YAML Validation, Linting, and Troubleshooting

name:John

# Show a syntax issue many parsers reject.

users:
- name: Jonathan
 role: admin

# Illustrate how list nesting can break parsing.

app:
  port: 8080
  port: 9090

# Show why repeated keys are dangerous.

yamllint config.yaml

# Catch common syntax and style problems in one pass.

python - <<'PY'
import yaml, sys
with open('broken.yaml') as f:
    print(yaml.safe_load(f))
PY

# Confirm whether a parser can load a YAML document.

ruby -e 'require "yaml"; p YAML.load_file("config.yaml")'

# Use Ruby's YAML parser to validate a file.

yq -o=json '.' config.yaml | jq '.'

# Convert YAML to JSON to inspect the normalized data model.

git diff --word-diff=color config.yaml

# Use Git diff modes that make structural edits easier to inspect.