What causes "expected "double-border" to be true or false" in d2lang/d2?

Change the value to exactly `true` or `false` (also accepted: 1/0, T/F, TRUE/FALSE case-insensitively).

expected "double-border" to be true or false

Error message

expected "double-border" to be true or false

What it means

This error comes from applying the `double-border` style to a shape in d2graph. The value assigned to `double-border` must parse as a boolean (true/false); strconv.ParseBool failed, so the value was rejected before being stored on the style.

Source

Thrown at d2graph/d2graph.go:480

			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`)
		}
		s.DoubleBorder.Value = value
	case "text-transform":
		if s.TextTransform == nil {
			break
		}
		if !go2.Contains(d2ast.TextTransforms, strings.ToLower(value)) {
			return fmt.Errorf(`expected "text-transform" to be one of (%s)`, strings.Join(d2ast.TextTransforms, ", "))
		}
		s.TextTransform.Value = value
	default:
		return fmt.Errorf("unknown style key: %s", key)
	}

	return nil
}

type ContainerLevel int

View on GitHub (pinned to 0d69dca6f5)

Solutions

Change the value to exactly `true` or `false` (also accepted: 1/0, T/F, TRUE/FALSE case-insensitively).
If the intent was to enable the border, write `style.double-border: true`.
If the value comes from user input, validate it with strconv.ParseBool before calling Set.
Check you are not setting a string like "yes"/"on"; d2 does not accept those.

Example fix

// before
style: { double-border: "yes" }
// after
style: { double-border: true }

Defensive patterns

Strategy: validation

Validate before calling

func validBool(v string) bool { _, err := strconv.ParseBool(v); return err == nil }
if !validBool(value) { value = "true" } // normalize before Set

Type guard

func isD2Bool(v string) bool {
  switch strings.ToLower(v) {
  case "true", "false", "1", "0", "t", "f": return true
  }
  return false
}

Try / catch

if err := obj.Set(ctx, "style.double-border", val); err != nil && strings.Contains(err.Error(), "double-border") {
  // fall back to a boolean default or surface a user-facing validation message
}

Prevention

Always pass literal true/false for double-border.
Validate user input with strconv.ParseBool before calling Set.
Don't confuse double-border with other style keys that accept non-boolean values.

When it happens

Trigger: Calling Set on a style map key `double-border` with a value that is not one of 1/t/T/TRUE/true/True/0/f/F/FALSE/false/False, e.g. `shape.Style.DoubleBorder.Value = "yes"` or setting it via a script/API with a non-boolean string.

Common situations: Typing `double-border: yes` or `double-border: on` in a d2 config; passing user-supplied strings from a UI into the style setter; confusing double-border (boolean) with border-radius (number).

Related errors

AI-assisted analysis of d2lang/d2@0d69dca6f5 (2026-08-31). Data as JSON: /api/errors/d3cd6a8b2acedb04. Report an issue: GitHub.