prettier-package-json is a JSON formatter inspired by prettier. It removes all original styling and ensures that the outputted package.json conforms to a consistent style. By default it uses opinionated defaults but can be configured to your individual needs.

Keys in package.json will be sorted in an opinionated order but may be configured to your own preferences.

Input:

{
  "description": "Prettier formatter for package.json files",
  "name": "prettier-package-json",
  "license": "MIT",
  "version": "1.0.1",
  "author": "Cameron Hunter <hello@cameronhunter.co.uk>"
}

Output:

{
  "name": "prettier-package-json",
  "description": "Prettier formatter for package.json files",
  "author": "Cameron Hunter <hello@cameronhunter.co.uk>",
  "license": "MIT",
  "version": "1.0.1"
}

The scripts field is sorted alphabetically but keeps pre and post scripts surrounding their named script.

Input:

{
  "name": "prettier-package-json",
  "version": "1.0.1",
  "scripts": {
    "test": "test",
    "pretest": "pretest",
    "version": "version",
    "postversion": "postversion",
    "build": "build"
  }
}

Output:

{
  "name": "prettier-package-json",
  "version": "1.0.1",
  "scripts": {
    "build": "build",
    "pretest": "pretest",
    "test": "test",
    "version": "version",
    "postversion": "postversion"
  }
}

The author, contributors and maintainers fields will be shortened to their string versions and sorted by name. Use the --expand-users option if you prefer user objects.

Input:

{
  "name": "prettier-package-json",
  "version": "1.0.1",
  "author": {
    "name": "Cameron Hunter",
    "email": "hello@cameronhunter.co.uk",
    "url": "https://cameronhunter.co.uk"
  },
  "contributors": ["Barry", "Adam <adam@email.com>"]
}

Output:

{
  "name": "prettier-package-json",
  "version": "1.0.1",
  "author": "Cameron Hunter <hello@cameronhunter.co.uk> (https://cameronhunter.co.uk)",
  "contributors": ["Adam <adam@email.com>", "Barry"]
}

Some files are included or excluded automatically by npm, these are removed from the files field before sorting alphabetically.

Input:

{
  "name": "prettier-package-json",
  "version": "1.0.1",
  "main": "src/index.js",
  "files": [
    "src/index.js",
    "src",
    "CHANGELOG.md",
    "readme.md",
    "package-lock.json"
  ]
}

Output:

{
  "name": "prettier-package-json",
  "version": "1.0.1",
  "main": "src/index.js",
  "files": ["src"]
}

Install:

yarn add prettier-package-json --dev

You can install it globally if you like:

yarn global add prettier-package-json

We're defaulting to yarn but you can use npm if you like:

npm install [-g] prettier-package-json

Run prettier-package-json through the CLI with this script. Run it without any arguments to see the options.

To format a file in-place, use --write. You may want to consider committing your file before doing that, just in case.

prettier-package-json [opts] [filename]

In practice, this may look something like:

prettier-package-json --write ./package.json

You can use this with a pre-commit tool. This can re-format your files that are marked as "staged" via git add before you commit.

Install it along with husky:

yarn add lint-staged husky --dev

and add this config to your package.json:

{
  "scripts": {
    "precommit": "lint-staged"
  },
  "lint-staged": {
    "package.json": ["prettier-package-json --write", "git add"]
  }
}

See https://github.com/okonet/lint-staged#configuration for more details about how you can configure lint-staged.

Alternately you can just save this script as .git/hooks/pre-commit and give it execute permission:

#!/bin/sh
packagejsonfiles=$(git diff --cached --name-only --diff-filter=ACM | grep 'package\.json$' | tr '\n' ' ')
[ -z "$packagejsonfiles" ] && exit 0

diffs=$(node_modules/.bin/prettier-package-json -l $packagejsonfiles)
[ -z "$diffs" ] && exit 0

echo "here"
echo >&2 "package.json files must be formatted with prettier-package-json. Please run:"
echo >&2 "node_modules/.bin/prettier-package-json --write "$diffs""

exit 1

The API has two functions, exported as format and check. Usage is as follows:

import { format, check } from 'prettier-package-json';

const options = {}; // optional

format(json, options);
check(json, options);

check checks to see if the file has been formatted with prettier-package-json given those options and returns a Boolean. This is similar to the --list-different parameter in the CLI and is useful for running in CI scenarios.

For usage in CI scenarios, you can use the --list-different CLI flag. The command will list all invalid files and return with a proper default error code, so that in case of an error or invalid file the build pipeline automatically fails.

These are the status codes:

• 0: all files valid, no error occured.
• 1: an error ocurred, for example a JSON parse error. See message on stderr for details.
• 2: not all files are valid.

These exit codes are only set when in --list-different mode.

prettier-package-json ships with a handful of customizable format options, usable in both the CLI, API, and configuration file.

A configuration file will be searched for using cosmiconfig rules:

• prettier-package-json field in package.json.
• prettier-package-json file (JSON or YAML), extentionless "rc" file.
• prettier-package-json file with the extensions .json, .yaml, .yml, .js, or .cjs.
• prettier-package-json.config.js or prettier-package-json.config.cjs CommonJS module.

Configuration file may also be passed using the --config CLI parameter.

See CONTRIBUTING.md.