Provided by: yamllint_1.29.0-1_all 
NAME
yamllint - Linter for YAML files
A linter for YAML files.
yamllint does not only check for syntax validity, but for weirdnesses like key repetition
and cosmetic problems such as lines length, trailing spaces, indentation, etc.
SCREENSHOT
[image: yamllint screenshot] [image]
NOTE:
The default output format is inspired by eslint, a great linting tool for Javascript.
TABLE OF CONTENTS
Quickstart
Running yamllint
Basic usage:
yamllint file.yml other-file.yaml
You can also lint all YAML files in a whole directory:
yamllint .
Or lint a YAML stream from standard input:
echo -e 'this: is\nvalid: YAML' | yamllint -
The output will look like (colors are not displayed here):
file.yml
1:4 error trailing spaces (trailing-spaces)
4:4 error wrong indentation: expected 4 but found 3 (indentation)
5:4 error duplication of key "id-00042" in mapping (key-duplicates)
6:6 warning comment not indented like content (comments-indentation)
12:6 error too many spaces after hyphen (hyphens)
15:12 error too many spaces before comma (commas)
other-file.yaml
1:1 warning missing document start "---" (document-start)
6:81 error line too long (87 > 80 characters) (line-length)
10:1 error too many blank lines (4 > 2) (empty-lines)
11:4 error too many spaces inside braces (braces)
By default, the output of yamllint is colored when run from a terminal, and pure text in
other cases. Add the -f standard arguments to force non-colored output. Use the -f colored
arguments to force colored output.
Add the -f parsable arguments if you need an output format parsable by a machine (for
instance for syntax highlighting in text editors). The output will then look like:
file.yml:6:2: [warning] missing starting space in comment (comments)
file.yml:57:1: [error] trailing spaces (trailing-spaces)
file.yml:60:3: [error] wrong indentation: expected 4 but found 2 (indentation)
If you have a custom linting configuration file (see how to configure yamllint), it can be
passed to yamllint using the -c option:
yamllint -c ~/myconfig file.yaml
NOTE:
If you have a .yamllint file in your working directory, it will be automatically loaded
as configuration by yamllint.
Configuration
yamllint uses a set of rules to check source files for problems. Each rule is independent
from the others, and can be enabled, disabled or tweaked. All these settings can be
gathered in a configuration file.
To use a custom configuration file, use the -c option:
yamllint -c /path/to/myconfig file-to-lint.yaml
If -c is not provided, yamllint will look for a configuration file in the following
locations (by order of preference):
• a file named .yamllint, .yamllint.yaml, or .yamllint.yml in the current working
directory
• a filename referenced by $YAMLLINT_CONFIG_FILE, if set
• a file named $XDG_CONFIG_HOME/yamllint/config or ~/.config/yamllint/config, if present
Finally if no config file is found, the default configuration is applied.
Default configuration
Unless told otherwise, yamllint uses its default configuration:
---
yaml-files:
- '*.yaml'
- '*.yml'
- '.yamllint'
rules:
braces: enable
brackets: enable
colons: enable
commas: enable
comments:
level: warning
comments-indentation:
level: warning
document-end: disable
document-start:
level: warning
empty-lines: enable
empty-values: disable
float-values: disable
hyphens: enable
indentation: enable
key-duplicates: enable
key-ordering: disable
line-length: enable
new-line-at-end-of-file: enable
new-lines: enable
octal-values: disable
quoted-strings: disable
trailing-spaces: enable
truthy:
level: warning
Details on rules can be found on the rules page.
There is another pre-defined configuration named relaxed. As its name suggests, it is more
tolerant:
---
extends: default
rules:
braces:
level: warning
max-spaces-inside: 1
brackets:
level: warning
max-spaces-inside: 1
colons:
level: warning
commas:
level: warning
comments: disable
comments-indentation: disable
document-start: disable
empty-lines:
level: warning
hyphens:
level: warning
indentation:
level: warning
indent-sequences: consistent
line-length:
level: warning
allow-non-breakable-inline-mappings: true
truthy: disable
It can be chosen using:
yamllint -d relaxed file.yml
Extending the default configuration
When writing a custom configuration file, you don't need to redefine every rule. Just
extend the default configuration (or any already-existing configuration file).
For instance, if you just want to disable the comments-indentation rule, your file could
look like this:
# This is my first, very own configuration file for yamllint!
# It extends the default conf by adjusting some options.
extends: default
rules:
comments-indentation: disable # don't bother me with this rule
Similarly, if you want to set the line-length rule as a warning and be less strict on
block sequences indentation:
extends: default
rules:
# 80 chars should be enough, but don't fail if a line is longer
line-length:
max: 80
level: warning
# accept both key:
# - item
#
# and key:
# - item
indentation:
indent-sequences: whatever
Custom configuration without a config file
It is possible -- although not recommended -- to pass custom configuration options to
yamllint with the -d (short for --config-data) option.
Its content can either be the name of a pre-defined conf (example: default or relaxed) or
a serialized YAML object describing the configuration.
For instance:
yamllint -d "{extends: relaxed, rules: {line-length: {max: 120}}}" file.yaml
Errors and warnings
Problems detected by yamllint can be raised either as errors or as warnings. The CLI will
output them (with different colors when using the colored output format, or auto when run
from a terminal).
By default the script will exit with a return code 1 only when there is one or more
error(s).
However if strict mode is enabled with the -s (or --strict) option, the return code will
be:
• 0 if no errors or warnings occur
• 1 if one or more errors occur
• 2 if no errors occur, but one or more warnings occur
If the script is invoked with the --no-warnings option, it won't output warning level
problems, only error level ones.
YAML files extensions
To configure what yamllint should consider as YAML files when listing directories, set
yaml-files configuration option. The default is:
yaml-files:
- '*.yaml'
- '*.yml'
- '.yamllint'
The same rules as for ignoring paths apply (.gitignore-style path pattern, see below).
If you need to know the exact list of files that yamllint would process, without really
linting them, you can use --list-files:
yamllint --list-files .
Ignoring paths
It is possible to exclude specific files or directories, so that the linter doesn't
process them. They can be provided either as a list of paths, or as a bulk string.
You can either totally ignore files (they won't be looked at):
extends: default
ignore: |
/this/specific/file.yaml
all/this/directory/
*.template.yaml
# or:
ignore:
- /this/specific/file.yaml
- all/this/directory/
- '*.template.yaml'
or ignore paths only for specific rules:
extends: default
rules:
trailing-spaces:
ignore: |
/this-file-has-trailing-spaces-but-it-is-OK.yaml
/generated/*.yaml
# or:
rules:
trailing-spaces:
ignore:
- /this-file-has-trailing-spaces-but-it-is-OK.yaml
- /generated/*.yaml
Note that this .gitignore-style path pattern allows complex path exclusion/inclusion, see
the pathspec README file for more details. Here is a more complex example:
# For all rules
ignore: |
*.dont-lint-me.yaml
/bin/
!/bin/*.lint-me-anyway.yaml
extends: default
rules:
key-duplicates:
ignore: |
generated
*.template.yaml
trailing-spaces:
ignore: |
*.ignore-trailing-spaces.yaml
ascii-art/*
You can also use the .gitignore file (or any list of files) through:
ignore-from-file: .gitignore
or:
ignore-from-file: [.gitignore, .yamlignore]
NOTE:
However, this is mutually exclusive with the ignore key.
If you need to know the exact list of files that yamllint would process, without really
linting them, you can use --list-files:
yamllint --list-files .
Setting the locale
It is possible to set the locale option globally. This is passed to Python's
locale.setlocale, so an empty string "" will use the system default locale, while e.g.
"en_US.UTF-8" will use that.
Currently this only affects the key-ordering rule. The default will order by Unicode code
point number, while locales will sort case and accents properly as well.
extends: default
locale: en_US.UTF-8
Rules
When linting a document with yamllint, a series of rules (such as line-length,
trailing-spaces, etc.) are checked against.
A configuration file can be used to enable or disable these rules, to set their level
(error or warning), but also to tweak their options.
This page describes the rules and their options.
List of rules
• braces
• brackets
• colons
• commas
• comments
• comments-indentation
• document-end
• document-start
• empty-lines
• empty-values
• float-values
• hyphens
• indentation
• key-duplicates
• key-ordering
• line-length
• new-line-at-end-of-file
• new-lines
• octal-values
• quoted-strings
• trailing-spaces
• truthy
braces
Use this rule to control the use of flow mappings or number of spaces inside braces ({ and
}).
Options
• forbid is used to forbid the use of flow mappings which are denoted by surrounding
braces ({ and }). Use true to forbid the use of flow mappings completely. Use non-empty
to forbid the use of all flow mappings except for empty ones.
• min-spaces-inside defines the minimal number of spaces required inside braces.
• max-spaces-inside defines the maximal number of spaces allowed inside braces.
• min-spaces-inside-empty defines the minimal number of spaces required inside empty
braces.
• max-spaces-inside-empty defines the maximal number of spaces allowed inside empty
braces.
Default values (when enabled)
rules:
braces:
forbid: false
min-spaces-inside: 0
max-spaces-inside: 0
min-spaces-inside-empty: -1
max-spaces-inside-empty: -1
Examples
1. With braces: {forbid: true}
the following code snippet would PASS:
object:
key1: 4
key2: 8
the following code snippet would FAIL:
object: { key1: 4, key2: 8 }
2. With braces: {forbid: non-empty}
the following code snippet would PASS:
object: {}
the following code snippet would FAIL:
object: { key1: 4, key2: 8 }
3. With braces: {min-spaces-inside: 0, max-spaces-inside: 0}
the following code snippet would PASS:
object: {key1: 4, key2: 8}
the following code snippet would FAIL:
object: { key1: 4, key2: 8 }
4. With braces: {min-spaces-inside: 1, max-spaces-inside: 3}
the following code snippet would PASS:
object: { key1: 4, key2: 8 }
the following code snippet would PASS:
object: { key1: 4, key2: 8 }
the following code snippet would FAIL:
object: { key1: 4, key2: 8 }
the following code snippet would FAIL:
object: {key1: 4, key2: 8 }
5. With braces: {min-spaces-inside-empty: 0, max-spaces-inside-empty: 0}
the following code snippet would PASS:
object: {}
the following code snippet would FAIL:
object: { }
6. With braces: {min-spaces-inside-empty: 1, max-spaces-inside-empty: -1}
the following code snippet would PASS:
object: { }
the following code snippet would FAIL:
object: {}
brackets
Use this rule to control the use of flow sequences or the number of spaces inside brackets
([ and ]).
Options
• forbid is used to forbid the use of flow sequences which are denoted by surrounding
brackets ([ and ]). Use true to forbid the use of flow sequences completely. Use
non-empty to forbid the use of all flow sequences except for empty ones.
• min-spaces-inside defines the minimal number of spaces required inside brackets.
• max-spaces-inside defines the maximal number of spaces allowed inside brackets.
• min-spaces-inside-empty defines the minimal number of spaces required inside empty
brackets.
• max-spaces-inside-empty defines the maximal number of spaces allowed inside empty
brackets.
Default values (when enabled)
rules:
brackets:
forbid: false
min-spaces-inside: 0
max-spaces-inside: 0
min-spaces-inside-empty: -1
max-spaces-inside-empty: -1
Examples
1. With brackets: {forbid: true}
the following code snippet would PASS:
object:
- 1
- 2
- abc
the following code snippet would FAIL:
object: [ 1, 2, abc ]
2. With brackets: {forbid: non-empty}
the following code snippet would PASS:
object: []
the following code snippet would FAIL:
object: [ 1, 2, abc ]
3. With brackets: {min-spaces-inside: 0, max-spaces-inside: 0}
the following code snippet would PASS:
object: [1, 2, abc]
the following code snippet would FAIL:
object: [ 1, 2, abc ]
4. With brackets: {min-spaces-inside: 1, max-spaces-inside: 3}
the following code snippet would PASS:
object: [ 1, 2, abc ]
the following code snippet would PASS:
object: [ 1, 2, abc ]
the following code snippet would FAIL:
object: [ 1, 2, abc ]
the following code snippet would FAIL:
object: [1, 2, abc ]
5. With brackets: {min-spaces-inside-empty: 0, max-spaces-inside-empty: 0}
the following code snippet would PASS:
object: []
the following code snippet would FAIL:
object: [ ]
6. With brackets: {min-spaces-inside-empty: 1, max-spaces-inside-empty: -1}
the following code snippet would PASS:
object: [ ]
the following code snippet would FAIL:
object: []
colons
Use this rule to control the number of spaces before and after colons (:).
Options
• max-spaces-before defines the maximal number of spaces allowed before colons (use -1 to
disable).
• max-spaces-after defines the maximal number of spaces allowed after colons (use -1 to
disable).
Default values (when enabled)
rules:
colons:
max-spaces-before: 0
max-spaces-after: 1
Examples
1. With colons: {max-spaces-before: 0, max-spaces-after: 1}
the following code snippet would PASS:
object:
- a
- b
key: value
2. With colons: {max-spaces-before: 1}
the following code snippet would PASS:
object :
- a
- b
the following code snippet would FAIL:
object :
- a
- b
3. With colons: {max-spaces-after: 2}
the following code snippet would PASS:
first: 1
second: 2
third: 3
the following code snippet would FAIL:
first: 1
2nd: 2
third: 3
commas
Use this rule to control the number of spaces before and after commas (,).
Options
• max-spaces-before defines the maximal number of spaces allowed before commas (use -1 to
disable).
• min-spaces-after defines the minimal number of spaces required after commas.
• max-spaces-after defines the maximal number of spaces allowed after commas (use -1 to
disable).
Default values (when enabled)
rules:
commas:
max-spaces-before: 0
min-spaces-after: 1
max-spaces-after: 1
Examples
1. With commas: {max-spaces-before: 0}
the following code snippet would PASS:
strange var:
[10, 20, 30, {x: 1, y: 2}]
the following code snippet would FAIL:
strange var:
[10, 20 , 30, {x: 1, y: 2}]
2. With commas: {max-spaces-before: 2}
the following code snippet would PASS:
strange var:
[10 , 20 , 30, {x: 1 , y: 2}]
3. With commas: {max-spaces-before: -1}
the following code snippet would PASS:
strange var:
[10,
20 , 30
, {x: 1, y: 2}]
4. With commas: {min-spaces-after: 1, max-spaces-after: 1}
the following code snippet would PASS:
strange var:
[10, 20, 30, {x: 1, y: 2}]
the following code snippet would FAIL:
strange var:
[10, 20,30, {x: 1, y: 2}]
5. With commas: {min-spaces-after: 1, max-spaces-after: 3}
the following code snippet would PASS:
strange var:
[10, 20, 30, {x: 1, y: 2}]
6. With commas: {min-spaces-after: 0, max-spaces-after: 1}
the following code snippet would PASS:
strange var:
[10, 20,30, {x: 1, y: 2}]
comments
Use this rule to control the position and formatting of comments.
Options
• Use require-starting-space to require a space character right after the #. Set to true
to enable, false to disable.
• Use ignore-shebangs to ignore a shebang at the beginning of the file when
require-starting-space is set.
• min-spaces-from-content is used to visually separate inline comments from content. It
defines the minimal required number of spaces between a comment and its preceding
content.
Default values (when enabled)
rules:
comments:
require-starting-space: true
ignore-shebangs: true
min-spaces-from-content: 2
Examples
1. With comments: {require-starting-space: true}
the following code snippet would PASS:
# This sentence
# is a block comment
the following code snippet would PASS:
##############################
## This is some documentation
the following code snippet would FAIL:
#This sentence
#is a block comment
2. With comments: {min-spaces-from-content: 2}
the following code snippet would PASS:
x = 2 ^ 127 - 1 # Mersenne prime number
the following code snippet would FAIL:
x = 2 ^ 127 - 1 # Mersenne prime number
comments-indentation
Use this rule to force comments to be indented like content.
Examples
1. With comments-indentation: {}
the following code snippet would PASS:
# Fibonacci
[0, 1, 1, 2, 3, 5]
the following code snippet would FAIL:
# Fibonacci
[0, 1, 1, 2, 3, 5]
the following code snippet would PASS:
list:
- 2
- 3
# - 4
- 5
the following code snippet would FAIL:
list:
- 2
- 3
# - 4
- 5
the following code snippet would PASS:
# This is the first object
obj1:
- item A
# - item B
# This is the second object
obj2: []
the following code snippet would PASS:
# This sentence
# is a block comment
the following code snippet would FAIL:
# This sentence
# is a block comment
document-end
Use this rule to require or forbid the use of document end marker (...).
Options
• Set present to true when the document end marker is required, or to false when it is
forbidden.
Default values (when enabled)
rules:
document-end:
present: true
Examples
1. With document-end: {present: true}
the following code snippet would PASS:
---
this:
is: [a, document]
...
---
- this
- is: another one
...
the following code snippet would FAIL:
---
this:
is: [a, document]
---
- this
- is: another one
...
2. With document-end: {present: false}
the following code snippet would PASS:
---
this:
is: [a, document]
---
- this
- is: another one
the following code snippet would FAIL:
---
this:
is: [a, document]
...
---
- this
- is: another one
document-start
Use this rule to require or forbid the use of document start marker (---).
Options
• Set present to true when the document start marker is required, or to false when it is
forbidden.
Default values (when enabled)
rules:
document-start:
present: true
Examples
1. With document-start: {present: true}
the following code snippet would PASS:
---
this:
is: [a, document]
---
- this
- is: another one
the following code snippet would FAIL:
this:
is: [a, document]
---
- this
- is: another one
2. With document-start: {present: false}
the following code snippet would PASS:
this:
is: [a, document]
...
the following code snippet would FAIL:
---
this:
is: [a, document]
...
empty-lines
Use this rule to set a maximal number of allowed consecutive blank lines.
Options
• max defines the maximal number of empty lines allowed in the document.
• max-start defines the maximal number of empty lines allowed at the beginning of the
file. This option takes precedence over max.
• max-end defines the maximal number of empty lines allowed at the end of the file. This
option takes precedence over max.
Default values (when enabled)
rules:
empty-lines:
max: 2
max-start: 0
max-end: 0
Examples
1. With empty-lines: {max: 1}
the following code snippet would PASS:
- foo:
- 1
- 2
- bar: [3, 4]
the following code snippet would FAIL:
- foo:
- 1
- 2
- bar: [3, 4]
empty-values
Use this rule to prevent nodes with empty content, that implicitly result in null values.
Options
• Use forbid-in-block-mappings to prevent empty values in block mappings.
• Use forbid-in-flow-mappings to prevent empty values in flow mappings.
Default values (when enabled)
rules:
empty-values:
forbid-in-block-mappings: true
forbid-in-flow-mappings: true
Examples
1. With empty-values: {forbid-in-block-mappings: true}
the following code snippets would PASS:
some-mapping:
sub-element: correctly indented
explicitly-null: null
the following code snippets would FAIL:
some-mapping:
sub-element: incorrectly indented
implicitly-null:
2. With empty-values: {forbid-in-flow-mappings: true}
the following code snippet would PASS:
{prop: null}
{a: 1, b: 2, c: 3}
the following code snippets would FAIL:
{prop: }
{a: 1, b:, c: 3}
float-values
Use this rule to limit the permitted values for floating-point numbers. YAML permits
three classes of float expressions: approximation to real numbers, positive and negative
infinity and "not a number".
Options
• Use require-numeral-before-decimal to require floats to start with a numeral (ex 0.0
instead of .0).
• Use forbid-scientific-notation to forbid scientific notation.
• Use forbid-nan to forbid NaN (not a number) values.
• Use forbid-inf to forbid infinite values.
Default values (when enabled)
rules:
float-values:
forbid-inf: false
forbid-nan: false
forbid-scientific-notation: false
require-numeral-before-decimal: false
Examples
1. With float-values: {require-numeral-before-decimal: true}
the following code snippets would PASS:
anemometer:
angle: 0.0
the following code snippets would FAIL:
anemometer:
angle: .0
2. With float-values: {forbid-scientific-notation: true}
the following code snippets would PASS:
anemometer:
angle: 0.00001
the following code snippets would FAIL:
anemometer:
angle: 10e-6
3. With float-values: {forbid-nan: true}
the following code snippets would FAIL:
anemometer:
angle: .NaN
1. With float-values: {forbid-inf: true}
the following code snippets would FAIL:
anemometer:
angle: .inf
hyphens
Use this rule to control the number of spaces after hyphens (-).
Options
• max-spaces-after defines the maximal number of spaces allowed after hyphens.
Default values (when enabled)
rules:
hyphens:
max-spaces-after: 1
Examples
1. With hyphens: {max-spaces-after: 1}
the following code snippet would PASS:
- first list:
- a
- b
- - 1
- 2
- 3
the following code snippet would FAIL:
- first list:
- a
- b
the following code snippet would FAIL:
- - 1
- 2
- 3
2. With hyphens: {max-spaces-after: 3}
the following code snippet would PASS:
- key
- key2
- key42
the following code snippet would FAIL:
- key
- key2
- key42
indentation
Use this rule to control the indentation.
Options
• spaces defines the indentation width, in spaces. Set either to an integer (e.g. 2 or 4,
representing the number of spaces in an indentation level) or to consistent to allow any
number, as long as it remains the same within the file.
• indent-sequences defines whether block sequences should be indented or not (when in a
mapping, this indentation is not mandatory -- some people perceive the - as part of the
indentation). Possible values: true, false, whatever and consistent. consistent requires
either all block sequences to be indented, or none to be. whatever means either
indenting or not indenting individual block sequences is OK.
• check-multi-line-strings defines whether to lint indentation in multi-line strings. Set
to true to enable, false to disable.
Default values (when enabled)
rules:
indentation:
spaces: consistent
indent-sequences: true
check-multi-line-strings: false
Examples
1. With indentation: {spaces: 1}
the following code snippet would PASS:
history:
- name: Unix
date: 1969
- name: Linux
date: 1991
nest:
recurse:
- haystack:
needle
2. With indentation: {spaces: 4}
the following code snippet would PASS:
history:
- name: Unix
date: 1969
- name: Linux
date: 1991
nest:
recurse:
- haystack:
needle
the following code snippet would FAIL:
history:
- name: Unix
date: 1969
- name: Linux
date: 1991
nest:
recurse:
- haystack:
needle
3. With indentation: {spaces: consistent}
the following code snippet would PASS:
history:
- name: Unix
date: 1969
- name: Linux
date: 1991
nest:
recurse:
- haystack:
needle
the following code snippet would FAIL:
some:
Russian:
dolls
4. With indentation: {spaces: 2, indent-sequences: false}
the following code snippet would PASS:
list:
- flying
- spaghetti
- monster
the following code snippet would FAIL:
list:
- flying
- spaghetti
- monster
5. With indentation: {spaces: 2, indent-sequences: whatever}
the following code snippet would PASS:
list:
- flying:
- spaghetti
- monster
- not flying:
- spaghetti
- sauce
6. With indentation: {spaces: 2, indent-sequences: consistent}
the following code snippet would PASS:
- flying:
- spaghetti
- monster
- not flying:
- spaghetti
- sauce
the following code snippet would FAIL:
- flying:
- spaghetti
- monster
- not flying:
- spaghetti
- sauce
7. With indentation: {spaces: 4, check-multi-line-strings: true}
the following code snippet would PASS:
Blaise Pascal:
Je vous écris une longue lettre parce que
je n'ai pas le temps d'en écrire une courte.
the following code snippet would PASS:
Blaise Pascal: Je vous écris une longue lettre parce que
je n'ai pas le temps d'en écrire une courte.
the following code snippet would FAIL:
Blaise Pascal: Je vous écris une longue lettre parce que
je n'ai pas le temps d'en écrire une courte.
the following code snippet would FAIL:
C code:
void main() {
printf("foo");
}
the following code snippet would PASS:
C code:
void main() {
printf("bar");
}
key-duplicates
Use this rule to prevent multiple entries with the same key in mappings.
Examples
1. With key-duplicates: {}
the following code snippet would PASS:
- key 1: v
key 2: val
key 3: value
- {a: 1, b: 2, c: 3}
the following code snippet would FAIL:
- key 1: v
key 2: val
key 1: value
the following code snippet would FAIL:
- {a: 1, b: 2, b: 3}
the following code snippet would FAIL:
duplicated key: 1
"duplicated key": 2
other duplication: 1
? >-
other
duplication
: 2
key-ordering
Use this rule to enforce alphabetical ordering of keys in mappings. The sorting order uses
the Unicode code point number as a default. As a result, the ordering is case-sensitive
and not accent-friendly (see examples below). This can be changed by setting the global
locale option. This allows one to sort case and accents properly.
Examples
1. With key-ordering: {}
the following code snippet would PASS:
- key 1: v
key 2: val
key 3: value
- {a: 1, b: 2, c: 3}
- T-shirt: 1
T-shirts: 2
t-shirt: 3
t-shirts: 4
- hair: true
hais: true
haïr: true
haïssable: true
the following code snippet would FAIL:
- key 2: v
key 1: val
the following code snippet would FAIL:
- {b: 1, a: 2}
the following code snippet would FAIL:
- T-shirt: 1
t-shirt: 2
T-shirts: 3
t-shirts: 4
the following code snippet would FAIL:
- haïr: true
hais: true
2. With global option locale: "en_US.UTF-8" and rule key-ordering: {}
as opposed to before, the following code snippet would now PASS:
- t-shirt: 1
T-shirt: 2
t-shirts: 3
T-shirts: 4
- hair: true
haïr: true
hais: true
haïssable: true
line-length
Use this rule to set a limit to lines length.
Options
• max defines the maximal (inclusive) length of lines.
• allow-non-breakable-words is used to allow non breakable words (without spaces inside)
to overflow the limit. This is useful for long URLs, for instance. Use true to allow,
false to forbid.
• allow-non-breakable-inline-mappings implies allow-non-breakable-words and extends it to
also allow non-breakable words in inline mappings.
Default values (when enabled)
rules:
line-length:
max: 80
allow-non-breakable-words: true
allow-non-breakable-inline-mappings: false
Examples
1. With line-length: {max: 70}
the following code snippet would PASS:
long sentence:
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do
eiusmod tempor incididunt ut labore et dolore magna aliqua.
the following code snippet would FAIL:
long sentence:
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod
tempor incididunt ut labore et dolore magna aliqua.
2. With line-length: {max: 60, allow-non-breakable-words: true}
the following code snippet would PASS:
this:
is:
- a:
http://localhost/very/very/very/very/very/very/very/very/long/url
# this comment is too long,
# but hard to split:
# http://localhost/another/very/very/very/very/very/very/very/very/long/url
the following code snippet would FAIL:
- this line is waaaaaaaaaaaaaay too long but could be easily split...
and the following code snippet would also FAIL:
- foobar: http://localhost/very/very/very/very/very/very/very/very/long/url
3. With line-length: {max: 60, allow-non-breakable-words: true,
allow-non-breakable-inline-mappings: true}
the following code snippet would PASS:
- foobar: http://localhost/very/very/very/very/very/very/very/very/long/url
4. With line-length: {max: 60, allow-non-breakable-words: false}
the following code snippet would FAIL:
this:
is:
- a:
http://localhost/very/very/very/very/very/very/very/very/long/url
new-line-at-end-of-file
Use this rule to require a new line character (\n) at the end of files.
The POSIX standard requires the last line to end with a new line character. All UNIX
tools expect a new line at the end of files. Most text editors use this convention too.
new-lines
Use this rule to force the type of new line characters.
Options
• Set type to unix to enforce UNIX-typed new line characters (\n), set type to dos to
enforce DOS-typed new line characters (\r\n), or set type to platform to infer the type
from the system running yamllint (\n on POSIX / UNIX / Linux / Mac OS systems or \r\n on
DOS / Windows systems).
Default values (when enabled)
rules:
new-lines:
type: unix
octal-values
Use this rule to prevent values with octal numbers. In YAML, numbers that start with 0 are
interpreted as octal, but this is not always wanted. For instance 010 is the city code of
Beijing, and should not be converted to 8.
Options
• Use forbid-implicit-octal to prevent numbers starting with 0.
• Use forbid-explicit-octal to prevent numbers starting with 0o.
Default values (when enabled)
rules:
octal-values:
forbid-implicit-octal: true
forbid-explicit-octal: true
Examples
1. With octal-values: {forbid-implicit-octal: true}
the following code snippets would PASS:
user:
city-code: '010'
the following code snippets would PASS:
user:
city-code: 010,021
the following code snippets would FAIL:
user:
city-code: 010
2. With octal-values: {forbid-explicit-octal: true}
the following code snippets would PASS:
user:
city-code: '0o10'
the following code snippets would FAIL:
user:
city-code: 0o10
quoted-strings
Use this rule to forbid any string values that are not quoted, or to prevent quoted
strings without needing it. You can also enforce the type of the quote used.
Options
• quote-type defines allowed quotes: single, double or any (default).
• required defines whether using quotes in string values is required (true, default) or
not (false), or only allowed when really needed (only-when-needed).
• extra-required is a list of PCRE regexes to force string values to be quoted, if they
match any regex. This option can only be used with required: false and required:
only-when-needed.
• extra-allowed is a list of PCRE regexes to allow quoted string values, even if required:
only-when-needed is set.
• allow-quoted-quotes allows (true) using disallowed quotes for strings with allowed
quotes inside. Default false.
Note: Multi-line strings (with | or >) will not be checked.
Default values (when enabled)
rules:
quoted-strings:
quote-type: any
required: true
extra-required: []
extra-allowed: []
allow-quoted-quotes: false
Examples
1. With quoted-strings: {quote-type: any, required: true}
the following code snippet would PASS:
foo: "bar"
bar: 'foo'
number: 123
boolean: true
the following code snippet would FAIL:
foo: bar
2. With quoted-strings: {quote-type: single, required: only-when-needed}
the following code snippet would PASS:
foo: bar
bar: foo
not_number: '123'
not_boolean: 'true'
not_comment: '# comment'
not_list: '[1, 2, 3]'
not_map: '{a: 1, b: 2}'
the following code snippet would FAIL:
foo: 'bar'
3. With quoted-strings: {required: false, extra-required: [^http://, ^ftp://]}
the following code snippet would PASS:
- localhost
- "localhost"
- "http://localhost"
- "ftp://localhost"
the following code snippet would FAIL:
- http://localhost
- ftp://localhost
4. With quoted-strings: {required: only-when-needed, extra-allowed: [^http://, ^ftp://],
extra-required: [QUOTED]}
the following code snippet would PASS:
- localhost
- "http://localhost"
- "ftp://localhost"
- "this is a string that needs to be QUOTED"
the following code snippet would FAIL:
- "localhost"
- this is a string that needs to be QUOTED
5. With quoted-strings: {quote-type: double, allow-quoted-quotes: false}
the following code snippet would PASS:
foo: "bar\"baz"
the following code snippet would FAIL:
foo: 'bar"baz'
6. With quoted-strings: {quote-type: double, allow-quoted-quotes: true}
the following code snippet would PASS:
foo: 'bar"baz'
trailing-spaces
Use this rule to forbid trailing spaces at the end of lines.
Examples
1. With trailing-spaces: {}
the following code snippet would PASS:
this document doesn't contain
any trailing
spaces
the following code snippet would FAIL:
this document contains
trailing spaces
on lines 1 and 3
truthy
Use this rule to forbid non-explicitly typed truthy values other than allowed ones (by
default: true and false), for example YES or off.
This can be useful to prevent surprises from YAML parsers transforming [yes, FALSE, Off]
into [true, false, false] or {y: 1, yes: 2, on: 3, true: 4, True: 5} into {y: 1, true: 5}.
Options
• allowed-values defines the list of truthy values which will be ignored during linting.
The default is ['true', 'false'], but can be changed to any list containing: 'TRUE',
'True', 'true', 'FALSE', 'False', 'false', 'YES', 'Yes', 'yes', 'NO', 'No', 'no', 'ON',
'On', 'on', 'OFF', 'Off', 'off'.
• check-keys disables verification for keys in mappings. By default, truthy rule applies
to both keys and values. Set this option to false to prevent this.
Default values (when enabled)
rules:
truthy:
allowed-values: ['true', 'false']
check-keys: true
Examples
1. With truthy: {}
the following code snippet would PASS:
boolean: true
object: {"True": 1, 1: "True"}
"yes": 1
"on": 2
"True": 3
explicit:
string1: !!str True
string2: !!str yes
string3: !!str off
encoded: !!binary |
True
OFF
pad== # this decodes as 'N»8Qii'
boolean1: !!bool true
boolean2: !!bool "false"
boolean3: !!bool FALSE
boolean4: !!bool True
boolean5: !!bool off
boolean6: !!bool NO
the following code snippet would FAIL:
object: {True: 1, 1: True}
the following code snippet would FAIL:
yes: 1
on: 2
True: 3
2. With truthy: {allowed-values: ["yes", "no"]}
the following code snippet would PASS:
- yes
- no
- "true"
- 'false'
- foo
- bar
the following code snippet would FAIL:
- true
- false
- on
- off
3. With truthy: {check-keys: false}
the following code snippet would PASS:
yes: 1
on: 2
true: 3
the following code snippet would FAIL:
yes: Yes
on: On
true: True
Disable with comments
Disabling checks for a specific line
To prevent yamllint from reporting problems for a specific line, add a directive comment
(# yamllint disable-line ...) on that line, or on the line above. For instance:
# The following mapping contains the same key twice,
# but I know what I'm doing:
key: value 1
key: value 2 # yamllint disable-line rule:key-duplicates
- This line is waaaaaaaaaay too long but yamllint will not report anything about it. # yamllint disable-line rule:line-length
This line will be checked by yamllint.
or:
# The following mapping contains the same key twice,
# but I know what I'm doing:
key: value 1
# yamllint disable-line rule:key-duplicates
key: value 2
# yamllint disable-line rule:line-length
- This line is waaaaaaaaaay too long but yamllint will not report anything about it.
This line will be checked by yamllint.
It is possible, although not recommend, to disabled all rules for a specific line:
# yamllint disable-line
- { all : rules ,are disabled for this line}
You can't make yamllint ignore invalid YAML syntax on a line (which generates a syntax
error), such as when templating a YAML file with Jinja. In some cases, you can workaround
this by putting the templating syntax in a YAML comment. See Putting template flow control
in comments.
If you need to disable multiple rules, it is allowed to chain rules like this: # yamllint
disable-line rule:hyphens rule:commas rule:indentation.
Disabling checks for all (or part of) the file
To prevent yamllint from reporting problems for the whole file, or for a block of lines
within the file, use # yamllint disable ... and # yamllint enable ... directive comments.
For instance:
# yamllint disable rule:colons
- Lorem : ipsum
dolor : sit amet,
consectetur : adipiscing elit
# yamllint enable rule:colons
- rest of the document...
It is possible, although not recommend, to disabled all rules:
# yamllint disable
- Lorem :
ipsum:
dolor : [ sit,amet]
- consectetur : adipiscing elit
# yamllint enable
If you need to disable multiple rules, it is allowed to chain rules like this: # yamllint
disable rule:hyphens rule:commas rule:indentation.
Disabling all checks for a file
To prevent yamllint from reporting problems for a specific file, add the directive comment
# yamllint disable-file as the first line of the file. For instance:
# yamllint disable-file
# The following mapping contains the same key twice, but I know what I'm doing:
key: value 1
key: value 2
- This line is waaaaaaaaaay too long but yamllint will not report anything about it.
or:
# yamllint disable-file
# This file is not valid YAML because it is a Jinja template
{% if extra_info %}
key1: value1
{% endif %}
key2: value2
Putting template flow control in comments
Alternatively for templating you can wrap the template statements in comments to make it a
valid YAML file. As long as the templating language doesn't use the same comment symbol,
it should be a valid template and valid YAML (pre and post-template processing).
Example of a Jinja2 code that cannot be parsed as YAML because it contains invalid tokens
{% and %}:
# This file IS NOT valid YAML and will produce syntax errors
{% if extra_info %}
key1: value1
{% endif %}
key2: value2
But it can be fixed using YAML comments:
# This file IS valid YAML because the Jinja is in a YAML comment
# {% if extra_info %}
key1: value1
# {% endif %}
key2: value2
Development
yamllint provides both a script and a Python module. The latter can be used to write your
own linting tools.
Basic example of running the linter from Python:
import yamllint
yaml_config = yamllint.config.YamlLintConfig("extends: default")
for p in yamllint.linter.run("example.yaml", yaml_config):
print(p.desc, p.line, p.rule)
class yamllint.linter.LintProblem(line, column, desc='<no description>', rule=None)
Represents a linting problem found by yamllint.
column Column on which the problem was found (starting at 1)
desc Human-readable description of the problem
line Line on which the problem was found (starting at 1)
rule Identifier of the rule that detected the problem
yamllint.linter.run(input, conf, filepath=None)
Lints a YAML source.
Returns a generator of LintProblem objects.
Parameters
• input -- buffer, string or stream to read from
• conf -- yamllint configuration object
Integration with text editors
Most text editors support syntax checking and highlighting, to visually report syntax
errors and warnings to the user. yamllint can be used to syntax-check YAML source, but a
bit of configuration is required depending on your favorite text editor.
Vim
Assuming that the ALE plugin is installed, yamllint is supported by default. It is
automatically enabled when editing YAML files.
If you instead use the syntastic plugin, add this to your .vimrc:
let g:syntastic_yaml_checkers = ['yamllint']
Neovim
Assuming that the neomake plugin is installed, yamllint is supported by default. It is
automatically enabled when editing YAML files.
Emacs
If you are flycheck user, you can use flycheck-yamllint integration.
Visual Studio Code
https://marketplace.visualstudio.com/items?itemName=fnando.linter
IntelliJ
https://plugins.jetbrains.com/plugin/15349-yamllint
Other text editors
Help wanted!
Your favorite text editor is not listed here? Help us improve by adding a section (by
opening a pull-request or issue on GitHub).
Integration with other software
Integration with pre-commit
You can integrate yamllint in pre-commit tool. Here is an example, to add in your
.pre-commit-config.yaml
---
# Update the rev variable with the release version that you want, from the yamllint repo
# You can pass your custom .yamllint with args attribute.
- repo: https://github.com/adrienverge/yamllint.git
rev: v1.17.0
hooks:
- id: yamllint
args: [-c=/path/to/.yamllint]
Integration with GitHub Actions
yamllint auto-detects when it's running inside of GitHub Actions and automatically uses
the suited output format to decorate code with linting errors. You can also force the
GitHub Actions output with yamllint --format github.
A minimal example workflow using GitHub Actions:
---
on: push # yamllint disable-line rule:truthy
jobs:
lint:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v3
- name: Install yamllint
run: pip install yamllint
- name: Lint YAML files
run: yamllint .
Integration with Arcanist
You can configure yamllint to run on arc lint. Here is an example .arclint file that makes
use of this configuration.
{
"linters": {
"yamllint": {
"type": "script-and-regex",
"script-and-regex.script": "yamllint",
"script-and-regex.regex": "/^(?P<line>\\d+):(?P<offset>\\d+) +(?P<severity>warning|error) +(?P<message>.*) +\\((?P<name>.*)\\)$/m",
"include": "(\\.(yml|yaml)$)"
}
}
}
AUTHOR
Adrien Vergé
COPYRIGHT
2023, Adrien Vergé