mikefarah/yq · error

csv encoding only works for arrays of scalars (string/number

Error message

csv encoding only works for arrays of scalars (string/numbers/booleans), child[%v] is a %v

What it means

encodeRow, which flattens one array row into CSV columns, found a child that is not a ScalarNode (e.g. a nested map or array at child index %v). CSV rows are flat: every element of each array must be a string, number, or boolean; nested structures cannot be represented as a single CSV cell.

Source

Thrown at pkg/yqlib/encoder_csv.go:37

func (e *csvEncoder) CanHandleAliases() bool {
	return false
}

func (e *csvEncoder) PrintDocumentSeparator(_ io.Writer) error {
	return nil
}

func (e *csvEncoder) PrintLeadingContent(_ io.Writer, _ string) error {
	return nil
}

func (e *csvEncoder) encodeRow(csvWriter *csv.Writer, contents []*CandidateNode) error {
	stringValues := make([]string, len(contents))

	for i, child := range contents {

		if child.Kind != ScalarNode {
			return fmt.Errorf("csv encoding only works for arrays of scalars (string/numbers/booleans), child[%v] is a %v", i, child.Tag)
		}
		stringValues[i] = child.Value
	}
	return csvWriter.Write(stringValues)
}

func (e *csvEncoder) encodeArrays(csvWriter *csv.Writer, content []*CandidateNode) error {
	for i, child := range content {

		if child.Kind != SequenceNode {
			return fmt.Errorf("csv encoding only works for arrays of scalars (string/numbers/booleans), child[%v] is a %v", i, child.Tag)
		}
		err := e.encodeRow(csvWriter, child.Content)
		if err != nil {
			return err
		}
	}
	return nil

View on GitHub (pinned to 8b5af0694b)

Solutions

1. Flatten nested structures before encoding (e.g. using [.[] | ... ] or flatten)
2. Convert the nested value to a string with tostring
3. Use a hierarchical format (@json/@yaml) instead of @csv if nesting must be preserved

When it happens

Trigger: Thrown at pkg/yqlib/encoder_csv.go:37 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mikefarah/yq@8b5af0694b (2026-09-05). Data as JSON: /api/errors/60a11b2dcf9780b3. Report an issue: GitHub.