Data: handle any type gracefully based on "Content-Type" of headers

[wenchy]

requests/request.go

Lines 80 to 95 in cbe3a6b

	// requestData sends an HTTP request to the specified URL, with raw string
	// as the request body.
	func requestData(c *Client, method, url string, opts *Options) (*Response, error) {
	body := bytes.NewBuffer(nil)
	if opts.Data != nil {
	d := fmt.Sprintf("%v", opts.Data)
	_, err := body.WriteString(d)
	if err != nil {
	return nil, err
	}
	}
	// TODO: judge content type
	// opts.Headers["Content-Type"] = "application/x-www-form-urlencoded"
	opts.Body = body
	return c.request(method, url, opts, body.Bytes())
	}

Problem

r, err := requests.Post("http://example.com",   
        requests.Data(`{"group":1,"version":"v1.0"`))
if err != nil {
    // ...
}

vs

r, err := requests.Post("http://example.com",   
        requests.Data([]byte(`{"group":1,"version":"v1.0"`)))
if err != nil {
    // ...
}

The underlying d := fmt.Sprintf("%v", opts.Data) is a problem. We should firstly decide the data type based on "Content-Type" of headers. Refer to https://github.com/go-resty/resty/blob/v3/middleware.go#L414

For examples:

1. The user specifies "Content-Type" explicitly, then

• "application/x-www-form-urlencoded" or "text/plain": treat data as string d := fmt.Sprintf("%s", opts.Data)
• "application/octet-stream": treat data as bytes d := fmt.Sprintf("%v", opts.Data)
• more content types...

2. Other, if user does not specify "Content-Type" explicitly, then assert type swich on the data type

• string
• []byte
• ...

Test

Keep sure the following two cases are the same HTTP request.

r, err := requests.Post("http://example.com",   
        requests.Data(`{"group":1,"version":"v1.0"`))
if err != nil {
    // ...
}

vs

r, err := requests.Post("http://example.com",   
        requests.Data([]byte(`{"group":1,"version":"v1.0"`)))
if err != nil {
    // ...
}

References

• https://github.com/go-resty/resty/blob/v3/middleware.go#L414
• https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/MIME_types