Cannot create optional `file` type in openapi-generator

[grokify]

in	spec	results
formData	optional array of files	doesn't work
formData	optional single file	doesn't work
formData	required array of files	doesn't work
formData	required single file	works

The openapi-generator spec does have an optional single file endpoint:

https://github.com/OpenAPITools/openapi-generator/blob/master/samples/client/petstore/go/go-petstore/api/swagger.yaml

Optional Array of Files

YAML spec

          -
            name: "attachment"
            in: "formData"
            description: "File to upload"
            required: false
            type: "array"
            items:
              type: "file"

Generated Code

     * @param "Attachment" (optional.Interface of []*os.File) -  File to upload

type SendFaxMessageOpts struct {
	Attachment    optional.Interface
	FaxResolution optional.String
	SendTime      optional.Time
	IsoCode       optional.String
	CoverIndex    optional.Int32
	CoverPageText optional.String
}

	if localVarOptionals != nil && localVarOptionals.Attachment.IsSet() {
		localVarFormParams.Add("attachment", parameterToString(localVarOptionals.Attachment.Value(), "csv"))
	}

Runtime Error

./fax_send.go:130:21: cannot use files (type []*os.File) as type optional.Interface in assignment

Optional Single File

YAML Spec

          -
            name: "attachment"
            in: "formData"
            description: "File to upload"
            required: false
            type: "file"

     * @param "Attachment" (optional.Interface of *os.File) -  File to upload

type SendFaxMessageOpts struct {
	Attachment    optional.Interface
	FaxResolution optional.String
	SendTime      optional.Time
	IsoCode       optional.String
	CoverIndex    optional.Int32
	CoverPageText optional.String
}

	var localVarFile *os.File
	if localVarOptionals != nil && localVarOptionals.Attachment.IsSet() {
		localVarFileOk := false
		localVarFile, localVarFileOk = localVarOptionals.Attachment.Value().(*os.File)
		if !localVarFileOk {
			return localVarReturnValue, nil, reportError("attachment should be *os.File")
		}
	}
	if localVarFile != nil {
		fbs, _ := ioutil.ReadAll(localVarFile)
		localVarFileBytes = fbs
		localVarFileName = localVarFile.Name()
		localVarFile.Close()
	}

Runtime Error

./fax_send.go:130:21: cannot use files[0] (type *os.File) as type optional.Interface in assignment

Required Array of Files

Compile time error

../../client/api_messages.go:633:131: undefined: os

After resolving the "os" import:

	localVarFormParams.Add("attachment", parameterToString(attachment, "csv"))