How to Do Block Comments in YAML

YAML (YAML Ain’t Markup Language) is a popular data serialization language used for configuration files, data exchange, and more. It’s known for its human-readable format, which makes it easy to work with. However, like many other programming and data formats, YAML supports comments that help explain the data, document configurations, or temporarily disable sections of code.

In this article, we’ll look at how to write block comments in YAML and discuss some best practices.

Understanding Comments in YAML

In YAML, comments are lines that are ignored by the YAML parser. They are typically used to add explanations, clarify data structure, or provide context for developers. Comments in YAML are initiated with the # symbol.

Inline Comments

Inline comments are written on the same line as a value, following the # symbol.

Block Comments

Block comments, on the other hand, are used when you need to comment out multiple lines or provide a more detailed explanation over several lines. YAML does not have a specific syntax for block comments like other languages (e.g., /* ... */ in C-like languages), but you can achieve block comments by starting each line with the # symbol.

How to Write Block Comments in YAML

In YAML, to create a block comment, simply place the # symbol at the beginning of each line you want to comment out. There’s no official block comment syntax, but it’s easy to create one manually by applying the comment symbol to multiple lines.

Example of Block Comments

In the above example, the block comment spans several lines. Each line starts with the # symbol, and the parser will ignore these lines.

Commenting Out a Section of Configuration

When you need to comment out an entire section of a configuration, you can use block comments to make the section inactive temporarily.

Example:

In this example, the entire database section is commented out. The YAML parser will ignore this configuration when reading the file.

Best Practices for Writing Block Comments in YAML

1. Clarity: Use block comments to explain the structure or purpose of complex sections of your YAML file. Always make sure the comments are clear and easy to understand.
2. Consistency: Start each line of a block comment with the # symbol. Avoid mixing inline comments and block comments in the same section to maintain readability.
3. Documentation: Use block comments to document the configuration parameters, possible values, or any assumptions or special handling required for certain settings. This is especially helpful for users who may be unfamiliar with the YAML file or its structure.
4. Temporarily Disable Sections: Block comments are useful for commenting out large sections of YAML temporarily, allowing you to disable them without deleting the code.
5. Avoid Overuse: While comments are helpful, too many comments can clutter the YAML file. Be selective and add comments where necessary to enhance clarity.

Alternative Methods for Multiline Comments

While YAML itself doesn’t support a dedicated block comment syntax, other methods can be used to manage multiline comments more cleanly:

• Indentation for Nested Comments: When working with complex structures, some developers prefer indenting block comments for clarity, making the comment’s relation to the content more explicit.
  yaml

  # This section contains the main server configuration
#
# It includes host, port, and protocol settings
server:
host: localhost
port: 8080

• Using External Commenting Tools: If your YAML file is part of a larger project, it might be helpful to use version control tools or IDE features (such as multi-line comment blocks) that help with commenting out sections.

Conclusion

YAML is a straightforward and human-readable data format that makes commenting easy, but there’s no built-in block comment syntax. Instead, block comments can be created by placing the # symbol at the start of each line you want to comment out. This allows you to provide detailed explanations, disable sections of the configuration, or improve readability.

By following best practices for clarity and consistency, you can effectively use block comments in YAML to maintain clean, well-documented configuration files.