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feat(eslint-plugin): add rule naming-conventions (#1318)
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| # Enforces naming conventions for everything across a codebase (`naming-convention`) | ||
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| Enforcing naming conventions helps keep the codebase consistent, and reduces overhead when thinking about how to name a variable. | ||
| Additionally, a well designed style guide can help communicate intent, such as by enforcing all private properties begin with an `_`, and all global-level constants are written in `UPPER_CASE`. | ||
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| There are many different rules that have existed over time, but they have had the problem of not having enough granularity, meaning it was hard to have a well defined style guide, and most of the time you needed 3 or more rules at once to enforce different conventions, hoping they didn't conflict. | ||
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| ## Rule Details | ||
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| This rule allows you to enforce conventions for any identifier, using granular selectors to create a fine-grained style guide. | ||
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| ### Note - this rule only needs type information in specific cases, detailed below | ||
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| ## Options | ||
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| This rule accepts an array of objects, with each object describing a different naming convention. | ||
| Each property will be described in detail below. Also see the examples section below for illustrated examples. | ||
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| ```ts | ||
| type Options = { | ||
| // format options | ||
| format: ( | ||
| | 'camelCase' | ||
| | 'strictCamelCase' | ||
| | 'PascalCase' | ||
| | 'StrictPascalCase' | ||
| | 'snake_case' | ||
| | 'UPPER_CASE' | ||
| )[]; | ||
| custom?: { | ||
| regex: string; | ||
| match: boolean; | ||
| }; | ||
| leadingUnderscore?: 'forbid' | 'allow' | 'require'; | ||
| trailingUnderscore?: 'forbid' | 'allow' | 'require'; | ||
| prefix?: string[]; | ||
| suffix?: string[]; | ||
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| // selector options | ||
| selector: Selector; | ||
| filter?: string; | ||
| // the allowed values for these are dependent on the selector - see below | ||
| modifiers?: Modifiers<Selector>[]; | ||
| types?: Types<Selector>[]; | ||
| }[]; | ||
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| // the default config essentially does the same thing as ESLint's camelcase rule | ||
| const defaultOptions: Options = [ | ||
| { | ||
| selector: 'default', | ||
| format: ['camelCase'], | ||
| leadingUnderscore: 'allow', | ||
| trailingUnderscore: 'allow', | ||
| }, | ||
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| { | ||
| selector: 'variable', | ||
| format: ['camelCase', 'UPPER_CASE'], | ||
| leadingUnderscore: 'allow', | ||
| trailingUnderscore: 'allow', | ||
| }, | ||
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| { | ||
| selector: 'typeLike', | ||
| format: ['PascalCase'], | ||
| }, | ||
| ]; | ||
| ``` | ||
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| ### Format Options | ||
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| Every single selector can have the same set of format options. | ||
| When the format of an identifier is checked, it is checked in the following order: | ||
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| 1. validate leading underscore | ||
| 1. validate trailing underscore | ||
| 1. validate prefix | ||
| 1. validate suffix | ||
| 1. validate custom | ||
| 1. validate format | ||
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| At each step, if the identifier matches the option, the matching part will be removed. | ||
| For example, if you provide the following formatting option: `{ leadingUnderscore: 'allow', prefix: ['I'], format: ['StrictPascalCase'] }`, for the identifier `_IMyInterface`, then the following checks will occur: | ||
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| 1. `name = _IMyInterface` | ||
| 1. validate leading underscore - pass | ||
| - Trim leading underscore - `name = IMyInterface` | ||
| 1. validate trailing underscore - no check | ||
| 1. validate prefix - pass | ||
| - Trim prefix - `name = MyInterface` | ||
| 1. validate suffix - no check | ||
| 1. validate format - pass | ||
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| One final note is that if the name were to become empty via this trimming process, it is considered to match all `format`s. An example of where this might be useful is for generic type parameters, where you want all names to be prefixed with `T`, but also want to allow for the single character `T` name. | ||
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| #### `format` | ||
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| The `format` option defines the allowed formats for the identifier. This option accepts an array of the following values, and the identifier can match any of them: | ||
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| - `camelCase` - standard camelCase format - no underscores are allowed between characters, and consecutive capitals are allowed (i.e. both `myID` and `myId` are valid). | ||
| - `strictCamelCase` - same as `camelCase`, but consecutive capitals are not allowed (i.e. `myId` is valid, but `myID` is not). | ||
| - `PascalCase` - same as `camelCase`, except the first character must be upper-case. | ||
| - `StrictPascalCase` - same as `strictCamelCase`, except the first character must be upper-case. | ||
| - `snake_case` - standard snake_case format - all characters must be lower-case, and underscores are allowed. | ||
| - `UPPER_CASE` - same as `snake_case`, except all characters must be upper-case. | ||
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| ### `custom` | ||
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| The `custom` option defines a custom regex that the identifier must (or must not) match. This option allows you to have a bit more finer-grained control over identifiers, letting you ban (or force) certain patterns and substrings. | ||
| Accepts an object with the following properties: | ||
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| - `regex` - accepts a regular expression (anything accepted into `new RegExp(filter)`). | ||
| - `match` - true if the identifier _must_ match the `regex`, false if the identifier _must not_ match the `regex`. | ||
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| #### `leadingUnderscore` / `trailingUnderscore` | ||
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| The `leadingUnderscore` / `trailingUnderscore` options control whether leading/trailing underscores are considered valid. Accepts one of the following values: | ||
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| - `forbid` - a leading/trailing underscore is not allowed at all. | ||
| - `allow` - existence of a leading/trailing underscore is not explicitly enforced. | ||
| - `require` - a leading/trailing underscore must be included. | ||
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| #### `prefix` / `suffix` | ||
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| The `prefix` / `suffix` options control which prefix/suffix strings must exist for the identifier. Accepts an array of strings. | ||
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| If these are provided, the identifier must start with one of the provided values. For example, if you provide `{ prefix: ['IFace', 'Class', 'Type'] }`, then the following names are valid: `IFaceFoo`, `ClassBar`, `TypeBaz`, but the name `Bang` is not valid, as it contains none of the prefixes. | ||
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| ### Selector Options | ||
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| - `selector` (see "Allowed Selectors, Modifiers and Types" below). | ||
| - `filter` accepts a regular expression (anything accepted into `new RegExp(filter)`). It allows you to limit the scope of this configuration to names that match this regex. | ||
| - `modifiers` allows you to specify which modifiers to granularly apply to, such as the accessibility (`private`/`public`/`protected`), or if the thing is `static`, etc. | ||
| - The name must match _all_ of the modifiers. | ||
| - For example, if you provide `{ modifiers: ['private', 'static', 'readonly'] }`, then it will only match something that is `private static readonly`, and something that is just `private` will not match. | ||
| - `types` allows you to specify which types to match. This option supports simple, primitive types only (`boolean`, `string`, `number`, `array`, `function`). | ||
| - The name must match _one_ of the types. | ||
| - **_NOTE - Using this option will require that you lint with type information._** | ||
| - For example, this lets you do things like enforce that `boolean` variables are prefixed with a verb. | ||
| - `boolean` matches any type assignable to `boolean | null | undefined` | ||
| - `string` matches any type assignable to `string | null | undefined` | ||
| - `number` matches any type assignable to `number | null | undefined` | ||
| - `array` matches any type assignable to `Array<unknown> | null | undefined` | ||
| - `function` matches any type assignable to `Function | null | undefined` | ||
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| The ordering of selectors does not matter. The implementation will automatically sort the selectors to ensure they match from most-specific to least specific. It will keep checking selectors in that order until it finds one that matches the name. | ||
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| For example, if you provide the following config: | ||
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| ```ts | ||
| [ | ||
| /* 1 */ { selector: 'default', format: ['camelCase'] }, | ||
| /* 2 */ { selector: 'variable', format: ['snake_case'] }, | ||
| /* 3 */ { selector: 'variable', type: ['boolean'], format: ['UPPER_CASE'] }, | ||
| /* 4 */ { selector: 'variableLike', format: ['PascalCase'] }, | ||
| ]; | ||
| ``` | ||
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| Then for the code `const x = 1`, the rule will validate the selectors in the following order: `3`, `2`, `4`, `1`. | ||
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| #### Allowed Selectors, Modifiers and Types | ||
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| There are two types of selectors, individual selectors, and grouped selectors. | ||
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| ##### Individual Selectors | ||
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| Individual Selectors match specific, well-defined sets. There is no overlap between each of the individual selectors. | ||
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| - `variable` - matches any `var` / `let` / `const` variable name. | ||
| - Allowed `modifiers`: none. | ||
| - Allowed `types`: `boolean`, `string`, `number`, `function`, `array`. | ||
| - `function` - matches any named function declaration or named function expression. | ||
| - Allowed `modifiers`: none. | ||
| - Allowed `types`: none. | ||
| - `parameter` - matches any function parameter. Does not match parameter properties. | ||
| - Allowed `modifiers`: none. | ||
| - Allowed `types`: `boolean`, `string`, `number`, `function`, `array`. | ||
| - `property` - matches any object, class, or object type property. Does not match properties that have direct function expression or arrow function expression values. | ||
| - Allowed `modifiers`: `private`, `protected`, `public`, `static`, `readonly`, `abstract`. | ||
| - Allowed `types`: `boolean`, `string`, `number`, `function`, `array`. | ||
| - `parameterProperty` - matches any parameter property. | ||
| - Allowed `modifiers`: `private`, `protected`, `public`, `readonly`. | ||
| - Allowed `types`: `boolean`, `string`, `number`, `function`, `array`. | ||
| - `method` - matches any object, class, or object type method. Also matches properties that have direct function expression or arrow function expression values. Does not match accessors. | ||
| - Allowed `modifiers`: `private`, `protected`, `public`, `static`, `readonly`, `abstract`. | ||
| - Allowed `types`: none. | ||
| - `accessor` - matches any accessor. | ||
| - Allowed `modifiers`: `private`, `protected`, `public`, `static`, `readonly`, `abstract`. | ||
| - Allowed `types`: `boolean`, `string`, `number`, `function`, `array`. | ||
| - `enumMember` - matches any enum member. | ||
| - Allowed `modifiers`: none. | ||
| - Allowed `types`: none. | ||
| - `class` - matches any class declaration. | ||
| - Allowed `modifiers`: `abstract`. | ||
| - Allowed `types`: none. | ||
| - `interface` - matches any interface declaration. | ||
| - Allowed `modifiers`: none. | ||
| - Allowed `types`: none. | ||
| - `typeAlias` - matches any type alias declaration. | ||
| - Allowed `modifiers`: none. | ||
| - Allowed `types`: none. | ||
| - `enum` - matches any enum declaration. | ||
| - Allowed `modifiers`: none. | ||
| - Allowed `types`: none. | ||
| - `typeParameter` - matches any generic type parameter declaration. | ||
| - Allowed `modifiers`: none. | ||
| - Allowed `types`: none. | ||
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| ##### Group Selectors | ||
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| Group Selectors are provided for convenience, and essentially bundle up sets of individual selectors. | ||
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| - `default` - matches everything. | ||
| - Allowed `modifiers`: `private`, `protected`, `public`, `static`, `readonly`, `abstract`. | ||
| - Allowed `types`: none. | ||
| - `variableLike` - matches the same as `variable`, `function` and `parameter`. | ||
| - Allowed `modifiers`: none. | ||
| - Allowed `types`: none. | ||
| - `memberLike` - matches the same as `property`, `parameterProperty`, `method`, `accessor`, `enumMember`. | ||
| - Allowed `modifiers`: `private`, `protected`, `public`, `static`, `readonly`, `abstract`. | ||
| - Allowed `types`: none. | ||
| - `typeLike` - matches the same as `class`, `interface`, `typeAlias`, `enum`, `typeParameter`. | ||
| - Allowed `modifiers`: `abstract`. | ||
| - Allowed `types`: none. | ||
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| ## Examples | ||
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| ### Enforce that all variables, functions and properties follow are camelCase | ||
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| ```json | ||
| { | ||
| "@typescript-eslint/naming-conventions": [ | ||
| "error", | ||
| { "selector": "variableLike", "format": ["camelCase"] } | ||
| ] | ||
| } | ||
| ``` | ||
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| ### Enforce that private members are prefixed with an underscore | ||
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| ```json | ||
| { | ||
| "@typescript-eslint/naming-conventions": [ | ||
| "error", | ||
| { | ||
| "selector": "memberLike", | ||
| "modifier": ["private"], | ||
| "format": ["camelCase"], | ||
| "leadingUnderscore": "require" | ||
| } | ||
| ] | ||
| } | ||
| ``` | ||
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| ### Enforce that boolean variables are prefixed with an allowed verb | ||
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| ```json | ||
| { | ||
| "@typescript-eslint/naming-conventions": [ | ||
| "error", | ||
| { | ||
| "selector": "variable", | ||
| "types": ["boolean"], | ||
| "format": ["PascalCase"], | ||
| "prefix": ["is", "should", "has", "can", "did", "will"] | ||
| } | ||
| ] | ||
| } | ||
| ``` | ||
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| ### Enforce that all variables are either in camelCase or UPPER_CASE | ||
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| ```json | ||
| { | ||
| "@typescript-eslint/naming-conventions": [ | ||
| "error", | ||
| { | ||
| "selector": "variable", | ||
| "format": ["camelCase", "UPPER_CASE"] | ||
| } | ||
| ] | ||
| } | ||
| ``` | ||
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| ### Enforce that type parameters (generics) are prefixed with `T` | ||
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| ```json | ||
| { | ||
| "@typescript-eslint/naming-conventions": [ | ||
| "error", | ||
| { | ||
| "selector": "typeParameter", | ||
| "format": ["PascalCase"], | ||
| "prefix": ["T"] | ||
| } | ||
| ] | ||
| } | ||
| ``` | ||
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| ### Enforce the codebase follows ESLint's `camelcase` conventions | ||
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| ```json | ||
| { | ||
| "@typescript-eslint/naming-conventions": [ | ||
| "error", | ||
| { | ||
| "selector": "default", | ||
| "format": ["camelCase"] | ||
| }, | ||
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| { | ||
| "selector": "variable", | ||
| "format": ["camelCase", "UPPER_CASE"] | ||
| }, | ||
| { | ||
| "selector": "parameter", | ||
| "format": ["camelCase"], | ||
| "leadingUnderscore": "allow" | ||
| }, | ||
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| { | ||
| "selector": "memberLike", | ||
| "modifiers": ["private"], | ||
| "format": ["camelCase"], | ||
| "leadingUnderscore": "require" | ||
| }, | ||
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| { | ||
| "selector": "typeLike", | ||
| "format": ["PascalCase"] | ||
| } | ||
| ] | ||
| } | ||
| ``` | ||
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| ## When Not To Use It | ||
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| If you do not want to enforce naming conventions for anything. |
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