Install
prettier-eslint
Formats your JavaScript using prettier followed by eslint --fix
The problem
The fix feature of eslint is pretty great and can
auto-format/fix much of your code according to your ESLint config.
prettier is a more powerful automatic formatter. One of the nice
things about prettier is how opinionated it is. Unfortunately, it's not
opinionated enough and/or some opinions differ from my own. So after prettier
formats the code, I start getting linting errors.
This solution
This formats your code via prettier, and then passes the result of that to
eslint --fix. This way you can get the benefits of prettier's superior
formatting capabilities, but also benefit from the configuration capabilities of
eslint.
For files with an extension of
.css,.less,.scss, or.jsonthis only
runsprettiersinceeslintcannot process those.
Installation
This module is distributed via npm which is bundled with node and
should be installed as one of your project's devDependencies:
npm install --save-dev prettier-eslint
Usage
Example
const format = require('prettier-eslint');
// notice, no semicolon in the original text
const sourceCode = 'const {foo} = bar';
const options = {
text: sourceCode,
eslintConfig: {
parserOptions: {
ecmaVersion: 7
},
rules: {
semi: ['error', 'never']
}
},
prettierOptions: {
bracketSpacing: true
},
fallbackPrettierOptions: {
singleQuote: false
}
};
const formatted = await format(options);
// notice no semicolon in the formatted text
formatted; // const { foo } = bar
options
text (String)
The source code to format.
filePath (?String)
The path of the file being formatted can be used to override eslintConfig
(eslint will be used to find the relevant config for the file).
eslintConfig (?Object)
The config to use for formatting with ESLint. Can be overridden with filePath.
prettierOptions (?Object)
The options to pass for formatting with prettier. If not provided,
prettier-eslint will attempt to create the options based on the eslintConfig
(whether that's provided or derived via filePath). You can also provide some
of the options and have the remaining options derived via your eslint config.
This is useful for options like parser.
NOTE: these options override the eslint config. If you want the fallback
options to be used only in the case that the rule cannot be inferred from
eslint, see "fallbackPrettierOptions" below.
fallbackPrettierOptions (?Object)
The options to pass for formatting with prettier if prettier-eslint is not
able to create the options based on the the eslintConfig (whether that's
provided or derived via filePath). These options will only be used in the case
that the corresponding eslint rule cannot be found and the prettier option has
not been manually defined in prettierOptions. If the fallback is not given,
prettier-eslint will just use the default prettier value in this scenario.
logLevel (?Enum: ['trace', 'debug', 'info', 'warn', 'error', 'silent'])
prettier-eslint does quite a bit of logging if you want it to. Pass this to
set the number of logs you want to see. Default is process.env.LOG_LEVEL || 'warn'.
eslintPath (?String)
By default, prettier-eslint will try to find the relevant eslint (and
prettier) module based on the filePath. If it cannot find one, then it will
use the version that prettier-eslint has installed locally. If you'd like to
specify a path to the eslint module you would like to have prettier-eslint
use, then you can provide the full path to it with the eslintPath option.
prettierPath (?String)
This is basically the same as eslintPath except for the prettier module.
prettierLast (?Boolean)
By default, prettier-eslint will run prettier first, then eslint --fix.
This is great if you want to use prettier, but override some of the styles you
don't like using eslint --fix.
An alternative approach is to use different tools for different concerns. If you
provide prettierLast: true, it will run eslint --fix first, then prettier.
This allows you to use eslint to look for bugs and/or bad practices, and use
prettier to enforce code style.
throws
prettier-eslint will only propagate parsing errors when either prettier or eslint fails. In addition to propagating the errors, it will also log a specific message indicating what it was doing at the time of the failure.
Note: format will not show any message regarding broken rules in either prettier or eslint.
Capturing ESLint messages
const {analyze} = require("prettier-eslint");
const text = 'var x = 0;';
const result = await analyze({
text,
eslintConfig: {
rules: { 'no-var': 'error' }
}
})
console.log(result.messages);
produces on the console
[{
ruleId: 'no-var',
severity: 2,
message: 'Unexpected var, use let or const instead.',
line: 1,
column: 1,
nodeType: 'VariableDeclaration',
messageId: 'unexpectedVar',
endLine: 1,
endColumn: 11
}]
The additional export analyze is identical to format except that it
returns a simple object with properties output giving the exact string
that format would return, and messages giving the array of message
descriptions (with the structure shown above) produced by the eslint
analysis of the code. You may use analyze in place of format if you
would like to perform the formatting but also capture any errors that
eslint may notice.
Technical details
Code ➡️ prettier ➡️ eslint --fix ➡️ Formatted Code ✨
inferring prettierOptions via eslintConfig
The eslintConfig and prettierOptions can each be provided as an argument. If
the eslintConfig is not provided, then prettier-eslint will look for them
based on the fileName (if no fileName is provided then it uses
process.cwd()). Once prettier-eslint has found the eslintConfig, the
prettierOptions are inferred from the eslintConfig. If some of the
prettierOptions have already been provided, then prettier-eslint will only
infer the remaining options. This inference happens in src/utils.js.
An important thing to note about this inference is that it may not support
your specific eslint config. So you'll want to check src/utils.js to see how
the inference is done for each option (what rule(s) are referenced, etc.) and
make a pull request if your configuration is supported.
Defaults if you have all of the relevant ESLint rules disabled (or have
ESLint disabled entirely via /* eslint-disable */ then prettier options will
fall back to the prettier defaults:
{
printWidth: 80,
tabWidth: 2,
singleQuote: false,
trailingComma: 'none',
bracketSpacing: true,
semi: true,
useTabs: false,
// prettier-eslint doesn't currently support
// inferring these two (Pull Requests welcome):
parser: 'babylon',
bracketSameLine: false,
}
Troubleshooting
debugging issues
There is a lot of logging available with prettier-eslint. When debugging, you
can use one of the
logLevels to get a better
idea of what's going on. If you're using prettier-eslint-cli then you can use
the --log-level trace, if you're using the Atom plugin, then
you can open the developer tools and enter:
process.env.LOG_LEVEL = 'trace' in the console, then run the format. You'll
see a bunch of logs that should help you determine whether the problem is
prettier, eslint --fix, how prettier-eslint infers your prettier
options, or any number of other things. You will be asked to do this before
filing issues, so please do :smile:
NOTE: When you're doing this, it's recommended that you only run this on a
single file because there are a LOT of logs :)
eslint-disable-line
While using // eslint-disable-line, sometimes you may get linting errors after
the code has been processed by this module. That is because prettier changes
this:
// prettier-ignore
if (x) { // eslint-disable-line
}
to this:
if (x) {
// eslint-disable-line
}
And the eslint --fix wont change it back. You can notice that // eslint-disable-line has moved to a new line. To work around this issue, you can
use //eslint-disable-next-line instead of // eslint-disable-line like this:
// eslint-disable-next-line
if (x) {
}
Inspiration
Other Solutions
None that I'm aware of. Feel free to file a PR if you know of any other
solutions.
Related
prettier-eslint-cli-
Command Line Interfaceprettier-atom- Atom plugin (check the "ESlint integration"
checkbox in settings)vs-code-prettier-eslint- Visual Studio Code plugineslint-plugin-prettier-
ESLint plugin. While prettier-eslint useseslint --fixto change the output ofprettier, eslint-plugin-prettier keeps theprettieroutput as-is and integrates it with the regular ESLint workflow.prettier-eslint-webpack-plugin-
Prettier ESlint Webpack Plugin
Contributors
Thanks goes to these people (emoji key):
This project follows the all-contributors specification.
Contributions of any kind welcome!
LICENSE
MIT
