[BUG][Go] Generated go client cannot upload file

Created by: dhontecillas

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue? repo with code spec and code to reproduce
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?

Description

Have an OpenAPI v3 endpoint definition to upload a file, like the one provided in the repo, when you create the client, and try to execute an upload, you get a Invalid body type error. (You should get a connection error or similar if the client request was sent).

How to reproduce

The Makefile uses the dockerized version of the openapi-generator-cli tool, so first:

docker pull openapitools:/openapi-generator-cli

Once you have the image just run:

make buildclient

That will create a pkg/bug dir with the generated code, then run:

go run .

See the output has an "Invalid body type"

Identifying the issue

Once the code is generated, we can find the error string comes from the file pkg/bug/client.go, in the function setBody.

func setBody(body interface{}, contentType string) (bodyBuf *bytes.Buffer, err error) {
	if bodyBuf == nil {
		bodyBuf = &bytes.Buffer{}
	}

	if reader, ok := body.(io.Reader); ok {
		_, err = bodyBuf.ReadFrom(reader)
	} else if b, ok := body.([]byte); ok {
		_, err = bodyBuf.Write(b)
	} else if s, ok := body.(string); ok {
		_, err = bodyBuf.WriteString(s)
	} else if s, ok := body.(*string); ok {
		_, err = bodyBuf.WriteString(*s)
	} else if jsonCheck.MatchString(contentType) {
		err = json.NewEncoder(bodyBuf).Encode(body)
	} else if xmlCheck.MatchString(contentType) {
		err = xml.NewEncoder(bodyBuf).Encode(body)
	}

	if err != nil {
		return nil, err
	}

	if bodyBuf.Len() == 0 {
		err = fmt.Errorf("Invalid body type %s\n", contentType)
		return nil, err
	}
	return bodyBuf, nil
}

The problem is not an invalid body type, but a 0 content length.

And that happens because in pkg/bug/api_default.go file, the function to set the Body is:

func (r ApiUploadContentRequest) Body(body *os.File) ApiUploadContentRequest {
	r.body = &body
	return r
}

r.body is not of type *os.File but **os.File, see the generated struct

type ApiUploadContentRequest struct {
	ctx _context.Context
	ApiService *DefaultApiService
	body **os.File
}

so, when this part of setBody function is executed, the **os.File does not implement the io.Reader interface, and the body is not read.

	if reader, ok := body.(io.Reader); ok {
		_, err = bodyBuf.ReadFrom(reader)
	} else if b, ok := body.([]byte); ok {

openapi-generator version

latest

OpenAPI declaration file content or url

openapi.yaml in provided public repo

Generation Details

Provided a Makefile

Steps to reproduce

Provided in the description section.

Related issues/PRs

No that I know

Suggest a fix

1. Naive one is to add an if case in the client template:

	if reader, ok := body.(io.Reader); ok {
		_, err = bodyBuf.ReadFrom(reader)
	} else if readerPtr, ok := body.(*io.Reader); ok {
		_, err = bodyBuf.ReadFrom(*readrPtr)
	} else if b, ok := body.([]byte); ok {

2. Change the code generation so the body filed in the struct becomes of type *os.File

type ApiUploadContentRequest struct {
	ctx _context.Context
	ApiService *DefaultApiService
	body *os.File
}

That might involve something related with the AbstractGoCodegen.java file ?