d2lang/d2 · error

invalid gradient syntax

Error message

invalid gradient syntax

What it means

lib/color.ParseGradient parses CSS gradient strings like 'linear-gradient(...)' or 'radial-gradient(...)'. If the trimmed input does not match the required outer syntax — the gradient function name with parentheses wrapping parameters — it returns 'invalid gradient syntax'. The parser is strict: it accepts only these two gradient types with a balanced parenthesized parameter list.

Source

Thrown at lib/color/gradient.go:32

type Gradient struct {
	Type       string
	Direction  string
	ColorStops []ColorStop
	ID         string
}

type ColorStop struct {
	Color    string
	Position string
}

func ParseGradient(cssGradient string) (Gradient, error) {
	cssGradient = strings.TrimSpace(cssGradient)

	re := regexp.MustCompile(`^(linear-gradient|radial-gradient)\((.*)\)$`)
	matches := re.FindStringSubmatch(cssGradient)
	if matches == nil {
		return Gradient{}, errors.New("invalid gradient syntax")
	}

	gradientType := matches[1]
	params := matches[2]

	gradient := Gradient{
		Type: strings.TrimSuffix(gradientType, "-gradient"),
	}

	paramList := splitParams(params)

	if len(paramList) == 0 {
		return Gradient{}, errors.New("no parameters in gradient")
	}

	firstParam := strings.TrimSpace(paramList[0])

	if gradient.Type == "linear" && (strings.HasSuffix(firstParam, "deg") || strings.HasPrefix(firstParam, "to ")) {

View on GitHub (pinned to 0d69dca6f5)

Solutions

1. Use only linear-gradient(...) or radial-gradient(...) syntax as the color value
2. Trim whitespace and remove any trailing punctuation (e.g. ';') from the value before parsing
3. Validate the string with lib/color.ValidColor (which uses ParseGradient) before assigning it to a style

Example fix

// before
grad, err := color.ParseGradient("conic-gradient(from 0deg, red, blue)") // invalid syntax
// after
grad, err := color.ParseGradient("linear-gradient(to right, red, blue)")

re := regexp.MustCompile(`^(linear-gradient|radial-gradient)\(.*\)$`)
if !re.MatchString(strings.TrimSpace(cssGradient)) {
    return errors.New("not a supported linear/radial gradient")
}

func isSupportedGradient(s string) bool {
    s = strings.TrimSpace(s)
    return regexp.MustCompile(`^(linear-gradient|radial-gradient)\(.*\)$`).MatchString(s)
}

grad, err := color.ParseGradient(input)
if err != nil && strings.Contains(err.Error(), "invalid gradient syntax") {
    // fall back to a solid color
}

When it happens

Trigger: Calling ParseGradient (directly or indirectly through ValidColor or color parsing of a style value) with a string that is not of the form 'linear-gradient(...)' or 'radial-gradient(...)', e.g. 'conic-gradient(red, blue)', 'linear-gradient(red, blue' (unbalanced parens), or extra text outside the parens.

Common situations: D2 style values using unsupported gradient types like conic-gradient; typos in the gradient function name; trailing semicolons or whitespace/newline artifacts; copying gradients from other CSS contexts that include vendor prefixes or surrounding declarations.

Related errors

• no parameters in gradient
• no color stops in gradient
• invalid color "%s"
• cannot parse hex color %v
• failed to unmarshal Range from %q: missing End field

AI-assisted analysis of d2lang/d2@0d69dca6f5 (2026-08-31). Data as JSON: /api/errors/28de4e29cfccdc36. Report an issue: GitHub.