chenhg5/cc-connect · error

wecom: close multipart writer: %w

Error message

wecom: close multipart writer: %w

What it means

Wrap of multipart.Writer.Close while finalizing the image upload body. Closing a multipart writer over an in-memory buffer only flushes the trailing boundary and effectively cannot fail; this wrap exists to satisfy the error contract and would only fire on internal writer-state corruption.

Source

Thrown at platform/wecom/wecom.go:560

// uploadImageMedia uploads an image to WeChat Work media API and returns the media_id.
func (p *Platform) uploadImageMedia(accessToken string, img core.ImageAttachment) (string, error) {
	name := img.FileName
	if name == "" {
		name = "image.png"
	}

	body := &bytes.Buffer{}
	writer := multipart.NewWriter(body)

	part, err := writer.CreateFormFile("media", name)
	if err != nil {
		return "", fmt.Errorf("wecom: create form file: %w", err)
	}
	if _, err := part.Write(img.Data); err != nil {
		return "", fmt.Errorf("wecom: write image data: %w", err)
	}
	if err := writer.Close(); err != nil {
		return "", fmt.Errorf("wecom: close multipart writer: %w", err)
	}

	apiURL := p.wecomAPIURL("/cgi-bin/media/upload", url.Values{
		"access_token": []string{accessToken},
		"type":         []string{"image"},
	})
	resp, err := p.apiClient.Post(apiURL, writer.FormDataContentType(), body)
	if err != nil {
		return "", fmt.Errorf("wecom: upload image: %w", err)
	}
	defer resp.Body.Close()

	var result struct {
		ErrCode int    `json:"errcode"`
		ErrMsg  string `json:"errmsg"`
		MediaID string `json:"media_id"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {

View on GitHub (pinned to 4000b2338a)

Solutions

1. Defensive only — log and skip the image upload if observed
2. No user-facing remediation; indicates memory/State corruption if it ever occurs

When it happens

Trigger: Thrown at platform/wecom/wecom.go:560 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of chenhg5/cc-connect@4000b2338a (2026-09-06). Data as JSON: /api/errors/f54ff675375990d4. Report an issue: GitHub.