gohugoio/hugo · error

invalid options type: %w

Error message

invalid options type: %w

What it means

In the two-argument form of a resource transformation, the resource was valid but the first argument (the options) could not be converted to map[string]any by hmaps.ToStringMapE. Hugo wraps the underlying conversion error with %w. Options for transforms like PostCSS, Babel, ToCSS, and Fingerprint variants must be a dict/map.

Source

Thrown at tpl/internal/resourcehelpers/helpers.go:65

	if len(args) == 1 {
		r, ok := args[0].(resources.ResourceTransformer)
		if !ok {
			return nil, nil, fmt.Errorf("type %T not supported in Resource transformations", args[0])
		}
		return r, nil, nil
	}

	r, ok := args[1].(resources.ResourceTransformer)
	if !ok {
		if _, ok := args[1].(map[string]any); !ok {
			return nil, nil, fmt.Errorf("no Resource provided in transformation")
		}
		return nil, nil, fmt.Errorf("type %T not supported in Resource transformations", args[0])
	}

	m, err := hmaps.ToStringMapE(args[0])
	if err != nil {
		return nil, nil, fmt.Errorf("invalid options type: %w", err)
	}

	return r, m, nil
}

View on GitHub ↗ (pinned to 8a468df065)

Solutions

1. Wrap options in a dict: `{{ $r | resources.PostCSS (dict "config" "config.js") }}`.
2. Check the specific transform's docs for its option keys (e.g. toCSS: targetPath, transpiler, vars).
3. If building options dynamically, verify with `printf "%T"` that it is a map before passing.

Example fix

<!-- before -->
{{ $css := $scss | toCSS "main.css" }}
<!-- after -->
{{ $css := $scss | toCSS (dict "targetPath" "main.css") }}

{{ $opts := dict "targetPath" "css/main.css" "outputStyle" "compressed" }}
{{ $css := $scss | css.Sass $opts }}

{{/* options must be a map/dict, not a string or slice */}}

When it happens

Trigger: `{{ $r | resources.PostCSS "config.js" }}` or any transform given a string/slice/number as options instead of a dict, so ToStringMapE fails on the non-map type.

Common situations: Passing a config file path or preset name as a bare string where a dict is required; passing `slice` instead of `dict`; options built in a partial arriving as the wrong type.

Related errors

• no Resource provided in transformation
• type %T not supported in Resource transformations
• no Key set in Resource
• resources.PostProcess cannot be used in a deferred template
• failed to decode options: %w

AI-assisted analysis of gohugoio/hugo@8a468df065 (2026-07-31). Data as JSON: /data/errors/c63e920577bb4a84.json. Report an issue: GitHub ↗.