mikefarah/yq · error

unsupported node kind for TOML: %v

Error message

unsupported node kind for TOML: %v

What it means

Inside encodeTopLevelEntry, the switch over node Kind handles scalar, sequence (incl. array-of-tables), and mapping (incl. inline tables); any other Kind falls through to 'unsupported node kind for TOML: %v'. This guards against kinds TOML cannot represent at a top-level entry position.

Source

Thrown at pkg/yqlib/encoder_toml.go:213

					return err
				}
			}
			return nil
		}
		// Regular array attribute
		return te.writeArrayAttribute(w, path[len(path)-1], node)
	case MappingNode:
		// Use inline table syntax only for nodes explicitly marked as TOML inline tables.
		// YAML flow-style mappings are not treated as inline tables; the FlowStyle attribute
		// is a YAML-specific rendering hint and should not affect TOML output. This ensures
		// that auto-detected JSON input (parsed as YAML flow style) produces readable table
		// sections, consistent with explicitly parsed JSON input.
		if node.EncodeHint == EncodeHintInline {
			return te.writeInlineTableAttribute(w, path[len(path)-1], node)
		}
		return te.encodeSeparateMapping(w, path, node)
	default:
		return fmt.Errorf("unsupported node kind for TOML: %v", node.Kind)
	}
}

func isTomlArrayOfTables(seq *CandidateNode) bool {
	if len(seq.Content) == 0 {
		return false
	}
	for _, it := range seq.Content {
		if it.Kind != MappingNode || it.EncodeHint == EncodeHintInline {
			return false
		}
	}
	return true
}

func isTomlAttribute(node *CandidateNode) bool {
	if node.Kind == ScalarNode {
		return true

View on GitHub (pinned to 8b5af0694b)

Solutions

1. Resolve aliases before encoding: `yq -o toml '(.[] | select(is("alias"))) |= eval'` or avoid anchors in the source.
2. Flatten/simplify the expression so values are plain scalars, maps, or sequences.
3. Preview with `-o json` to identify the offending node and normalize it (e.g. with `.|= .` dereferencing or rebuilding).
4. Upgrade yq — alias handling in the TOML encoder has improved over releases.

Example fix

# before
yq -o toml '.' doc.yaml   # value is an alias node -> unsupported kind

# after
yq -o toml '(.. | select(kind == "alias")) |= eval' doc.yaml

yq '[.. | kind] | unique' file.yaml   # look for 'alias' or unexpected kinds before -o toml

hasAlias() { yq -e '[.. | kind] | any(. == "alias")' "$1" > /dev/null; }

yq -o toml '.' doc.yaml 2>/dev/null || yq -o toml '(.. | select(kind == "alias")) |= eval' doc.yaml

When it happens

Trigger: A root mapping whose value node has a non-scalar/seq/map Kind (typically an unresolved AliasNode or document/fragment node) is encoded with `-o toml`, falling into the default branch at encoder_toml.go:213.

Common situations: YAML anchors/aliases not resolved before TOML encoding; synthetic nodes built by expressions that keep document kinds; hand-built CandidateNodes via the library API.

Related errors

• TOML encoder expects a mapping at the root level
• INI encoder supports only MappingNode at the root level, got
• unsupported node %v
• unsupported node %v
• cannot encode TOML entry with empty path

AI-assisted analysis of mikefarah/yq@8b5af0694b (2026-09-05). Data as JSON: /api/errors/653cd5f891e9314e. Report an issue: GitHub.