mikefarah/yq · error

filename expression returned nil

Error message

filename expression returned nil

What it means

loadString evaluates its RHS expression to obtain a filename; the evaluation succeeded but produced zero matching nodes (front() == nil). There is no filename to open — typically the filename expression selected a missing field or filtered everything out.

Source

Thrown at pkg/yqlib/operator_load.go:80

}

func loadStringOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
	log.Debugf("loadString")
	if ConfiguredSecurityPreferences.DisableFileOps {
		return Context{}, fmt.Errorf("file operations have been disabled")
	}

	var results = list.New()

	for el := context.MatchingNodes.Front(); el != nil; el = el.Next() {
		candidate := el.Value.(*CandidateNode)

		rhs, err := d.GetMatchingNodes(context.SingleReadonlyChildContext(candidate), expressionNode.RHS)
		if err != nil {
			return Context{}, err
		}
		if rhs.MatchingNodes.Front() == nil {
			return Context{}, fmt.Errorf("filename expression returned nil")
		}
		nameCandidateNode := rhs.MatchingNodes.Front().Value.(*CandidateNode)

		filename := nameCandidateNode.Value

		contentsCandidate, err := loadString(filename)
		if err != nil {
			return Context{}, fmt.Errorf("failed to load %v: %w", filename, err)
		}

		results.PushBack(contentsCandidate)

	}

	return context.ChildContext(results), nil
}

func loadOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {

View on GitHub (pinned to 8b5af0694b)

Solutions

1. Make the filename expression always yield a string, e.g. "file.yaml" as a literal
2. Check that the field holding the filename exists: .filename // "default.yaml"
3. Avoid select() filters that can return nothing on the RHS of load

When it happens

Trigger: Thrown at pkg/yqlib/operator_load.go:80 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/7abb2194c86eef91. Report an issue: GitHub.