expected "opacity" to be a number between 0.0 and 1.0

Error message

expected "opacity" to be a number between 0.0 and 1.0

What it means

The D2 style validator requires the 'opacity' style key to be a float between 0.0 and 1.0. This error is returned when the value fails ParseFloat, is NaN or Inf, or is outside [0,1]. Thrown from the style-key switch in d2graph.ApplyKey-like style application.

Source

Thrown at d2graph/d2graph.go:323

	TextTransform *Scalar `json:"textTransform,omitempty"`
}

// NoneTextTransform will return a boolean if the text should not have any
// transformation applied. This should overwrite theme specific transformations
// like `CapsLock` from the `terminal` theme.
func (s Style) NoneTextTransform() bool {
	return s.TextTransform != nil && s.TextTransform.Value == "none"
}

func (s *Style) Apply(key, value string) error {
	switch key {
	case "opacity":
		if s.Opacity == nil {
			break
		}
		f, err := strconv.ParseFloat(value, 64)
		if err != nil || math.IsNaN(f) || math.IsInf(f, 0) || f < 0 || f > 1 {
			return errors.New(`expected "opacity" to be a number between 0.0 and 1.0`)
		}
		s.Opacity.Value = value
	case "stroke":
		if s.Stroke == nil {
			break
		}
		if !color.ValidColor(value) {
			return errors.New(`expected "stroke" to be a valid named color ("orange"), a hex code ("#f0ff3a"), or a gradient ("linear-gradient(red, blue)")`)
		}
		s.Stroke.Value = value
	case "fill":
		if s.Fill == nil {
			break
		}
		if !color.ValidColor(value) {
			return errors.New(`expected "fill" to be a valid named color ("orange"), a hex code ("#f0ff3a"), or a gradient ("linear-gradient(red, blue)")`)
		}
		s.Fill.Value = value

View on GitHub (pinned to 0d69dca6f5)

Solutions

Set opacity to a decimal fraction between 0.0 and 1.0, e.g. 0.5 for 50%.
Convert percentage values by dividing by 100 (100 -> 1.0).
Fix numeric typos (commas as decimal separators, stray units).

Example fix

// before
x.style.opacity: 100
// after
x.style.opacity: 1.0

Defensive patterns

Strategy: validation

Validate before calling

f, err := strconv.ParseFloat(v, 64)
if err != nil || math.IsNaN(f) || math.IsInf(f, 0) || f < 0 || f > 1 {
    return fmt.Errorf("opacity %q must be between 0.0 and 1.0", v)
}

Type guard

func validOpacity(s string) bool { f, err := strconv.ParseFloat(s, 64); return err == nil && !math.IsNaN(f) && !math.IsInf(f, 0) && f >= 0 && f <= 1 }

Try / catch

if err := applyStyle(key, value); err != nil {
    if strings.Contains(err.Error(), "opacity") {
        // fall back to a safe default
        value = "1.0"
    }
}

Prevention

Express opacity as a fraction (0.0–1.0), never a percentage.
Pre-validate with ParseFloat plus NaN/Inf/range checks mirroring d2graph.
Clamp computed opacities to [0,1] before writing them into the graph.

When it happens

Trigger: Setting a shape's style 'opacity' (via d2graph style application with s.Opacity != nil) to a value like "1.5", "abc", "NaN", "Inf", or "-0.2".

Common situations: D2 diagram authors writing `shape.style.opacity: 100` (expecting percentage) or a typo like "0,5" in a .d2 file; programmatic graph manipulation assigning invalid opacity strings.

Related errors

AI-assisted analysis of d2lang/d2@0d69dca6f5 (2026-08-31). Data as JSON: /api/errors/8d9976ac8aad204b. Report an issue: GitHub.