chenhg5/cc-connect · error

wecom-ws: image data is empty

Error message

wecom-ws: image data is empty

What it means

SendImage rejects the call when core.ImageAttachment.Data is empty (len == 0) because there are no image bytes to chunk-upload to WeCom. This is a fail-fast validation before the chunked media upload, which would otherwise fail with a less obvious 'empty media data' error inside uploadWSMedia.

Source

Thrown at platform/wecom/websocket_outbound_media.go:31

	"github.com/chenhg5/cc-connect/core"
)

const (
	wecomWSUploadChunkSize = 512 * 1024
	wecomWSUploadMaxChunks = 100
)

// SendImage uploads and sends an image through the WeCom AI Bot WebSocket API.
func (p *WSPlatform) SendImage(ctx context.Context, rctx any, img core.ImageAttachment) error {
	rc, ok := rctx.(wsReplyContext)
	if !ok {
		return fmt.Errorf("wecom-ws: SendImage: invalid reply context type %T", rctx)
	}
	if rc.chatID == "" {
		return fmt.Errorf("wecom-ws: chatID is empty, cannot send image")
	}
	if len(img.Data) == 0 {
		return fmt.Errorf("wecom-ws: image data is empty")
	}

	mediaID, err := p.uploadWSMedia(ctx, "image", wsImageFileName(img), img.Data)
	if err != nil {
		return fmt.Errorf("wecom-ws: send image: %w", err)
	}
	if err := p.sendWSMediaMessage(ctx, rc.chatID, "image", mediaID); err != nil {
		return fmt.Errorf("wecom-ws: send image: %w", err)
	}
	return nil
}

func (p *WSPlatform) uploadWSMedia(ctx context.Context, mediaType, filename string, data []byte) (string, error) {
	totalChunks := (len(data) + wecomWSUploadChunkSize - 1) / wecomWSUploadChunkSize
	if totalChunks == 0 {
		return "", fmt.Errorf("empty media data")
	}
	if totalChunks > wecomWSUploadMaxChunks {

View on GitHub (pinned to 4000b2338a)

Solutions

1. Verify img.Data is populated before calling SendImage: check the file read succeeded and len(img.Data) > 0.
2. Fix the upstream producer of the ImageAttachment (agent adapter or file loader) so it embeds actual bytes or returns an error.
3. Check that the source file on disk is non-empty and was read completely (no early EOF handling that returns nil data).
4. In tests, set Data to a small valid image payload (e.g. []byte of PNG bytes).

Example fix

// before
data, _ := os.ReadFile(path) // error ignored
core.ImageAttachment{FileName: "x.png"} // Data never set
// after
data, err := os.ReadFile(path)
if err != nil { return err }
core.ImageAttachment{FileName: "x.png", Data: data}

if len(img.Data) == 0 {
    return errors.New("cannot send image: attachment has no data")
}

if err := platform.SendImage(ctx, rctx, img); err != nil {
    if strings.Contains(err.Error(), "image data is empty") {
        // log and skip; investigate the attachment producer
    }
}

When it happens

Trigger: Calling SendImage with an ImageAttachment whose Data slice is nil or zero-length: constructing the attachment without loading file contents, a failed/cancelled file read that returned no bytes but no error, or forwarding an attachment where only metadata (filename/mime) was set.

Common situations: os.ReadFile failing silently in caller code that ignores the error and passes a nil Data; agent adapters emitting attachment metadata without inline data; test fixtures that forgot to fill Data; files of zero bytes on disk.

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

• wecom-ws: chatID is empty, cannot send image
• wecom-ws: send image: %w
• empty path
• wecom-ws: SendImage: invalid reply context type %T
• empty media data

AI-assisted analysis of chenhg5/cc-connect@4000b2338a (2026-09-06). Data as JSON: /api/errors/d78ea029a659de09. Report an issue: GitHub.