Upon further investigation, this seems to be a class of errors related to the code generation of enum types (Swagger spec collectionFormat: "multi"). In the swagger spec, whenever we have an enum that gets mapped to a map[string]interface{}, a type assertion for []string is made, when it should be string.

I'm not familiar with the code generation, but if you point me in the right direction, I'd be willing to contribute a more permanent fix.

Generally I do a few things to fix the auto-generated code:

• Bugs in the Swagger spec (swagger_spec.yaml) are fixed in the spec so the code can be auto-generated again.
• Bugs in Swagger Codegen are (a) fixed in swagger_codegen_command.sh post processing and then (b) reported to the https://github.com/swagger-api/swagger-codegen project such as: [Golang] date-time query parameter does not produce a RFC 3339 time per spec definition swagger-api/swagger-codegen#8039

By providing the changes in the Swagger spec and post-generation commands, the changes will persist after rebuilds with an updated spec.

While it's an inconvenience for two of the parameters, it completely breaks incremental sync functionality.

I agree this isn't necessary when there are only two enumerated values, since both values is equivalent to specifying no values. For these, one approach would be to remove collectionType.

While most occurrences only have 2 values, listExtensionPhoneNumbers / extension/phone-number has more:

            collectionFormat: "multi"
            enum:
              - "MainCompanyNumber"
              - "AdditionalCompanyNumber"
              - "CompanyNumber"
              - "DirectNumber"
              - "CompanyFaxNumber"
              - "ForwardedNumber"

I just finished upgrading the SDK to use OpenAPI Generator. It's a fork of Swagger Codegen with a benefit of more frequent releases so we can see about getting support for this in. I'll spend some time looking into this and may be able to provide some info on how to proceed.

You can learn more about the project here:

https://github.com/OpenAPITools/openapi-generator

For this investigation, I'll use listExtensionPhoneNumbers as the example.

Here's the spec:

          -
            name: "usageType"
            in: "query"
            description: "Usage type of the phone number"
            required: false
            type: "array"
            items:
              type: "string"
            collectionFormat: "multi"
            enum:
              - "MainCompanyNumber"
              - "AdditionalCompanyNumber"
              - "CompanyNumber"
              - "DirectNumber"
              - "CompanyFaxNumber"
              - "ForwardedNumber"

Here's the generated code:

type ListExtensionPhoneNumbersOpts struct {
	UsageType optional.Interface
	Page      optional.Int32
	PerPage   optional.Int32
}

	if localVarOptionals != nil && localVarOptionals.UsageType.IsSet() {
		localVarQueryParams.Add("usageType", parameterToString(localVarOptionals.UsageType.Value(), "multi"))
	}

It seems like the desired code would be:

type ListExtensionPhoneNumbersOpts struct {
	UsageType optional.SliceString
	Page      optional.Int32
	PerPage   optional.Int32
}

	if localVarOptionals != nil && localVarOptionals.UsageType.IsSet() {
                for _, s := range localVarOptionals.UsageType.Value() {
			localVarQueryParams.Add("usageType", parameterToString(localVarOptionals.UsageType.Value(), "multi"))
                }
	}

optional is a library by antihax that handles Go's non-null zero values: https://github.com/antihax/optional

Different collection formats are here:

https://github.com/OAI/OpenAPI-Specification/blob/master/versions/2.0.md