eslint-plugin-json

Eslint plugin for JSON files

⚠️ Starting from major 2.0, rules need to be explicitly activated. See here the minimal config to add 🚨

Installation

Install eslint-plugin-json along eslint:

$ npm install --save-dev eslint eslint-plugin-json
# or
$ yarn add --dev eslint eslint-plugin-json

Note: If you installed ESLint globally (using the -g flag) then you must also install eslint-plugin-json globally.

Usage

Basic configuration

The json plugin ship with two recommended config you can use to easily activate it via the extends key. It comes in two flavor: one strict (recommended) and one allowing comments recommended-with-comments.

{
    "extends": ["plugin:json/recommended"]
}

You can run ESLint on individual JSON files or you can use the --ext flag to add JSON files to the list.

eslint . --ext .json,.js
eslint example.json

Custom Configuration

If you want more granular control over which rules, and wich severity you want

Add json to the list of plugins (You can omit the eslint-plugin- prefix) Then pick your rules.

If you want them all, add the json/json rule (or its alias json/*). (this is what the recommended config does)

Global rules

The global rules (json/json or its alias json/*) activate all the rules. Note it can be configured to ignore errors cause by comments. To do so, add option 'allowComments' or {allowComments: true}

For instance:

{
    "plugins": [
        "json"
    ],
    "rules": {
        "json/*": ["error", "allowComments"],
        // or the equivalent:
        "json/*": ["error", {"allowComments": true}]
    }
}

Individual Rules

Here is the list of individual rules (with name in kebab-case)in case you want granular error/warning level:

json/undefined
json/enum-value-mismatch
json/unexpected-end-of-comment
json/unexpected-end-of-string
json/unexpected-end-of-number
json/invalid-unicode
json/invalid-escape-character
json/invalid-character
json/property-expected
json/comma-expected
json/colon-expected
json/value-expected
json/comma-or-close-backet-expected
json/comma-or-close-brace-expected
json/trailing-comma
json/duplicate-key
json/comment-not-permitted
json/schema-resolve-error
json/unknown (error that does not match previous ones)

FAQs

How does eslint-plugin-json work?

Starting from version 1.3, this plugin relies on what VSCode uses for its implementation of JSON validation.

Originaly this plugin used to use JSHint, however due to heavy dependencies, it was replaced.

Why doesn't this plugin use `eslint` itself or just `JSON.parse`?

eslint's parser is a JavaScript parser. JSON is a stricter subset and things that are valid JavaScript are not valid JSON. This is why something more specific is more appropriate.

While JSON.parse seems ideal, it is not designed to continue after the first error. So if you have a missing trailing comma in the start of the file, the rest of the file will go unlinted. A smarter parser that can self-correct after seeing errors is needed which the VSCode implementation provides by leveraging the jsonc-parser module.

Will this plugin provide more configuration?

It is now possible as you can see in the Configuration section

Additionally, support for autofixing common errors could be added in the feature.

Is `eslint` really the best tool to lint my JSON?

Not really. eslint plugin interface wasn't designed to lint a completely different language but its interface is flexible enough to allow it. So this plugin is certainly unusual.

Ideally, your editor would natively supports linting JSON. If it doesn't though, then might as well use this plugin. Hacky linting is better than no linting :)

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