chenhg5/cc-connect · error

weixin: empty image

Error message

weixin: empty image

What it means

Validation guard in Weixin SendImage: the image attachment's Data slice has zero length, so there are no bytes to upload to the WeChat CDN; the caller produced an empty image attachment.

Source

Thrown at platform/weixin/media_outbound.go:170

func buildVideoMessageItem(ref *cdnUploadedRef) messageItem {
	return messageItem{
		Type: messageItemVideo,
		VideoItem: &videoItem{
			Media:     mediaFromUploadRef(ref),
			VideoSize: ref.cipherSize,
		},
	}
}

// SendImage implements core.ImageSender.
func (p *Platform) SendImage(ctx context.Context, replyCtx any, img core.ImageAttachment) error {
	rc, err := p.resolveReplyContext(replyCtx)
	if err != nil {
		return err
	}
	if len(img.Data) == 0 {
		return fmt.Errorf("weixin: empty image")
	}
	ref, err := p.uploadToWeixinCDN(ctx, rc.peerUserID, img.Data, uploadMediaImage, "SendImage")
	if err != nil {
		return err
	}
	item := messageItem{
		Type: messageItemImage,
		ImageItem: &imageItem{
			Media: &cdnMedia{
				EncryptQueryParam: ref.downloadParam,
				AESKey:            formatAesKeyForAPI(ref.aesKey),
				EncryptType:       1,
			},
			MidSize: ref.cipherSize,
		},
	}
	return p.sendSingleItem(ctx, rc, item)
}

View on GitHub (pinned to 4000b2338a)

Solutions

1. Ensure the image bytes are populated (len(img.Data) > 0) before calling SendImage.
2. Fix the upstream generation/download step that produced empty image data.
3. Guard at the call site: skip or error out early when image data is empty.

Example fix

// before
data, _ := renderScreenshot() // error ignored, data empty
p.SendImage(ctx, rc, core.ImageAttachment{Data: data}) // weixin: empty image
// after
data, err := renderScreenshot()
if err != nil || len(data) == 0 { return fmt.Errorf("screenshot: %w", err) }

if len(img.Data) == 0 { return errors.New("image attachment is empty; skipping send") }

if err := p.SendImage(ctx, rc, img); err != nil && strings.Contains(err.Error(), "empty image") { log.Error("empty image produced by upstream render step") }

When it happens

Trigger: Calling SendImage with core.ImageAttachment{Data: nil} or Data: []byte{}.

Common situations: Agent produced an image attachment whose bytes failed to load (screenshot tool returned nothing); upstream decode path swallowed an error and returned empty data.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• weixin: empty file
• weixin: empty audio
• invalid remote image URL
• unsupported remote image MIME %q
• weixin: getUploadUrl: empty upload_param and upload_full_url

AI-assisted analysis of chenhg5/cc-connect@4000b2338a (2026-09-06). Data as JSON: /api/errors/6ef28ce78016ac20. Report an issue: GitHub.