GoogleContainerTools/skaffold · critical

unable to parse YAML: %w

Error message

unable to parse YAML: %w

What it means

removeYamlAnchors parses the config YAML document-by-document to strip top-level keys starting with a dot. If any document fails to decode into a generic map, this wrapped error is returned from ParseConfig.

Source

Thrown at pkg/skaffold/schema/versions.go:298

	return factories, nil
}

// removeYamlAnchors removes all top-level keys starting with `.` from the input stream so they can be used as YAML anchors
func removeYamlAnchors(buf []byte) ([]byte, error) {
	in := bytes.NewReader(buf)
	var out bytes.Buffer

	decoder := yaml.NewDecoder(in)
	decoder.KnownFields(true)
	encoder := yaml.NewEncoder(&out)
	for {
		parsed := make(map[string]interface{})
		err := decoder.Decode(parsed)
		if err == io.EOF {
			break
		}
		if err != nil {
			return nil, fmt.Errorf("unable to parse YAML: %w", err)
		}
		for field := range parsed {
			if strings.HasPrefix(field, ".") {
				delete(parsed, field)
			}
		}
		err = encoder.Encode(parsed)
		if err != nil {
			return nil, err
		}
	}
	err := encoder.Close()
	if err != nil {
		return nil, err
	}
	return out.Bytes(), nil
}

View on GitHub (pinned to a1189de023)

Solutions

1. Ensure every YAML document in the file is a mapping (key: value form), not a bare scalar or list
2. Run yamllint to locate syntax errors and fix them
3. Check the wrapped cause (%w) for the exact failing document/line
4. Remove stray '---' separators or empty/broken trailing documents

Example fix

# before (non-mapping document)
apiVersion: skaffold/v4beta7
kind: Config
---
just a scalar
# after
apiVersion: skaffold/v4beta7
kind: Config

docs := strings.Split(string(data), "\n---")
for _, d := range docs {
	var m map[string]interface{}
	if err := yaml.Unmarshal([]byte(d), &m); err != nil || m == nil {
		return fmt.Errorf("YAML document is not a valid mapping: %w", err)
	}
}

_, err := schema.ParseConfig(cfgPath)
if err != nil {
	if strings.Contains(err.Error(), "unable to parse YAML") {
		// run yamllint and show the wrapped cause to the user
	}
	return err
}

When it happens

Trigger: Calling ParseConfig on a YAML file where a document is syntactically invalid or is not decodable as map[string]interface{} (e.g. a bare scalar or sequence document mixed into the file).

Common situations: A skaffold.yaml containing malformed segments; multi-document files where one document is not a mapping (e.g. a stray '---' followed by a scalar); syntax errors like unclosed quotes.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• unable to re-marshal YAML without dotted keys: %w
• parsing api version: %w
• read skaffold config: %w
• `apply` requires at least one manifest argument
• `exec` requires exactly one action to execute

AI-assisted analysis of GoogleContainerTools/skaffold@a1189de023 (2026-09-05). Data as JSON: /api/errors/3a745915f84e700d. Report an issue: GitHub.