gohugoio/hugo · error

unmarshal takes 1 or 2 arguments

Error message

unmarshal takes 1 or 2 arguments

What it means

Thrown by transform.Unmarshal when the argument count is not 1 or 2 (tpl/transform/unmarshal.go:39-40). Unmarshal accepts either data alone, or an options map plus data; zero args or three-plus are rejected.

Solutions

1. Provide exactly one (data) or two (options map, data) arguments.
2. Combine options into a single map: {{ transform.Unmarshal (dict "delimiter" ",") .CSV }}.
3. Ensure a value is piped or passed: {{ "..." | transform.Unmarshal }}.

Example fix

// before
{{ transform.Unmarshal .Opts .Data .Extra }}
// after
{{ transform.Unmarshal (dict "delimiter" ",") .CSV }}

{{ transform.Unmarshal (dict "delimiter" ",") .CSV }}

When it happens

Trigger: Calling {{ transform.Unmarshal }} with no args, or {{ transform.Unmarshal .Opts .Data .Extra }} with three.

Common situations: Forgetting to pass the data; piping nothing; refactoring and leaving extra args; assuming options can be split across multiple positional args.

Related errors

• first argument must be a map
• must provide at least one argument
• transform.Highlight: expects at most 3 arguments
• failed to detect target data serialization format
• invalid arguments supplied to `time`

AI-assisted analysis of gohugoio/hugo@52c9bd7908 (2026-08-09). Data as JSON: /api/errors/3dfd87e8dac1bd4b. Report an issue: GitHub.

Appendix: source

Thrown at tpl/transform/unmarshal.go:40

	"github.com/gohugoio/hugo/resources"
	"github.com/gohugoio/hugo/resources/resource"

	"github.com/gohugoio/hugo/common/hashing"
	"github.com/gohugoio/hugo/common/types"

	"github.com/mitchellh/mapstructure"

	"github.com/gohugoio/hugo/parser/metadecoders"

	"github.com/spf13/cast"
)

// Unmarshal unmarshals the data given, which can be either a string, json.RawMessage
// or a Resource. Supported formats are JSON, TOML, YAML, and CSV.
// You can optionally provide an options map as the first argument.
func (ns *Namespace) Unmarshal(args ...any) (any, error) {
	if len(args) < 1 || len(args) > 2 {
		return nil, errors.New("unmarshal takes 1 or 2 arguments")
	}

	var data any
	decoder := metadecoders.Default

	if len(args) == 1 {
		data = args[0]
	} else {
		m, ok := args[0].(map[string]any)
		if !ok {
			return nil, errors.New("first argument must be a map")
		}

		var err error

		data = args[1]
		decoder, err = decodeDecoder(m)
		if err != nil {

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