レッスン 4
Common YAML Mistakes 日本語ガイド
日本語の yaml common yaml mistakes ガイド: Indentation, tabs, typing, and paste errors that break configs.
このコンテンツはまだ日本語で用意されていません。ローカライズが完了するまで English 版を表示しています。
YAML failures are rarely mysterious once you know the usual suspects.
Tabs vs spaces
Many style guides forbid tabs for indentation. Mixing tabs and spaces looks aligned in some editors but breaks parsers. Configure your editor to insert spaces for YAML.
Off-by-one indent levels
Adding a key one space too far left attaches it to the wrong parent. In Kubernetes, that can move containers out of spec silently in your head—but not to the parser.
Unquoted special scalars
YAML interprets values like yes, no, on, off, and 12345 with typing rules. When you mean a string, quote it:
version: "01.10"
enabled: "yes"
Broken flow collections
Starting [ or { sequences without matching closers produces errors deep in the file. CI generators sometimes emit half-valid flow YAML—validate after paste.
Multiple documents in one paste
Files separated by --- are valid multi-document YAML, but some tools expect a single document. Merging two manifests without understanding document boundaries causes confusing errors.
Double conversion
JSON → YAML → manual edit → JSON can introduce duplicate keys or changed types if intermediate tools reorder or normalize values. Diff after every conversion step.