What causes "line %d: %w" in glanceapp/glance?

Open glance.yml at the reported line and read the widget's type field

line %d: %w

Error message

line %d: %w

What it means

While unmarshalling the widgets list of a page, creating a widget (almost always the unknown-type error) failed, and the error is re-wrapped with the YAML node's line number. The line points at the offending widget block in glance.yml so you can jump straight to the bad entry.

Source

Thrown at internal/glance/widget.go:113

func (w *widgets) UnmarshalYAML(node *yaml.Node) error {
	var nodes []yaml.Node

	if err := node.Decode(&nodes); err != nil {
		return err
	}

	for _, node := range nodes {
		meta := struct {
			Type string `yaml:"type"`
		}{}

		if err := node.Decode(&meta); err != nil {
			return err
		}

		widget, err := newWidget(meta.Type)
		if err != nil {
			return fmt.Errorf("line %d: %w", node.Line, err)
		}

		if err = node.Decode(widget); err != nil {
			return err
		}

		*w = append(*w, widget)
	}

	return nil
}

type widget interface {
	// These need to be exported because they get called in templates
	Render() template.HTML
	GetType() string
	GetID() uint64

View on GitHub (pinned to 91324e8de7)

Solutions

Open glance.yml at the reported line and read the widget's type field
Correct or remove the type value per the inner error message
Re-run glance (or reload config) to confirm the page parses

Example fix

# glance.yml, at the reported line:
# before (line 42)
- type: serverstats

# after
- type: server-stats

Defensive patterns

Strategy: validation

Type guard

func isWidgetLineErr(err error) bool {
	var lineErr interface{ error }
	_ = lineErr
	return err != nil && strings.HasPrefix(err.Error(), "line ")
}

Try / catch

if err := yaml.Unmarshal(data, &pages); err != nil {
    if isWidgetLineErr(err) {
        // parse 'line N' out of the message and point the user at that entry in glance.yml
        log.Printf("config error near %s — check the type field there", err)
    }
    os.Exit(1)
}

Prevention

Use the line number in the message to jump directly to the broken block instead of bisecting the file
Validate the full config with `glance validate`-style checks (or a dry parse) after edits

When it happens

Trigger: Any widget node on the indicated line whose type value does not match a known widget; the line number is where that widget mapping starts in the YAML file.

Common situations: Large config files where finding the bad block is hard; the line number plus the inner 'unknown widget type: X' message together pinpoint the exact entry to fix.

Related errors

AI-assisted analysis of glanceapp/glance@91324e8de7 (2026-08-15). Data as JSON: /api/errors/ac44bed2ad1972fa. Report an issue: GitHub.