How can we handle multi-part request to add "file" in the request?

[wangmir]

Same as title.

When I wanna send file with Upload scalar, (https://gqlgen.com/reference/file-upload/)
How can we send this request?

Is there any features to support multi-part request on this library? or should I manually add that.

[hgiasac]

Hi @wangmir ,

This library only supports JSON content type. I have no idea if there is another supported graphql client in Go. However, you can use a plain HTTP client to write a simple request with mime/multipart body.

[wangmir]

Hi @hgiasac ,

Yes, but I just wanted to utilize the rich functionalities of this library.

When I check the code, I think we can still reuse some of the code, and maybe similar to the requestModifier approach, we can make a custom byte buffer on this.

from below code,

// Request the common method that send graphql request
func (c *Client) request(ctx context.Context, query string, variables map[string]interface{}, options ...Option) ([]byte, *http.Response, io.Reader, Errors) {
	in := GraphQLRequestPayload{
		Query:     query,
		Variables: variables,
	}
	var buf bytes.Buffer
	err := json.NewEncoder(&buf).Encode(in)
	if err != nil {
		return nil, nil, nil, Errors{newError(ErrGraphQLEncode, err)}
	}

	reqReader := bytes.NewReader(buf.Bytes())
	request, err := http.NewRequestWithContext(ctx, http.MethodPost, c.url, reqReader)
	if err != nil {
		e := newError(ErrRequestError, fmt.Errorf("problem constructing request: %w", err))
		if c.debug {
			e = e.withRequest(request, reqReader)
		}
		return nil, nil, nil, Errors{e}
	}
	request.Header.Add("Content-Type", "application/json")

	if c.requestModifier != nil {
		c.requestModifier(request)
	}

	resp, err := c.httpClient.Do(request)
	// ... rest of the code    
}

We can make the below part as the default byte buffer writer. The input will be GraphQLRequestPayload

	var buf bytes.Buffer
	err := json.NewEncoder(&buf).Encode(in)
	if err != nil {
		return nil, nil, nil, Errors{newError(ErrGraphQLEncode, err)}
	}

And, when I want to make multi-part request, then we can just customize this byte buffer to do something like,

var b bytes.Buffer
	w := multipart.NewWriter(&b)

	// Add the query and variables fields
	fw, err := w.CreateFormField("operations")
	if err != nil {
		fmt.Println("Error creating form field: ", err)
		return
	}
	_, _ = fw.Write([]byte(`{"query":"mutation ($input: PostInput!) { createPost(input: $input) { id, title, fileUrl } }","variables":{"input":{"title":"My Title","file":null}}}`))

	fw, err = w.CreateFormField("map")
	if err != nil {
		fmt.Println("Error creating form field: ", err)
		return
	}
	_, _ = fw.Write([]byte(`{"0":["variables.input.file"]}`))

	// Add the file field
	file, err := os.Open(tmpFile.Name())
	if err != nil {
		fmt.Println("Error opening file: ", err)
		return
	}
	defer file.Close()

	fw, err = w.CreateFormFile("0", tmpFile.Name())
	if err != nil {
		fmt.Println("Error creating form file: ", err)
		return
	}
	_, _ = io.Copy(fw, file)

	// Don't forget to close the multipart writer.
	w.Close()

How about that?

If u agree, then I can make a PR to fix this.

[hgiasac]

I get your idea. Feel free to make a PR.
However, you need to make sure the change doesn't break the current interface and API design.