remark-lint is a markdown code style linter. Another linter? Yes. Ensuring the markdown you (and contributors) write is of great quality will provide better rendering in all the different markdown parsers, and makes sure less refactoring is needed afterwards.
What is quality? That’s up to you, but there are sensible presets.
remark-lint is built on remark, a powerful markdown processor powered by plugins (such as this one).
- Installation
- Command line
- Programmatic
- Rules
- Configuring remark-lint
- Using remark to fix your markdown
- Editor Integrations
- List of Presets
- List of External Rules
- Related
- License
npm:
npm install remark-lint
Use remark-lint
with remark-cli
, and a preset.
npm install --save remark-cli remark-preset-lint-recommended
Then, configure remark in your package.json
:
// ...
"scripts": {
"lint-md": "remark ."
},
// ...
"remarkConfig": {
"plugins": ["remark-preset-lint-recommended"]
}
// ...
Let’s say there’s an example.md
, which looks as follows:
* Hello
[World][]
Now, running our lint-md
script with npm, npm run lint-md
, yields:
example.md
1:3 warning Incorrect list-item indent: add 2 spaces list-item-indent
3:1-3:10 warning Found reference to undefined definition no-undefined-references
⚠ 2 warnings
See doc/rules.md
for what those warnings are (and how to
turn them off).
Use remark-lint
together with remark
:
npm install remark remark-lint remark-lint-first-heading-level
Let’s say example.js
looks as follows:
var report = require('vfile-reporter');
var remark = require('remark');
var styleGuide = require('remark-preset-lint-markdown-style-guide');
var file = remark().use(styleGuide).processSync('_Hello world_');
console.log(report(file));
Now, running node example.js
yields:
1:1-1:14 warning Emphasis should use `*` as a marker emphasis-marker remark-lint
⚠ 1 warning
doc/rules.md
lists all available official rules.
remark-lint is a remark plug-in and supports configuration through its configuration files.
An example .remarkrc
file could look as follows:
{
"plugins": [
"remark-preset-lint-recommended",
["remark-lint-list-item-indent", false]
]
}
Where the object at plugins.lint
is a map of ruleId
s and
their values, which precede over presets.
Using our example.md
from before:
* Hello
[World][]
Now, running npm run lint-md
yields:
example.md
3:1-3:10 warning Found reference to undefined definition no-undefined-references
⚠ 2 warnings
In addition, you can also provide configuration comments to turn a rule
on or off inside a file. Note that you cannot change what a setting,
such as maximum-line-length
, just whether they are shown or not.
Read more about configuration comments in
remark-message-controls documentation.
The following file will warn twice for the duplicate headings:
# Hello
## Hello
### Hello
The following file will warn once (the second heading is ignored, but the third is re-enabled):
# Hello
<!--lint disable no-duplicate-headings-->
## Hello
<!--lint enable no-duplicate-headings-->
### Hello
Note: You’ll need the blank lines between comments and other nodes!
remark-stringify
can format markdown syntax. It ensures a
single style is used: list items use one type of bullet (*
, -
, +
),
emphasis (*
or _
) and importance (__
or **
) use a standard marker, table
fences are aligned, and more.
If you require('remark')
, remark-stringify
is included
unless an output format other than markdown (such as HTML) is defined.
Say we have the following file, example.js
, showing how formatting rules can
be used:
var report = require('vfile-reporter');
var remark = require('remark');
var emphasisMarker = require('remark-lint-emphasis-marker');
var strongMarker = require('remark-lint-strong-marker');
remark()
.use(emphasisMarker, '*')
.use(strongMarker, '*')
// ^ two `remark-lint` rules.
.use({
settings: {emphasis: '*', strong: '*'}
// ^ `remark-stringify` settings.
})
.process('_Hello_, __world__!', function (err, file) {
console.error(report(err || file));
console.log(String(file));
});
Now, running node example
yields warnings and a formatted file:
1:1-1:8 warning Emphasis should use `*` as a marker emphasis-marker remark-lint
1:10-1:19 warning Strong should use `*` as a marker strong-marker remark-lint
⚠ 2 warnings
*Hello*, **world**!
If you’re using remark-stringify
yourself, you can pass
options like any other plugin, like so:
var report = require('vfile-reporter');
var unified = require('unified');
var parse = require('remark-parse');
var stringify = require('remark-stringify');
var emphasisMarker = require('remark-lint-emphasis-marker');
var strongMarker = require('remark-lint-strong-marker');
unified()
.use(parse)
.use(emphasisMarker, '*')
.use(strongMarker, '*')
// ^ two `remark-lint` rules.
.use(stringify, {emphasis: '*', strong: '*'})
// ^ `remark-stringify` with settings.
.process('_Hello_, __world__!', function (err, file) {
console.error(report(err || file));
console.log(String(file));
});
Now, when running node example
, this results in the same output as the
previous example.
If you’re using remark-cli
, remark-stringify
is
included unless an output format other than markdown (such as HTML) is defined.
In this case you can configure remark-stringify
settings using the -s, --settings
flag or a "settings"
property in remark
configuration files.
Say we have the following file, example.md
:
_Hello_, __world__!
And our package.json
looks as follows:
// ...
"remarkConfig": {
"settings": {
"emphasis": "*",
"strong": "*"
},
"plugins": [
"remark-lint-emphasis-marker",
"remark-lint-strong-marker"
]
}
// ...
Now, running remark example.md
yields warnings and a formatted file:
*Hello*, **world**!
example.md
1:1-1:8 warning Emphasis should use `*` as a marker emphasis-marker remark-lint
1:10-1:19 warning Strong should use `*` as a marker strong-marker remark-lint
⚠ 2 warnings
Note: running
remark example.md -o
orremark example.md --output
overwritesexample.md
and formats it. So, if you’d run that twice (the first pass lints and fixes the markdown, the second pass checks it again), you’d see the outputexample.md: written
as all warnings are now fixed.
Currently, remark-lint is integrated with Atom through linter-markdown.
If you want to run all of remark from Atom, use linter-remark.
To run remark, optionally with remark-lint from Gulp, use gulp-remark.
I’m very interested in more integrations. Let me know if I can help.
Presets can be loaded through the preset
setting.
remark-preset-lint-consistent
— rules that enforce consistencyremark-preset-lint-markdown-style-guide
— rules that enforce the markdown style guideremark-preset-lint-recommended
— rules that prevent mistakes or syntaxes that do not work correctly across vendors
External rules can be loaded just like normal rules.
remark-lint-alphabetize-lists
— Ensure list items are in alphabetical orderremark-lint-appropriate-heading
— Check that the top-level heading matches the directory nameremark-lint-blank-lines-1-0-2
— Ensure a specific number of lines between blocksremark-lint-books-links
— Ensure links in lists of books follow a standard formatremark-lint-code
— Lint fenced code blocks by corresponding language tags, currently supporting ESLintremark-lint-no-dead-urls
— Check that external links are aliveremark-lint-emoji-limit
— Enforce a limit of emoji per paragraphremark-lint-no-empty-sections
— Ensure every heading is followed by content (forming a section)remark-lint-heading-length
— Ensure headings have the appropriate lengthremark-lint-no-leading-spaces
—⚠️ Warn about leading white-spaceremark-lint-list-item-punctuation
—⚠️ check if list items end in periodsremark-lint-are-links-valid
— Check if your links are reachable and/or uniqueremark-lint-sentence-newline
—⚠️ Ensure sentences are followed by a newlineremark-lint-no-trailing-spaces
—⚠️ Warn about trailing white-spaceremark-lint-no-url-trailing-slash
— Ensure that thehref
of links has no trailing slashremark-lint-write-good
— Wrapper for write-good
remark-validate-links
— Validate if links point to existing headings and files in markdown