# Introduction

[eslint-plugin-jsonc](https://www.npmjs.com/package/eslint-plugin-jsonc) is ESLint plugin for [JSON], [JSONC] and [JSON5] files.

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## :name_badge: Features

This ESLint plugin provides linting rules relate to better ways to help you avoid problems when using [JSON], [JSONC] and [JSON5].

- You can use ESLint to lint [JSON].
- You can apply rules similar to the rules you use for JavaScript to JSON using the [`"jsonc/auto"`](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/auto.html) rule provided by this plugin.
- You can choose the appropriate config provided by this plugin depending on whether you are using [JSON], [JSONC] or [JSON5].
- Supports [Vue SFC](https://vue-loader.vuejs.org/spec.html) custom blocks such as `<i18n>`.  
  Requirements `vue-eslint-parser` v7.3.0 and above.
- Supports ESLint directives. e.g. `// eslint-disable-next-line`
- You can check your code in real-time using the ESLint editor integrations.

You can check on the [Online DEMO](https://ota-meshi.github.io/eslint-plugin-jsonc/playground/).

## :question: Why is it ESLint plugin?

ESLint is a great linter for JavaScript.  
Since [JSON] is a subset of JavaScript, the same parser and rules can be applied to [JSON].  
Also, [JSONC] and [JSON5], which are variants of [JSON], are more similar to JavaScript than [JSON]. Applying a JavaScript linter to [JSON] is more rational than creating a JSON-specific linter.

### How does `eslint-plugin-jsonc` work?

This plugin parses `.json` with its own parser, but this parser just converts AST parsed by `acorn` (It is used internally by the ESLint standard parser) into AST with another name. However, ASTs that do not exist in [JSON] and the superset of JSON syntaxes are reported as parsing errors. By converting the AST to another name, we prevent false positives from ESLint core rules.  
Moreover, You can do the same linting using the extended rules of the ESLint core rules provided by this plugin.

The parser package used by this plugin is [jsonc-eslint-parser].

## :question: How is it different from other JSON plugins?

### Plugins that do not use AST

e.g. [eslint-plugin-json](https://www.npmjs.com/package/eslint-plugin-json)

These plugins use the processor to parse and return the results independently, without providing the ESLint engine with AST and source code text.

Plugins don't provide AST, so you can't use directive comments (e.g. `/* eslint-disable */`).  
Plugins don't provide source code text, so you can't use it with plugins and rules that use text (e.g. [eslint-plugin-prettier](https://github.com/prettier/eslint-plugin-prettier), [eol-last](https://eslint.org/docs/rules/eol-last)).  
Also, most plugins don't support JSON5.

**eslint-plugin-jsonc** works by providing AST and source code text to ESLint.

### Plugins that use the same AST as JavaScript

e.g. [eslint-plugin-json-files](https://www.npmjs.com/package/eslint-plugin-json-files), [eslint-plugin-json-es](https://www.npmjs.com/package/eslint-plugin-json-es)

These plugins use the same AST as JavaScript for linting.

Since the plugin uses the same AST as JavaScript, it may not report syntax that is not available in JSON (e.g. `1 + 1`, `(42)`). Also, ESLint core rules and other plugin rules can false positives (e.g. [quote-props](https://eslint.org/docs/rules/quote-props) rule reports quote on keys), which can complicate the your configuration.

The AST used by **eslint-plugin-jsonc** is similar to JavaScript AST, but with a different node name. This will prevent false positives. This means that it can be easily used in combination with other plugins.

<!--DOCS_IGNORE_START-->

## :book: Documentation

See [documents](https://ota-meshi.github.io/eslint-plugin-jsonc/).

## :cd: Installation

```bash
npm install --save-dev eslint eslint-plugin-jsonc
```

> **Requirements**
>
> - ESLint v6.0.0 and above
> - Node.js v12.22.x, v14.17.x, v16.x and above

<!--DOCS_IGNORE_END-->

## :book: Usage

<!--USAGE_SECTION_START-->
<!--USAGE_GUIDE_START-->

### Configuration

Use `.eslintrc.*` file to configure rules. See also: [https://eslint.org/docs/user-guide/configuring](https://eslint.org/docs/user-guide/configuring).

Example **.eslintrc.js**:

```js
module.exports = {
  extends: [
    // add more generic rulesets here, such as:
    // 'eslint:recommended',
    "plugin:jsonc/recommended-with-jsonc",
  ],
  rules: {
    // override/add rules settings here, such as:
    // 'jsonc/rule-name': 'error'
  },
};
```

This plugin provides configs:

- `plugin:jsonc/base` ... Configuration to enable correct JSON parsing.
- `plugin:jsonc/recommended-with-json` ... Recommended configuration for JSON.
- `plugin:jsonc/recommended-with-jsonc` ... Recommended configuration for JSONC.
- `plugin:jsonc/recommended-with-json5` ... Recommended configuration for JSON5.
- `plugin:jsonc/prettier` ... Turn off rules that may conflict with [Prettier](https://prettier.io/).
- `plugin:jsonc/all` ... Enables all rules. It's meant for testing, not for production use because it changes with every minor and major version of the plugin. Use it at your own risk.

This plugin will parse `.json`, `.jsonc` and `.json5` by default using the configuration provided by the plugin (unless you already have a parser configured - see below).

See [the rule list](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/) to get the `rules` that this plugin provides.

#### Parser Configuration

If you have already specified a parser in your `.eslintrc`, you will also need to manually configure the parser for JSON files (your parser config takes priority over that defined by `extends` shared configs).

For example, if you are using the `"@babel/eslint-parser"`, configure it as follows:

```js
module.exports = {
  // ...
  extends: ["plugin:jsonc/recommended-with-jsonc"],
  // ...
  parser: "@babel/eslint-parser",
  // Add an `overrides` section to add a parser configuration for json.
  overrides: [
    {
      files: ["*.json", "*.json5", "*.jsonc"],
      parser: "jsonc-eslint-parser",
    },
  ],
  // ...
};
```

## :computer: Editor Integrations

### Visual Studio Code

Use the [dbaeumer.vscode-eslint](https://marketplace.visualstudio.com/items?itemName=dbaeumer.vscode-eslint) extension that Microsoft provides officially.

You have to configure the `eslint.validate` option of the extension to check `.json` files, because the extension targets only `*.js` or `*.jsx` files by default.

Example **.vscode/settings.json**:

```json
{
  "eslint.validate": ["javascript", "javascriptreact", "json", "jsonc", "json5"]
}
```

<!--USAGE_GUIDE_END-->
<!--USAGE_SECTION_END-->

## :white_check_mark: Rules

<!--RULES_SECTION_START-->

The `--fix` option on the [command line](https://eslint.org/docs/user-guide/command-line-interface#fixing-problems) automatically fixes problems reported by rules which have a wrench :wrench: below.  
The rules with the following star :star: are included in the config.

<!--RULES_TABLE_START-->

### JSONC Rules

| Rule ID | Description | Fixable | JSON | JSONC | JSON5 |
|:--------|:------------|:-------:|:----:|:-----:|:-----:|
| [jsonc/auto](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/auto.html) | apply jsonc rules similar to your configured ESLint core rules | :wrench: |  |  |  |
| [jsonc/key-name-casing](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/key-name-casing.html) | enforce naming convention to property key names |  |  |  |  |
| [jsonc/no-bigint-literals](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-bigint-literals.html) | disallow BigInt literals |  | :star: | :star: | :star: |
| [jsonc/no-binary-expression](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-binary-expression.html) | disallow binary expression | :wrench: | :star: | :star: | :star: |
| [jsonc/no-binary-numeric-literals](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-binary-numeric-literals.html) | disallow binary numeric literals | :wrench: | :star: | :star: | :star: |
| [jsonc/no-comments](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-comments.html) | disallow comments |  | :star: |  |  |
| [jsonc/no-escape-sequence-in-identifier](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-escape-sequence-in-identifier.html) | disallow escape sequences in identifiers. | :wrench: | :star: | :star: | :star: |
| [jsonc/no-hexadecimal-numeric-literals](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-hexadecimal-numeric-literals.html) | disallow hexadecimal numeric literals | :wrench: | :star: | :star: |  |
| [jsonc/no-infinity](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-infinity.html) | disallow Infinity |  | :star: | :star: |  |
| [jsonc/no-nan](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-nan.html) | disallow NaN |  | :star: | :star: |  |
| [jsonc/no-number-props](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-number-props.html) | disallow number property keys | :wrench: | :star: | :star: | :star: |
| [jsonc/no-numeric-separators](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-numeric-separators.html) | disallow numeric separators | :wrench: | :star: | :star: | :star: |
| [jsonc/no-octal-numeric-literals](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-octal-numeric-literals.html) | disallow octal numeric literals | :wrench: | :star: | :star: | :star: |
| [jsonc/no-parenthesized](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-parenthesized.html) | disallow parentheses around the expression | :wrench: | :star: | :star: | :star: |
| [jsonc/no-plus-sign](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-plus-sign.html) | disallow plus sign | :wrench: | :star: | :star: |  |
| [jsonc/no-regexp-literals](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-regexp-literals.html) | disallow RegExp literals |  | :star: | :star: | :star: |
| [jsonc/no-template-literals](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-template-literals.html) | disallow template literals | :wrench: | :star: | :star: | :star: |
| [jsonc/no-undefined-value](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-undefined-value.html) | disallow `undefined` |  | :star: | :star: | :star: |
| [jsonc/no-unicode-codepoint-escapes](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-unicode-codepoint-escapes.html) | disallow Unicode code point escape sequences. | :wrench: | :star: | :star: | :star: |
| [jsonc/sort-array-values](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/sort-array-values.html) | require array values to be sorted | :wrench: |  |  |  |
| [jsonc/sort-keys](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/sort-keys.html) | require object keys to be sorted | :wrench: |  |  |  |
| [jsonc/valid-json-number](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/valid-json-number.html) | disallow invalid number for JSON | :wrench: | :star: | :star: |  |
| [jsonc/vue-custom-block/no-parsing-error](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/vue-custom-block/no-parsing-error.html) | disallow parsing errors in Vue custom blocks |  | :star: | :star: | :star: |

### Extension Rules

| Rule ID | Description | Fixable | JSON | JSONC | JSON5 |
|:--------|:------------|:-------:|:----:|:-----:|:-----:|
| [jsonc/array-bracket-newline](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/array-bracket-newline.html) | enforce line breaks after opening and before closing array brackets | :wrench: |  |  |  |
| [jsonc/array-bracket-spacing](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/array-bracket-spacing.html) | disallow or enforce spaces inside of brackets | :wrench: |  |  |  |
| [jsonc/array-element-newline](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/array-element-newline.html) | enforce line breaks between array elements | :wrench: |  |  |  |
| [jsonc/comma-dangle](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/comma-dangle.html) | require or disallow trailing commas | :wrench: | :star: |  |  |
| [jsonc/comma-style](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/comma-style.html) | enforce consistent comma style | :wrench: |  |  |  |
| [jsonc/indent](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/indent.html) | enforce consistent indentation | :wrench: |  |  |  |
| [jsonc/key-spacing](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/key-spacing.html) | enforce consistent spacing between keys and values in object literal properties | :wrench: |  |  |  |
| [jsonc/no-dupe-keys](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-dupe-keys.html) | disallow duplicate keys in object literals |  | :star: | :star: | :star: |
| [jsonc/no-floating-decimal](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-floating-decimal.html) | disallow leading or trailing decimal points in numeric literals | :wrench: | :star: | :star: |  |
| [jsonc/no-multi-str](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-multi-str.html) | disallow multiline strings |  | :star: | :star: |  |
| [jsonc/no-octal-escape](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-octal-escape.html) | disallow octal escape sequences in string literals |  |  |  |  |
| [jsonc/no-octal](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-octal.html) | disallow legacy octal literals |  | :star: | :star: | :star: |
| [jsonc/no-sparse-arrays](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-sparse-arrays.html) | disallow sparse arrays |  | :star: | :star: | :star: |
| [jsonc/no-useless-escape](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/no-useless-escape.html) | disallow unnecessary escape usage |  | :star: | :star: | :star: |
| [jsonc/object-curly-newline](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/object-curly-newline.html) | enforce consistent line breaks inside braces | :wrench: |  |  |  |
| [jsonc/object-curly-spacing](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/object-curly-spacing.html) | enforce consistent spacing inside braces | :wrench: |  |  |  |
| [jsonc/object-property-newline](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/object-property-newline.html) | enforce placing object properties on separate lines | :wrench: |  |  |  |
| [jsonc/quote-props](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/quote-props.html) | require quotes around object literal property names | :wrench: | :star: | :star: |  |
| [jsonc/quotes](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/quotes.html) | enforce use of double or single quotes | :wrench: | :star: | :star: |  |
| [jsonc/space-unary-ops](https://ota-meshi.github.io/eslint-plugin-jsonc/rules/space-unary-ops.html) | disallow spaces after unary operators | :wrench: | :star: | :star: | :star: |

<!--RULES_TABLE_END-->
<!--RULES_SECTION_END-->

## :rocket: To Do More Verification

### Verify using JSON Schema

You can verify using JSON Schema by checking and installing [eslint-plugin-json-schema-validator].

### Verify the [Vue I18n] message resource files

You can verify the message files by checking and installing [@intlify/eslint-plugin-vue-i18n].

<!--DOCS_IGNORE_START-->

## :traffic_light: Semantic Versioning Policy

**eslint-plugin-jsonc** follows [Semantic Versioning](http://semver.org/) and [ESLint's Semantic Versioning Policy](https://github.com/eslint/eslint#semantic-versioning-policy).

## :beers: Contributing

Welcome contributing!

Please use GitHub's Issues/PRs.

### Development Tools

- `npm test` runs tests and measures coverage.
- `npm run update` runs in order to update readme and recommended configuration.

<!--DOCS_IGNORE_END-->

## :couple: Related Packages

- [eslint-plugin-yml](https://github.com/ota-meshi/eslint-plugin-yml) ... ESLint plugin for YAML.
- [eslint-plugin-toml](https://github.com/ota-meshi/eslint-plugin-toml) ... ESLint plugin for TOML.
- [eslint-plugin-json-schema-validator](https://github.com/ota-meshi/eslint-plugin-json-schema-validator) ... ESLint plugin that validates data using JSON Schema Validator.
- [jsonc-eslint-parser](https://github.com/ota-meshi/jsonc-eslint-parser) ... JSON, JSONC and JSON5 parser for use with ESLint plugins.
- [yaml-eslint-parser](https://github.com/ota-meshi/yaml-eslint-parser) ... YAML parser for use with ESLint plugins.
- [toml-eslint-parser](https://github.com/ota-meshi/toml-eslint-parser) ... TOML parser for use with ESLint plugins.

## :lock: License

See the [LICENSE](LICENSE) file for license rights and limitations (MIT).

[json]: https://json.org/
[jsonc]: https://github.com/microsoft/node-jsonc-parser
[json5]: https://json5.org/
[jsonc-eslint-parser]: https://github.com/ota-meshi/jsonc-eslint-parser
[eslint-plugin-json-schema-validator]: https://github.com/ota-meshi/eslint-plugin-json-schema-validator
[@intlify/eslint-plugin-vue-i18n]: https://github.com/intlify/eslint-plugin-vue-i18n
[vue i18n]: https://github.com/intlify/vue-i18n-next
