d2lang/d2 · error

%v

Error message

%v

What it means

When the worker reply channel closes, runWorkers checks errhrefs for image URLs that failed to fetch. If any failed, it returns them joined as a single error via fmt.Errorf("%v", errhrefs); the caller cannot use errors.Is/As on it because it's a stringified list, not a wrapped error.

Source

Thrown at lib/imgbundler/imgbundler.go:152

					to:   bundledImage,
				}:
				}
			}()
		}
	}()

	t := time.NewTicker(time.Second * 5)
	defer t.Stop()
	for {
		select {
		case <-ctx.Done():
			return svg, fmt.Errorf("failed to wait for workers: %w", ctx.Err())
		case <-t.C:
			l.Info("fetching images...")
		case repl, ok := <-replc:
			if !ok {
				if len(errhrefs) > 0 {
					return svg, fmt.Errorf("%v", errhrefs)
				}
				return svg, nil
			}
			svg = bytes.Replace(svg, repl.from, repl.to, -1)
		}
	}
}

func worker(ctx context.Context, l simplelog.Logger, inputPath string, href []byte, isRemote, cacheImages bool) ([]byte, error) {
	if cacheImages {
		if hit, ok := imgCache.Load(string(href)); ok {
			return hit.([]byte), nil
		}
	}
	var buf []byte
	var mimeType string
	var err error
	if isRemote {

View on GitHub (pinned to 0d69dca6f5)

Solutions

1. Fix or remove the failing image URLs listed in the error output
2. Host images locally or inline them as data: URIs
3. Verify network access to those hosts (proxy config, firewall)
4. Download and reference the images via local paths to avoid remote fetch entirely

Example fix

// before (in diagram)
icon: https://internal-wiki.company/logo.svg  // 404
// after
icon: https://cdn.company.com/public/logo.svg // reachable, or data:image/svg+xml;base64,...

urls := extractImageHrefs(svg)
for _, u := range urls {
    resp, err := http.Head(u)
    if err != nil || resp.StatusCode >= 400 {
        return fmt.Errorf("image %s not fetchable (status %v)", u, statusCodeOr(err))
    }
}

svg, err := imgbundler.Bundle(ctx, svgBytes)
if err != nil {
    // err is a stringified list of failed hrefs — parse it for reporting
    if strings.Contains(err.Error(), "http") {
        log.Printf("some images failed; consider inlining them: %v", err)
    }
    return err
}

When it happens

Trigger: One or more remote image hrefs in the SVG failed to download (HTTP error, DNS failure, unsupported scheme), workers finish, channel closes, and errhrefs is non-empty.

Common situations: Diagrams referencing private/expired image URLs, hotlinks blocked by CDNs, offline environments, or URLs requiring auth/cookies.

Related errors

• failed to wait for workers: %w
• expected status 200 but got %d %s
• failed to install Playwright: %w

AI-assisted analysis of d2lang/d2@0d69dca6f5 (2026-08-31). Data as JSON: /api/errors/1f6f205ff46c61fe. Report an issue: GitHub.