abiosoft/colima · error

unexpected error during yaml decode: doc has multiple childr

Error message

unexpected error during yaml decode: doc has multiple children of len %d

What it means

encodeYAML (util/yamlutil/yaml.go:52) requires the unmarshaled document node to have exactly one child — the root mapping. A yaml.Node document with multiple Content children means the source YAML contained multiple documents separated by '---'. yaml.v3's Unmarshal into a single Node tolerates multi-document input, so colima defends here by rejecting it before traversal; the embedded default is a single document, so this fires only when that invariant is broken.

Source

Thrown at util/yamlutil/yaml.go:52

	}

	return nil
}

func encodeYAML(conf config.Config) ([]byte, error) {
	var doc yaml.Node

	f, err := embedded.Read("defaults/colima.yaml")
	if err != nil {
		return nil, fmt.Errorf("error reading config file: %w", err)
	}

	if err := yaml.Unmarshal(f, &doc); err != nil {
		return nil, fmt.Errorf("embedded default config is invalid yaml: %w", err)
	}

	if l := len(doc.Content); l != 1 {
		return nil, fmt.Errorf("unexpected error during yaml decode: doc has multiple children of len %d", l)
	}
	root := doc.Content[0]

	// get all nodes
	nodeVals := map[string]*yaml.Node{}
	if err := traverseNode("", root, nodeVals); err != nil {
		return nil, fmt.Errorf("error traversing yaml node: %w", err)
	}

	// get all node values
	structVals := map[string]any{}
	traverseConfig("", conf, structVals)

	// apply values to nodes
	for key, node := range nodeVals {
		val := structVals[key]

		// top level, ignore. except known maps.

View on GitHub (pinned to c3a5f9184d)

Solutions

1. Remove '---' separators from embedded/defaults/colima.yaml so it is exactly one document
2. If multiple documents are truly needed, split the file and read only the first document explicitly
3. Add a lint step rejecting multi-document content in the embedded defaults
4. Revert to the stock embedded file and layer changes through colima's config instead

Example fix

# embedded/defaults/colima.yaml (before) — two documents
vm:
  cpu: 4
---
mounts: []

# after — single document
vm:
  cpu: 4
mounts: []

// reject multi-document YAML before it reaches encodeYAML
func isSingleDocument(b []byte) bool {
    d := yaml.NewDecoder(bytes.NewReader(b))
    var v any
    if err := d.Decode(&v); err != nil { return false }
    return d.Decode(&v) == io.EOF
}

if err := util.Save(cfg, file); err != nil {
    if strings.Contains(err.Error(), "multiple children") {
        // embedded template gained '---' separators: reinstall or fix the asset
        return fmt.Errorf("colima defaults corrupted (multi-doc) — reinstall: %w", err)
    }
    return err
}

When it happens

Trigger: An embedded/defaults/colima.yaml that gained a '---' document separator (e.g. concatenated files), producing doc.Content of length 2+.

Common situations: Fork merges that concatenate snippets onto the defaults file; tooling that appends generated YAML with a leading ---; copy-paste of multi-document Kubernetes-style YAML into the defaults template.

Related errors

• embedded default config is invalid yaml: %w
• error traversing yaml node: %w
• error reading config file: %w
• unexpected error during yaml node traversal: %w
• unexpected error during yaml node traversal: doc has multipl

AI-assisted analysis of abiosoft/colima@c3a5f9184d (2026-08-15). Data as JSON: /api/errors/5a5343cb154d070b. Report an issue: GitHub.