sort-heritage-clauses

Enforce sorted heritage clauses.

This rule detects instances where heritage clauses are not sorted and raises linting errors, encouraging developers to arrange elements in the desired order.

Try it out

interface Interface extends StartupService, Logged, Pausable {
 // ...
}

class Class implements StartupService, Logged, Pausable {
 // ...
}

Options

This rule accepts an options object with the following properties:

type

_{default: 'alphabetical'}

Specifies the sorting method.

'alphabetical' — Sort items alphabetically (e.g., “a” < “b” < “c”) using localeCompare.
'natural' — Sort items in a natural order (e.g., “item2” < “item10”).
'line-length' — Sort items by code line length (shorter lines first).
'custom' — Sort items using the alphabet specified in the alphabet option.
'unsorted' — Do not sort items. grouping is still enforced.

order

_{default: 'asc'}

Specifies whether to sort items in ascending or descending order.

'asc' — Sort items in ascending order (A to Z, 1 to 9).
'desc' — Sort items in descending order (Z to A, 9 to 1).

fallbackSort

_{type:
{
type: 'alphabetical' | 'natural' | 'line-length' | 'custom' | 'unsorted'
order?: 'asc' | 'desc'
}}_{default: { type: 'unsorted' }}

Specifies fallback sort options for elements that are equal according to the primary sort type.

Example: enforce alphabetical sort between two elements with the same length.

{
  type: 'line-length',
  order: 'desc',
  fallbackSort: { type: 'alphabetical', order: 'asc' }
}

alphabet

_{default: ''}

Used only when the type option is set to 'custom'. Specifies the custom alphabet for sorting.

Use the Alphabet utility class from eslint-plugin-perfectionist/alphabet to quickly generate a custom alphabet.

Example: 0123456789abcdef...

ignoreCase

_{default: true}

Specifies whether sorting should be case-sensitive.

true — Ignore case when sorting alphabetically or naturally (e.g., “A” and “a” are the same).
false — Consider case when sorting (e.g., “a” comes before “A”).

specialCharacters

_{default: keep}

Specifies whether to trim, remove, or keep special characters before sorting.

'keep' — Keep special characters when sorting (e.g., “_a” comes before “a”).
'trim' — Trim special characters when sorting alphabetically or naturally (e.g., “_a” and “a” are the same).
'remove' — Remove special characters when sorting (e.g., “/a/b” and “ab” are the same).

locales

_{default: 'en-US'}

Specifies the sorting locales. Refer To String.prototype.localeCompare() - locales.

string — A BCP 47 language tag (e.g. 'en', 'en-US', 'zh-CN').
string[] — An array of BCP 47 language tags.

partitionByComment

_{default: false}

Enables the use of comments to separate class decorators into logical groups.

true — All comments will be treated as delimiters, creating partitions.
false — Comments will not be used as delimiters.
RegExpPattern = string | { pattern: string; flags: string} — A regexp pattern to specify which comments should act as delimiters.
RegExpPattern[] — A list of regexp patterns to specify which comments should act as delimiters.
{ block: boolean | RegExpPattern | RegExpPattern[]; line: boolean | RegExpPattern | RegExpPattern[] } — Specify which block and line comments should act as delimiters.

partitionByNewLine

_{default: false}

When true, the rule will not sort the heritage clauses if there is an empty line between them.

newlinesBetween

_{type: number | 'ignore'}_{default: 'ignore'}

Specifies how to handle newlines between groups.

'ignore' — Do not report errors related to newlines.
0 — No newlines are allowed.
Any other number — Enforce this number of newlines between each group.

You can also enforce the newline behavior between two specific groups through the groups option.

This option is only applicable when partitionByNewLine is false.

newlinesInside

_{type: number | 'ignore' | 'newlinesBetween'}_{default: 'newlinesBetween'}

Specifies how to handle newlines inside groups.

'ignore' — Do not report errors related to newlines.
'newlinesBetween' — [DEPRECATED] If newlinesBetween is 'ignore', then 'ignore', otherwise 0.
0 — No newlines are allowed.
Any other number — Enforce this number of newlines between each element of the same group.

You can also enforce the newline behavior inside a given group through the groups or customGroups options.

This option is only applicable when partitionByNewLine is false.

groups

_{type:
Array<
| string
| string[]
| { newlinesBetween: number | 'ignore' }
| {
group: string | string[];
type?: 'alphabetical' | 'natural' | 'line-length' | 'custom' | 'unsorted';
order?: 'asc' | 'desc';
newlinesInside?: number | 'ignore';
}
>}_{default: []}

Specifies a list of heritage clause groups for sorting.

Predefined groups:

'unknown' — Heritage Clauses that don’t fit into any group specified in the groups option.

If the unknown group is not specified in the groups option, it will automatically be added to the end of the list.

Each heritage clause will be assigned a single group specified in the groups option (or the unknown group if no match is found). The order of items in the groups option determines how groups are ordered.

Within a given group, members will be sorted according to the type, order, ignoreCase, etc. options.

Individual groups can be combined together by placing them in an array. The order of groups in that array does not matter. All members of the groups in the array will be sorted together as if they were part of a single group.

Group with overridden settings

You may directly override options for a specific group by using an object with the group property and other option overrides.

type — Overrides the type option for that group.
order — Overrides the order option for that group.
fallbackSort — Overrides the fallbackSort option for that group.
newlinesInside — Enforces a specific newline behavior between elements of the group.

{
  groups: [
    'myCustomGroup1',
    { group: 'myCustomGroup2', type: 'unsorted' }, // Elements from this group will not be sorted
  ]
}

Newlines between groups

You may place newlinesBetween objects between your groups to enforce the newline behavior between two specific groups.

See the newlinesBetween option.

This feature is only applicable when partitionByNewLine is false.

{
  newlinesBetween: 1,
  groups: [
    'a',
    { newlinesBetween: 0 }, // Overrides the global newlinesBetween option
    'b',
  ]
}

customGroups

Migrating from the old API

Support for the object-based customGroups option has been removed.

Migrating from the old to the current API is easy:

Old API:

{
  "key1": "value1",
  "key2": "value2"
}

Current API:

[
  {
    "groupName": "key1",
    "elementNamePattern": "value1"
  },
  {
    "groupName": "key2",
    "elementNamePattern": "value2"
  }
]

_{type: Array<CustomGroupDefinition | CustomGroupAnyOfDefinition>}_{default: []}

Defines custom groups to match specific heritage clauses.

A custom group definition may follow one of the two following interfaces:

interface CustomGroupDefinition {
  groupName: string
  type?: 'alphabetical' | 'natural' | 'line-length' | 'unsorted'
  order?: 'asc' | 'desc'
  fallbackSort?: { type: string; order?: 'asc' | 'desc' }
  newlinesInside?: number | 'ignore'
  elementNamePattern?: string | string[] | { pattern: string; flags?: string } | { pattern: string; flags?: string }[]
}

A declaration will match a CustomGroupDefinition group if it matches all the filters of the custom group’s definition.

or:

interface CustomGroupAnyOfDefinition {
  groupName: string
  type?: 'alphabetical' | 'natural' | 'line-length' | 'unsorted'
  order?: 'asc' | 'desc'
  fallbackSort?: { type: string; order?: 'asc' | 'desc' }
  newlinesInside?: number | 'ignore'
  anyOf: Array<{
      selector?: string
      elementNamePattern?: string | string[] | { pattern: string; flags?: string } | { pattern: string; flags?: string }[]
  }>
}

A declaration will match a CustomGroupAnyOfDefinition group if it matches all the filters of at least one of the anyOf items.

Attributes

groupName — The group’s name, which needs to be put in the groups option.
elementNamePattern — If entered, will check that the name of the element matches the pattern entered.
type — Overrides the type option for that custom group. 'unsorted' will not sort the group.
order — Overrides the order option for that custom group.
fallbackSort — Overrides the fallbackSort option for that custom group.
newlinesInside — Enforces a specific newline behavior between elements of the group.

Match importance

The customGroups list is ordered: The first custom group definition that matches an element will be used.

Custom groups have a higher priority than any predefined group.

Example

Put the WithId clause before anything else:

interface Interface extends WithId, Logged, StartupService {
 // ...
}

groups and customGroups configuration:

 {
   groups: [
     'withIdInterface',
     'unknown'
   ],
+  customGroups: [                    
+    {                                
+       groupName: 'withIdInterface'
+       elementNamePattern: '^WithId'
+    }                                
+  ]                                  
 }

Usage

// .eslintrc.js
module.exports = {
  plugins: [
    'perfectionist',
  ],
  rules: {
    'perfectionist/sort-heritage-clauses': [
      'error',
      {
        type: 'alphabetical',
        order: 'asc',
        fallbackSort: { type: 'unsorted' },
        ignoreCase: true,
        specialCharacters: 'keep',
        partitionByComment: false,
        partitionByNewLine: false,
        newlinesBetween: 'ignore',
        newlinesInside: 'ignore',
        groups: [],
        customGroups: [],
      },
    ],
  },
}

Version

This rule was introduced in v4.0.0.