.0. Can you try it with an OAS 3.0.x output? It can be generated by setting the following property.

mp.openapi.extensions.smallrye.openapi=3.0.3

[BrianSetz]

@MikeEdgar I can confirm that 3.0.3 produces the correct output!

[MikeEdgar]

As far as I can tell, this is because Swagger UI is only supporting a string value [1] for type (not an array as is the result in OAS 3.1 for a nullable file). It may be worth opening an issue (or commenting on an existing issue if there is one) to improve support for this scenario when OpenAPI 3.1 is being used. The link below is for the oas3 request body component. I do not see a separate oas31 component, which would probably be the place to start.

[1] https://github.com/swagger-api/swagger-ui/blob/96b0d361b206d34d82543a9d05fb2140fe03d881/src/core/plugins/oas3/components/request-body.jsx#L189