YAML Lint

YAML lint written in Java.
Its main purpose is to provide an API and scripts to analyze YAML documents.
The YAML documents are syntactically checked as well as against rules. To get the list of rules, please refer to the classes
of the com.github.sbaudoin.yamllint.rules package. Among
other, we have a rule to check the presence of the start and end YAML document marker, the correct and consistent indentation, etc.

API usage

Maven dependency:

<dependency>
    <groupId>com.github.sbaudoin</groupId>
    <artifactId>yamllint</artifactId>
    <version>1.6.1</version>
</dependency>

For use, please refer to the JavaDoc.

The class that will mostly interest you is com.github.sbaudoin.yamllint.Linter: it contains static methods
that can be used to analyze a YAML string or a file.

3 errors levels have been defined: info, warning and error.

The linter can return only one syntax error per file (once a syntax error has been met we cannot expect a lot from the rest
of the file with respect to the syntax). It is returned apart, not as part of the so-called "cosmetic errors", that represent
all other errors checked with specific rules.

Configuration

YAML lint uses rules to check the YAML files. These rules have default
settings that can changed or overridden with, whether an instance of com.github.sbaudoin.yamllint.YamlLintConfig or a YAML
configuration file if using the batch tool (see below). The expected format for this YAML configuration file is as follows:

---
yaml-files:
  - '.*\.yaml'
  - '.*\.yml'

ignore: pathspecs

rules:
  <rule name>: enable|disable
    level: info|warning|error
    ignore: pathspecs
    rule_conf_param1: value
    rule_conf_param2: value
    ...
  ...

Some details:

• The yaml-files block is optional and allows you to specify a list of regexp file name patterns used to identify YAML files.
  The default configuration is to take only the .yml and .yaml files into account.

• The ignore parameter is also optional and allows you do the contrary, i.e. specify regexp patterns to be used to
  ignore files. It can be defined globally or per rule. Be aware that it is a string, not a list, that contains an expression
  per line:

  ignore: |
    .*\.txt$
    foo.bar
  

• The rule level is also optional (the default rule level is "error").

• See the default configuration to get the default rules' parameter values.

Batch usage

Get the .zip or .tar.gz distribution archive, unpack and execute the script corresponding to your platform in the bin directory:

bin/yamllint [options] files/directories

or for Windows:

bin\yamllint [options] files/directories

or even like this to lint from the standard input:

a command | bin/yamllint [options]

Warning! The Unix version requires Bash. There is no guaranty that the script will work with other Shell interpreters.

Use the --help (or -h) option to get help with the complete list of options and values.

By default, if the terminal supports it, the output is colorized and has the following output format:

file.yml
  line:column       level  message  (ruleId)
  ...

You can force color with the -f colored format; you can force the non-colorized output with -f standard.

You can specify the -f parsable on the command line to get a parsable output as follows:

<file path>:<line>:<column>:<ruleId>:<level>:<message>

The -f github format also provides a parsable output as follows:

::<level> file=<file path>,line=<line>,col=<col>::<ruleId><message>

The YAML lint configuration file can be passed in different ways:

• Use the -d option to specify a YAML configuration directly on the command line or specify the "relaxed" configuration;
• Use the -c option to specify a path to a configuration file;
• If -c is not provided, yamllint will look for a configuration file in the following locations (by order of preference):
  • .yamllint, .yamllint.yaml or .yamllint.yml in the current working directory
  • the file referenced by YAMLLINT_CONFIG_FILE environment variable if set
  • $XDG_CONFIG_HOME/yamllint/config if the XDG_CONFIG_HOME environment variable is set
  • ~/.config/yamllint/config if this file exists
• Finally if no config file is found, the default configuration is applied.

As a reminder, the default configuration can be found here and the relaxed
version here.