d2lang/d2 · error

expected "underline" to be true or false

Error message

expected "underline" to be true or false

What it means

D2's style-setting code parses the "underline" style value with strconv.ParseBool; invalid values return this error and the style is skipped. Applies only when s.Underline is non-nil.

Source

Thrown at d2graph/d2graph.go:462

			return errors.New(`expected "bold" to be true or false`)
		}
		s.Bold.Value = value
	case "italic":
		if s.Italic == nil {
			break
		}
		_, err := strconv.ParseBool(value)
		if err != nil {
			return errors.New(`expected "italic" to be true or false`)
		}
		s.Italic.Value = value
	case "underline":
		if s.Underline == nil {
			break
		}
		_, err := strconv.ParseBool(value)
		if err != nil {
			return errors.New(`expected "underline" to be true or false`)
		}
		s.Underline.Value = value
	case "filled":
		if s.Filled == nil {
			break
		}
		_, err := strconv.ParseBool(value)
		if err != nil {
			return errors.New(`expected "filled" to be true or false`)
		}
		s.Filled.Value = value
	case "double-border":
		if s.DoubleBorder == nil {
			break
		}
		_, err := strconv.ParseBool(value)
		if err != nil {
			return errors.New(`expected "double-border" to be true or false`)

View on GitHub (pinned to 0d69dca6f5)

Solutions

1. Change the value to "true" or "false" (e.g. `x.underline: true`).
2. Use 1 or 0 as accepted boolean numerics.
3. Remove the underline key to keep default text decoration.
4. Normalize user input to "true"/"false" before passing it into the style setter.

Example fix

// before (D2)
x: my shape
x.underline: on
// after
x: my shape
x.underline: true

func validStyleBool(v string) bool {
	_, err := strconv.ParseBool(v)
	return err == nil
}
// before applying: if !validStyleBool(underlineVal) { /* fix or reject */ }

func isParseBoolValue(s string) bool {
	switch s {
	case "1", "t", "T", "TRUE", "true", "True", "0", "f", "F", "FALSE", "false", "False":
		return true
	}
	return false
}

if err := obj.SetStyle("underline", val); err != nil {
	if strings.Contains(err.Error(), `"underline" to be true or false`) {
		// fallback: no underline
		val = "false"
	}
}

When it happens

Trigger: Setting style key "underline" to a value strconv.ParseBool rejects, e.g. `x.underline: yes` or `underline: on`.

Common situations: Users write "yes"/"on" for underlined text or reuse CSS-style values like "underline"/"line-through" instead of booleans.

Related errors

• expected "shadow" to be true or false
• expected "3d" to be true or false
• expected "multiple" to be true or false
• expected "animated" to be true or false
• expected "bold" to be true or false

AI-assisted analysis of d2lang/d2@0d69dca6f5 (2026-08-31). Data as JSON: /api/errors/237df2d5d9df98b5. Report an issue: GitHub.