Canonical linting rules for ESLint.
npm install eslint-plugin-canonical
ESLint rules for Canonical ruleset.
``bash`
npm install eslint --save-dev
npm install @typescript-eslint/parser --save-dev
npm install eslint-plugin-canonical --save-dev
1. Set parser property to @typescript-eslint/parser.plugins
1. Add section and specify eslint-plugin-canonical as a plugin.
1. Enable rules.
`json`
{
"parser": "@typescript-eslint/parser",
"plugins": [
"canonical"
],
"rules": {
"canonical/filename-match-exported": 0,
"canonical/filename-match-regex": 0,
"canonical/filename-no-index": 0,
"canonical/id-match": [
2,
"(^[A-Za-z]+(?:[A-Z][a-z])\\d$)|(^[A-Z]+(_[A-Z]+)(_\\d$)*$)|(^(_|\\$)$)",
{
"ignoreDestructuring": true,
"ignoreNamedImports": true,
"onlyDeclarations": true,
"properties": true
}
],
"canonical/no-restricted-strings": 0,
"canonical/no-use-extend-native": 2,
"canonical/prefer-inline-type-import": 2,
"canonical/sort-keys": [
2,
"asc",
{
"caseSensitive": false,
"natural": true
}
]
}
}
This plugin exports a recommended configuration that enforces Canonical type good practices.
To enable this configuration use the extends property in your .eslintrc config file:
`json`
{
"extends": [
"plugin:canonical/recommended"
],
"plugins": [
"canonical"
]
}
See ESLint documentation for more information about extending configuration files.
Like object-property-newline, but for destructuring.
📖 Examples
The following patterns are considered problems:
`js
const {a,b} = obj;
// Message: undefined
const [a,b] = obj;
// Message: undefined
const {a,b,c} = obj;
// Message: undefined
// Message: undefined
const {
a,b} = obj;
// Message: undefined
({a,b}) => {};
// Message: undefined
`
The following patterns are not considered problems:
`js
const {a,
b} = obj;
// Options: [{"allowAllPropertiesOnSameLine":true}]
const {a,b} = obj;
// Options: [{"allowAllPropertiesOnSameLine":true}]
const [a,b] = obj;
const {a} = obj;
const {
a
} = obj;
({a,
b}) => {};
const [a,,b] = obj;
`
Forces every export specifier to be on a new line.
Tip: Combine this rule with object-curly-newline to have every specifier on its own line.
`json`
"object-curly-newline": [
2,
{
"ExportDeclaration": "always"
}
],
Working together, both rules will produces exports such as:
`ts`
export {
a,
b,
c
};
📖 Examples
The following patterns are considered problems:
`js
const a = 1; const b = 2; const c = 3; export { a, b, c };
// Message: undefined
// Message: undefined
const a = 1; const b = 2; const c = 3; export { a, b, c, };
// Message: undefined
// Message: undefined
const a = 1; const b = 2; export { a as default, b }
// Message: undefined
`
The following patterns are not considered problems:
`js
export {
a,
b,
c
} from 'foo'
const a = 1; const b = 2; const c = 3; export {
a,
b,
c
};
export * from 'foo'
`
Match the file name against the default exported value in the module. Files that don't have a default export will be ignored. The exports of index.js are matched against their parent directory.
`js
// Considered problem only if the file isn't named foo.js or foo/index.js
export default function foo() {}
// Considered problem only if the file isn't named Foo.js or Foo/index.js
module.exports = class Foo() {}
// Considered problem only if the file isn't named someVariable.js or someVariable/index.js
module.exports = someVariable;
// Never considered a problem
export default { foo: "bar" };
`
If your filename policy doesn't quite match with your variable naming policy, you can add one or multiple transforms:
`json`
"canonical/filename-match-exported": [ 2, { "transforms": "kebab" } ]
Now, in your code:
`js`
// Considered problem only if file isn't named variable-name.js or variable-name/index.js
export default function variableName;
Available transforms:
* snake
*
*
*
For multiple transforms simply specify an array like this (null in this case stands for no transform):
`json`
"canonical/filename-match-exported": [2, { "transforms": [ null, "kebab", "snake" ] } ]
If you prefer to use suffixes for your files (e.g. Foo.react.js for a React component file), you can use a second configuration parameter. It allows you to remove parts of a filename matching a regex pattern before transforming and matching against the export.
`json`
"canonical/filename-match-exported": [ 2, { "suffix": "\\.react$" } ]
Now, in your code:
`js`
// Considered problem only if file isn't named variableName.react.js, variableName.js or variableName/index.js
export default function variableName;
If you also want to match exported function calls you can use the third option (a boolean flag).
`json`
"canonical/filename-match-exported": [ 2, { "matchCallExpression": true } ]
Now, in your code:
`js`
// Considered problem only if file isn't named functionName.js or functionName/index.js
export default functionName();
📖 Examples
The following patterns are considered problems:
`js
module.exports = exported;
// Message: undefined
module.exports = class Foo {};
// Message: undefined
module.exports = class Foo { render() { return Test Class; } };
// Message: undefined
module.exports = function foo() {};
// Message: undefined
module.exports = function foo() { return Test Fn };
// Message: undefined
export default exported;
// Message: undefined
export default class Foo {};
// Message: undefined
export default class Foo { render() { return Test Class; } };
// Message: undefined
export default function foo() {};
// Message: undefined
export default function foo() { return Test Fn };
// Message: undefined
module.exports = exported;
// Message: undefined
module.exports = class Foo { render() { return Test Class; } };
// Message: undefined
// Options: [{"transforms":"snake"}]
module.exports = variableName;
// Message: undefined
// Options: [{"transforms":"kebab"}]
export default variableName;
// Message: undefined
// Options: [{"transforms":"pascal"}]
export default variableName;
// Message: undefined
// Options: [{"transforms":["pascal","snake"]}]
export default variableName;
// Message: undefined
// Options: [{"suffix":"\\.react$"}]
export default class Foo { render() { return Test Class; } };
// Message: undefined
// Options: [{"suffix":"\\.react$"}]
export default class Foo { render() { return Test Class; } };
// Message: undefined
// Options: [{"matchCallExpression":true}]
module.exports = foo();
// Message: undefined
`
The following patterns are not considered problems:
`js
module.exports = function() {};
var foo = 'bar';
export default foo();
module.exports = exported;
module.exports = class Foo {};
module.exports = class Foo { render() { return Test Class; } };
module.exports = function foo() {};
module.exports = foo();
module.exports = function foo() { return Test Fn };
export default exported;
export default class Foo {};
export default class Foo { render() { return Test Class; } };
export default function foo() {};
export default function foo() { return Test Fn };
export default function foo() {};
export default function foo() { return Test Fn };
export default function index() {};
// Options: [{"transforms":"snake"}]
module.exports = variableName;
// Options: [{"transforms":"snake"}]
module.exports = variableName;
// Options: [{"transforms":"kebab"}]
module.exports = variableName;
// Options: [{"transforms":"camel"}]
module.exports = variable_name;
// Options: [{"transforms":"snake"}]
export default variableName;
// Options: [{"transforms":"kebab"}]
export default variableName;
// Options: [{"transforms":"camel"}]
export default variable_name;
// Options: [{"transforms":"pascal"}]
export default variable_name;
// Options: [{"transforms":["pascal","camel"]}]
export default variable_name;
// Options: [{"transforms":["pascal","camel"]}]
export default variable_name;
// Options: [{"suffix":"\\.react$"}]
module.exports = class Foo { render() { return Test Class; } };
// Options: [{"suffix":"\\.react$"}]
export default class Foo { render() { return Test Class; } };
// Options: [{"matchCallExpression":true}]
module.exports = foo();
`
Enforce a certain file naming convention using a regular expression.
The convention can be configured using a regular expression (the default is camelCase.js). Additionally
exporting files can be ignored with a second configuration parameter.
`json`
"canonical/filename-match-regex": [2, { "regex": "^[a-z_]+$", "ignoreExporting": true }]
With these configuration options, camelCase.js will be reported as an error while snake_case.js will pass.match-exported
Additionally the files that have a named default export (according to the logic in the rule) will bematch-exported
ignored. They could be linted with the rule. Please note that exported function calls are not
respected in this case.
📖 Examples
The following patterns are considered problems:
`js
var foo = 'bar';
// Message: undefined
var foo = 'bar';
// Message: undefined
var foo = 'bar';
// Message: undefined
// Options: [{"regex":"^[a-z_]$"}]
var foo = 'bar';
// Message: undefined
`
The following patterns are not considered problems:
`js
var foo = 'bar';
var foo = 'bar';
var foo = 'bar';
// Options: [{"regex":"^[a-z_]+$"}]
var foo = 'bar';
// Options: [{"regex":"^[a-z_]+$"}]
var foo = 'bar';
var foo = 'bar';
// Options: [{"ignoreExporting":true}]
module.exports = foo
// Options: [{"ignoreExporting":true,"regex":"^[a-z_]$"}]
module.exports = foo
// Options: [{"ignoreExporting":true,"regex":"^[a-z_]+$"}]
module.exports = foo()
`
Having a bunch of index.js files can have negative influence on developer experience, e.g. whenindex.js
opening files by name. When enabling this rule. files will always be considered a problem.
📖 Examples
The following patterns are considered problems:
`js
var foo = 'bar';
// Message: undefined
var foo = 'bar';
// Message: undefined
`
The following patterns are not considered problems:
`js
var foo = 'bar';
var foo = 'bar';
var foo = 'bar';
var foo = 'bar';
`
_The --fix option on the command line automatically fixes problems reported by this rule._
Note: This rule is equivalent to id-match, except for addition of ignoreNamedImports.
This rule requires identifiers in assignments and function definitions to match a specified regular expression.
* "properties": false (default) does not check object properties"properties": true
* requires object literal properties and member expression assignment properties to match the specified regular expression"classFields": false
* (default) does not class field names"classFields": true
* requires class field names to match the specified regular expression"onlyDeclarations": false
* (default) requires all variable names to match the specified regular expression"onlyDeclarations": true
* requires only var, function, and class declarations to match the specified regular expression"ignoreDestructuring": false
* (default) enforces id-match for destructured identifiers"ignoreDestructuring": true
* does not check destructured identifiers"ignoreNamedImports": false
* (default) enforces id-match for named imports"ignoreNamedImports": true
* does not check named imports
📖 Examples
The following patterns are considered problems:
`js
// Options: ["^[a-z]+$",{"onlyDeclarations":true}]
var __foo = "Matthieu"
// Message: undefined
// Options: ["^[a-z]+$"]
first_name = "Matthieu"
// Message: undefined
// Options: ["^z"]
first_name = "Matthieu"
// Message: undefined
// Options: ["^[a-z]+(_[A-Z][a-z])*$"]
Last_Name = "Larcher"
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
var obj = {key: no_under}
// Message: undefined
// Options: ["^[^_]+$"]
function no_under21(){}
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
obj.no_under22 = function(){};
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
no_under23.foo = function(){};
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
[no_under24.baz]
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
if (foo.bar_baz === boom.bam_pow) { [no_under25.baz] }
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
foo.no_under26 = boom.bam_pow
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
var foo = { no_under27: boom.bam_pow }
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
foo.qux.no_under28 = { bar: boom.bam_pow }
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
var o = {no_under29: 1}
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
obj.no_under30 = 2;
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
var { category_id: category_alias } = query;
// Message: undefined
// Options: ["^[^_]+$",{"ignoreDestructuring":true,"properties":true}]
var { category_id: category_alias } = query;
// Message: undefined
// Options: ["^[^_]+$",{"ignoreDestructuring":true,"properties":true}]
var { category_id: categoryId, ...other_props } = query;
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
var { category_id } = query;
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
var { category_id = 1 } = query;
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
import no_camelcased from "external-module";
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
import * as no_camelcased from "external-module";
// Message: undefined
// Options: ["^[^_]+$"]
export * as no_camelcased from "external-module";
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
import { no_camelcased as no_camel_cased } from "external module";
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
import { camelCased as no_camel_cased } from "external module";
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
import { camelCased, no_camelcased } from "external-module";
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
import { no_camelcased as camelCased, another_no_camelcased } from "external-module";
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
import camelCased, { no_camelcased } from "external-module";
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
import no_camelcased, { another_no_camelcased as camelCased } from "external-module";
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
function foo({ no_camelcased }) {};
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
function foo({ no_camelcased = 'default value' }) {};
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
const no_camelcased = 0; function foo({ camelcased_value = no_camelcased }) {}
// Message: undefined
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
const { bar: no_camelcased } = foo;
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
function foo({ value_1: my_default }) {}
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
function foo({ isCamelcased: no_camelcased }) {};
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
var { foo: bar_baz = 1 } = quz;
// Message: undefined
// Options: ["^[^_]+$",{"properties":true}]
const { no_camelcased = false } = bar;
// Message: undefined
// Options: ["^[^_]+$"]
class x { _foo() {} }
// Message: undefined
// Options: ["^[^_]+$",{"classFields":true}]
class x { _foo = 1; }
// Message: undefined
// Options: ["^[^_]+$",{"ignoreNamedImports":false}]
import { no_camelcased } from "external-module";
// Message: undefined
`
The following patterns are not considered problems:
`js
// Options: ["^[a-z]+$",{"onlyDeclarations":true}]
__foo = "Matthieu"
// Options: ["^[a-z]+$"]
firstname = "Matthieu"
// Options: ["[a-z]+"]
first_name = "Matthieu"
// Options: ["^f"]
firstname = "Matthieu"
// Options: ["^[a-z]+(_[A-Z][a-z]+)*$"]
last_Name = "Larcher"
// Options: ["^[a-z]+(_[A-Z][a-z])*$"]
param = "none"
// Options: ["^[^_]+$"]
function noUnder(){}
// Options: ["^[^_]+$"]
no_under()
// Options: ["^[^_]+$"]
foo.no_under2()
// Options: ["^[^_]+$"]
var foo = bar.no_under3;
// Options: ["^[^_]+$"]
var foo = bar.no_under4.something;
// Options: ["^[^_]+$"]
foo.no_under5.qux = bar.no_under6.something;
// Options: ["^[^_]+$"]
if (bar.no_under7) {}
// Options: ["^[^_]+$"]
var obj = { key: foo.no_under8 };
// Options: ["^[^_]+$"]
var arr = [foo.no_under9];
// Options: ["^[^_]+$"]
[foo.no_under10]
// Options: ["^[^_]+$"]
var arr = [foo.no_under11.qux];
// Options: ["^[^_]+$"]
[foo.no_under12.nesting]
// Options: ["^[^_]+$"]
if (foo.no_under13 === boom.no_under14) { [foo.no_under15] }
// Options: ["^[a-z$]+([A-Z][a-z]+)*$"]
var myArray = new Array(); var myDate = new Date();
// Options: ["^[^_]+$"]
var x = obj._foo;
// Options: ["^[^_]+$",{"onlyDeclarations":true,"properties":true}]
var obj = {key: no_under}
// Options: ["^[^_]+$",{"properties":true}]
var {key_no_under: key} = {}
// Options: ["^[^_]+$",{"ignoreDestructuring":true,"properties":true}]
var { category_id } = query;
// Options: ["^[^_]+$",{"ignoreDestructuring":true,"properties":true}]
var { category_id: category_id } = query;
// Options: ["^[^_]+$",{"ignoreDestructuring":true,"properties":true}]
var { category_id = 1 } = query;
// Options: ["^[^_]+$",{"properties":true}]
var o = {key: 1}
// Options: ["^[^_]+$",{"properties":false}]
var o = {no_under16: 1}
// Options: ["^[^_]+$",{"properties":false}]
obj.no_under17 = 2;
// Options: ["^[^_]+$",{"properties":false}]
var obj = {
no_under18: 1
};
obj.no_under19 = 2;
// Options: ["^[^_]+$",{"properties":false}]
obj.no_under20 = function(){};
// Options: ["^[^_]+$",{"properties":false}]
var x = obj._foo2;
// Options: ["^[^_]+$"]
class x { foo() {} }
// Options: ["^[^_]+$"]
class x { #foo() {} }
// Options: ["^[^_]+$",{"ignoreNamedImports":true}]
import { no_camelcased } from "external-module";
// Options: ["^[a-zA-Z\\d]+$"]
const {
index,
'0': n0,
'1': n1,
} = exampleCode;
`
Forces every import specifier to be on a new line.
Tip: Combine this rule with object-curly-newline to have every specifier on its own line.
`json`
"object-curly-newline": [
2,
{
"ImportDeclaration": "always"
}
],
Working together, both rules will produces imports such as:
`ts`
import {
a,
b,
c
} from 'foo';
📖 Examples
The following patterns are considered problems:
`js
import {a, b} from 'foo';
// Message: undefined
import a, {b, c} from 'foo';
// Message: undefined
`
The following patterns are not considered problems:
`js
import {a,
b} from 'foo'
import a, {b,
c} from 'foo'
`
_The --fix option on the command line automatically fixes problems reported by this rule._
Requires that resources are imported from the same files in which they are defined.
This rule converts the following:
`ts`
// foo.ts
import { bar } from './bar';
// bar.ts
export { baz as bar } from './baz';
// baz.ts
export const baz = 'BAZ';
to:
`ts`
// foo.ts
import { baz as bar } from './baz';
// baz.ts
export const baz = 'BAZ';
This rule handles
* named imports
* default imports
* aliased imports
You must configure import/parsers and import/resolver for this rule to work, e.g.
`ts`
settings: {
'import/parsers': {
'@typescript-eslint/parser': ['.ts', '.tsx'],
},
'import/resolver': {
typescript: {
project: path.resolve(
__dirname,
'tsconfig.json',
),
},
},
},
📖 Examples
The following patterns are considered problems:
`js
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
import { foo } from './bar';
// Message: undefined
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
import { foo as FOO } from './bar';
// Message: undefined
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
import { bar } from './bar';
// Message: undefined
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
import { foo } from './baz';
// Message: undefined
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
import foo from './bar';
// Message: undefined
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
import { type Foo } from './bar';
// Message: undefined
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
import { foo, bar } from './bar';
// Message: undefined
`
The following patterns are not considered problems:
`js
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
import { foo } from './foo';
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
import foo from './foo';
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
import { logLevels } from 'roarr';
`
_The --fix option on the command line automatically fixes problems reported by this rule._
Requite that re-exports are named.
📖 Examples
The following patterns are considered problems:
`js
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
export * from './foo';
// Message: undefined
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
export * from './foo';
// Message: undefined
`
The following patterns are not considered problems:
`js
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
export { FOO } from './foo';
// Settings: {"import/parsers":{"@typescript-eslint/parser":[".ts",".tsx"]},"import/resolver":{"typescript":{"project":"
export * as foo from './foo';
`
Disallows the practice of importing an entire module's namespace using import * as Namespace and then destructuring specific exports from it. Instead, it encourages direct importing of only the necessary named exports from a module.
📖 Examples
The following patterns are considered problems:
`js`
import * as bar from 'bar'; const { foo } = bar;
// Message: undefined
The following patterns are not considered problems:
`js`
import * as bar from 'bar'
Disallows re-exports of imports.
📖 Examples
The following patterns are considered problems:
`js
import Button1 from 'app/CustomButton';
export const CustomButton = Button1;
// Message: undefined
import { Button as CustomButton2 } from 'app/CustomButton';
export const CustomButton = CustomButton2;
// Message: undefined
import * as Button3 from "app/Button";
export const CustomButton = Button3;
// Message: undefined
import Button4 from 'app/CustomButton';
export default Button4;
// Message: undefined
export { default as Button5 } from 'app/CustomButton';
// Message: undefined
import Button6 from 'app/CustomButton';
export {
Button6
};
// Message: undefined
import Button7 from 'app/CustomButton';
export const Buttons = {
Button: Button7
};
// Message: undefined
import Button8 from 'app/CustomButton';
export default Button8;
export { Button8 }
// Message: undefined
// Message: undefined
export * from 'app/CustomButton';
// Message: undefined
`
> [!NOTE]
> This rule was originally developed by @christianvuerings as part of https://github.com/christianvuerings/eslint-plugin-no-re-export
Restricts re-assigning imports to variables that are exported.
📖 Examples
The following patterns are considered problems:
`js
import { Foo } from './Foo';
export const Bar = {
Foo,
};
// Message: undefined
import { Foo } from './Foo';
export default {
Foo,
};
// Message: undefined
`
Disallow specified modules when loaded by import
This rule is similar to no-restricted-imports except that it allows you to specify unique messages for each restricted import (a workaround for issue issues#15261).
> Note: Unlike the ESLint rule, this rule does not support the patterns option and it does not handle exports.
📖 Examples
The following patterns are considered problems:
`js
// Options: [{"paths":[{"importName":"*","message":"foo is restricted","name":"bar"}]}]
import * as bar from 'bar'
// Message: undefined
// Options: [{"paths":[{"importName":"foo","message":"foo is restricted","name":"bar"}]}]
import { foo } from 'bar'
// Message: undefined
// Options: [{"paths":[{"importName":"default","message":"foo is restricted","name":"bar"}]}]
import { default as bar } from 'bar'
// Message: undefined
// Options: [{"paths":[{"message":"foo is restricted","name":"bar"}]}]
import bar from 'bar'
// Message: undefined
`
The following patterns are not considered problems:
`js`
// Options: [{"paths":[{"importName":"foo","message":"foo is restricted","name":"bar"}]}]
import { bar } from 'bar'
Disallow specified strings.
📖 Examples
The following patterns are considered problems:
`js
// Options: [["bar"]]
var foo = "bar"
// Message: undefined
// Options: [["bar"]]
const foo = bar ${baz};`
// Message: undefined
The following patterns are not considered problems:
`js`
const foo = "bar";
The 1st option is an array of strings that cannot be contained in the codebase.
📖 Examples
The following patterns are considered problems:
`js
Array.prototype.custom
// Message: undefined
Array.to
// Message: undefined
Array.to()
// Message: undefined
[].length()
// Message: undefined
'unicorn'.green
// Message: undefined
[].custom()
// Message: undefined
({}).custom()
// Message: undefined
/match_this/.custom()
// Message: undefined
'string'.custom()
// Message: undefined
console.log('foo'.custom)
// Message: undefined
console.log('foo'.custom())
// Message: undefined
('str' + 'ing').custom()
// Message: undefined
('str' + 'i' + 'ng').custom()
// Message: undefined
(1 + 'ing').custom()
// Message: undefined
(/regex/ + 'ing').custom()
// Message: undefined
(1 + 1).toLowerCase()
// Message: undefined
(1 + 1 + 1).toLowerCase()
// Message: undefined
(function testFunction() {}).custom()
// Message: undefined
new Array().custom()
// Message: undefined
new ArrayBuffer().custom()
// Message: undefined
new Boolean().custom()
// Message: undefined
new DataView().custom()
// Message: undefined
new Date().custom()
// Message: undefined
new Error().custom()
// Message: undefined
new Float32Array().custom()
// Message: undefined
new Float64Array().custom()
// Message: undefined
new Function().custom()
// Message: undefined
new Int16Array().custom()
// Message: undefined
new Int32Array().custom()
// Message: undefined
new Int8Array().custom()
// Message: undefined
new Map().custom()
// Message: undefined
new Number().custom()
// Message: undefined
new Object().custom()
// Message: undefined
new Promise().custom()
// Message: undefined
new RegExp().custom()
// Message: undefined
new Set().custom()
// Message: undefined
new String().custom()
// Message: undefined
new Symbol().custom()
// Message: undefined
new Uint16Array().custom()
// Message: undefined
new Uint32Array().custom()
// Message: undefined
new Uint8Array().custom()
// Message: undefined
new Uint8ClampedArray().custom()
// Message: undefined
new WeakMap().custom()
// Message: undefined
new WeakSet().custom()
// Message: undefined
new Array()['custom']
// Message: undefined
new Array()['custom']()
// Message: undefined
`
The following patterns are not considered problems:
`js
error.plugin
error.plugn()
array.custom
Object.groupBy()
Object.assign()
Object.keys
Object.keys()
gulp.task()
Custom.prototype.custom
Array.prototype.map
Array.prototype.map.call([1,2,3], function (x) { console.log(x) })
Array.apply
Array.call(null, 1, 2, 3)
[].push(1)
[][0]
{}[i]
{}[3]
{}[j][k]
({foo: {bar: 1, baz: 2}}[i][j])
({}).toString()
/match_this/.test()
'foo'.length
'hi'.padEnd
'hi'.padEnd()
console.log('foo'.length)
console.log('foo'.toString)
console.log('foo'.toString())
console.log(gulp.task)
console.log(gulp.task())
'string'.toString()
(1).toFixed()
1..toFixed()
1.0.toFixed()
('str' + 'ing').toString()
('str' + 'i' + 'ng').toString()
(1 + 1).valueOf()
(1 + 1 + (1 + 1)).valueOf()
(1 + 1 + 1).valueOf()
(1 + 'string').toString()
(/regex/ + /regex/).toString()
(/regex/ + 1).toString()
([1] + [2]).toString()
(function testFunction() {}).toString()
Test.prototype
new Array().toString()
new ArrayBuffer().constructor()
new Boolean().toString()
new DataView().buffer()
new Date().getDate()
new Error().message()
new Error().stack
new Error().stack.slice(1)
new Float32Array().values()
new Float64Array().values()
new Function().toString()
new Int16Array().values()
new Int32Array().values()
new Int8Array().values()
new Map().clear()
new Number().toString()
new Object().toString()
new Object().toString
new Promise().then()
new RegExp().test()
new Set().values()
new String().toString()
new Symbol().toString()
new Uint16Array().values()
new Uint32Array().values()
new Uint8ClampedArray().values()
new WeakMap().get()
new WeakSet().has()
new Array()['length']
new Array()['toString']()
`
_The --fix option on the command line automatically fixes problems reported by this rule._
Restrict imports to path aliases or relative imports limited by depth.
The same alias can be applied using multiple rules, e.g.
`ts`
'canonical/prefer-import-alias': [
2,
{
aliases: [
{
alias: '@/',
matchParent: path.resolve(__dirname, 'src'),
matchPath: '^src\\/',
},
{
alias: '@/',
matchPath: '^src\\/',
maxRelativeDepth: 2,
},
],
},
],
In this example, we are saying:
* rewrite import path to use alias when
* import path matches ^src\/
* the grandfather directory is
* rewrite import path to use alias when
* import path matches
* relative import is greater than 2
The grandfather directory is essentially whichever directory that is accessed by the doubledot (../) by the import path.
📖 Examples
The following patterns are considered problems:
`js
// Options: [{"aliases":[{"alias":"@/a/","matchPath":"^a\\/","maxRelativeDepth":-1}],"baseDirectory":"
import { bar } from './bar';
// Message: undefined
// Options: [{"aliases":[{"alias":"@/a/","matchPath":"^a\\/","maxRelativeDepth":1}],"baseDirectory":"
import { baz } from '../baz';
// Message: undefined
// Options: [{"aliases":[{"alias":"@/a/","matchPath":"^a\\/"}],"baseDirectory":"
import { bar } from '../bar';
// Message: undefined
`
The following patterns are not considered problems:
`js
// Options: [{"aliases":[{"alias":"@/a/","matchParent":"
import { bar } from '../bar';
// Options: [{"baseDirectory":"
import Foo from '@bar/baz';
// Options: [{"baseDirectory":"
import Foo, { Foo } from 'bar';
// Options: [{"baseDirectory":"
import { foo } from './foo';
// Options: [{"baseDirectory":"
import { foo } from '../foo';
// Options: [{"baseDirectory":"
import { foo } from '.././foo';
// Options: [{"baseDirectory":"
import { foo } from '././../foo';
// Options: [{"baseDirectory":"
import { foo } from '@bar/baz';
// Options: [{"baseDirectory":"
import { foo } from '../../foo';
`
_The --fix option on the command line automatically fixes problems reported by this rule._
TypeScript 4.5 introduced type modifiers that allow to inline type imports as opposed to having dedicated import type. This allows to remove duplicate type imports. This rule enforces use of import type modifiers.
📖 Examples
The following patterns are considered problems:
`js
import type {foo} from 'bar'
// Message: undefined
import type {foo, baz} from 'bar'
// Message: undefined
`
The following patterns are not considered problems:
`js
import {type foo} from 'bar'
import type Foo from 'bar'
import type * as Foo from 'bar'
`
Requires that components that can be loaded lazily be imported using the React.lazy() function.
`tsx
import { lazy } from 'react';
import { Foo } from './Foo';
export default () => {
return Math.random() > 0.5 ?
};
`
This rule converts the above code to:
`tsx
import { lazy } from 'react';
const Foo = lazy(() => import('./Foo.js').then(({ Foo }) => ({ default: Foo })));
export default () => {
return Math.random() > 0.5 ?
};
`
📖 Examples
The following patterns are considered problems:
`js
import React from 'react';
import { Foo } from './Foo';
export default () => {
return <>
{Math.random() > 0.5 ?
;
};
// Message: undefined
import React from 'react';
import { Foo } from './Foo';
export default () => {
return <>
{Math.random() > 0.5 ?
import React from 'react';
import { Foo } from './Foo';
export default () => {
return Math.random() > 0.5 ?
};
// Message: undefined
`
The following patterns are not considered problems:
`js
import React, { lazy } from 'react';
const Foo = lazy(() => import('./Foo').then(({ Foo }) => ({ default: Foo })));
export default () => {
return Math.random() > 0.5 ?
};
`
In React, it is common to use useEffect without dependencies when the intent is to run the effect only once (on mount and unmount). However, just doing that may lead to undesired side-effects, such as the effect being called twice in Strict Mode. For this reason, it is better to use an abstraction such as useMount that handles this use case.
📖 Examples
The following patterns are considered problems:
`js`
useEffect(() => {}, [])
// Message: undefined
The following patterns are not considered problems:
`js
useEffect(() => {}, [foo])
useMount(() => {}, [])
`
_The --fix option on the command line automatically fixes problems reported by this rule._
Adds .js extension to all imports and exports.
It resolves the following cases:
Relative imports that resolve to a file of the same name:
`js`
import './foo'; // => import './foo.js';
Relative imports that resolve to an index file:
`js`
import './foo'; // => import './foo/index.js';
The above examples would also work if the file extension was .ts or .tsx, i.e.
`js`
import './foo'; // => import './foo.ts';
import './foo'; // => import './foo/index.tsx';
For this to work, you have to configure import/resolver:
`ts`
settings: {
'import/resolver': {
typescript: {
project: path.resolve(__dirname, 'tsconfig.json'),
},
},
},
Imports that resolve to a file of the same name:
`js`
import { foo } from '@/foo'; // => import { foo } from '@/foo.js';
Imports that resolve to an index file:
`js`
import { foo } from '@/foo'; // => import { foo } from '@/foo/index.js';
📖 Examples
The following patterns are considered problems:
`js
// Settings: {"import/resolver":{"typescript":{"project":"
import { foo } from '@/foo';
// Message: undefined
// Settings: {"import/resolver":{"typescript":{"project":"
import { foo } from '@/foo';
// Message: undefined
// Settings: {"import/resolver":{"typescript":{"project":"
import { foo } from './foo';
// Message: undefined
// Settings: {"import/resolver":{"typescript":{"project":"
import { foo } from './foo';
// Message: undefined
// Settings: {"import/resolver":{"typescript":{"project":"
export { foo } from './foo';
// Message: undefined
// Settings: {"import/resolver":{"typescript":{"project":"
export * from './foo';
// Message: undefined
`
The following patterns are not considered problems:
`js
// Settings: {"import/resolver":{"typescript":{"project":"
// @ts-expect-error ignore search params
import { foo } from './foo.svg?url';
// Settings: {"import/resolver":{"typescript":{"project":"
import { foo } from '@/foo.css';
// Settings: {"import/resolver":{"typescript":{"project":"
import { foo } from '@/foo.js';
// Settings: {"import/resolver":{"typescript":{"project":"
import { foo } from './foo.css';
// Settings: {"import/resolver":{"typescript":{"project":"
import { foo } from './foo.js';
// Settings: {"import/resolver":{"typescript":{"project":"
// Note that this resolves to roarr, which is a package with TypeScript types.
// Compare this test to the "packageTypesImport" test which imports dependency's types.
import { Roarr } from 'roarr';
// Settings: {"import/resolver":{"typescript":{"project":"
// Note that this resolves to @types/chance, which is a TypeScript declaration file.
// Compare this test to the "typedPackageImport" test which imports a typed dependency.
import { Chance } from 'chance';
`
_The --fix option on the command line automatically fixes problems reported by this rule._
Requires that dependencies of React methods (useEffect, useCallback and useMemo) are sorted alphabetically.
📖 Examples
The following patterns are considered problems:
`js`
useEffect(() => {}, [b, a])
// Message: undefined
The following patterns are not considered problems:
`js`
useEffect(() => {}, [a, b])
This ESLint plugin is written using @typescript-eslint/utils, which assume that @typescript-eslint/parser is used.
Some rules may work without @typescript-eslint/parser. However, rules are implemented and tested assuming that @typescript-eslint/parser` is used.