sort-constructor-parameters

Enforce sorted constructor parameters on classes matching configured conditions.

This rule does not sort constructor parameters by default. It must be configured with useConfigurationIf to target only the classes where parameter order does not matter (e.g., classes using dependency injection).

By keeping those constructor parameters sorted, developers can quickly scan and verify the dependencies, making the code more predictable and reducing the likelihood of errors.

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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 and newlines behavior are 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'
| 'subgroup-order'
| 'unsorted'
order?: 'asc' | 'desc'
}}_{default: { type: 'unsorted' }}

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

You can also sort by subgroup order (nested groups in the groups option) using subgroup-order.

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 the constructor parameters into logical groups. This can help in organizing and maintaining constructors with many parameters by creating partitions based on comments.

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 constructor parameters if there is an empty line between them. This helps maintain the defined order of logically separated groups of parameters.

constructor(
  // Group 1
  private authService: AuthService,
  private userService: UserService,

  // Group 2
  private logger: LoggerService,
  private router: Router,
) {}

Each group of parameters (separated by empty lines) is treated independently, and the order within each group is preserved.

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.

useConfigurationIf

Important

This option must be explicitly set in each configuration object.

_{type:
{
allNamesMatchPattern?:
| string
| string[]
| { pattern: string; flags: string }
| { pattern: string; flags: string }[]
matchesAstSelector?: string
}}

Specifies filters to match a particular options configuration for a given constructor.

The first matching options configuration will be used. If no configuration matches, the constructor is left unsorted. No fallback configuration is applied.

allNamesMatchPattern — A regexp pattern that all constructor parameter names must match.
matchesAstSelector — An AST selector matching a MethodDefinition node. To avoid unexpected behavior, do not use :exit or :enter pseudo-selectors.

Example configuration: only sort constructors of Angular components, services, and pipes.

{
  'perfectionist/sort-constructor-parameters': [
    'error',
    {
      useConfigurationIf: {
        matchesAstSelector: 'ClassDeclaration:has(Decorator[expression.callee.name=/^(Component|Injectable|Pipe)$/]) > ClassBody > MethodDefinition',
      },
      type: 'alphabetical',
    },
  ],
}

groups

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

Specifies a list of groups for sorting. Groups help organize elements into categories.

Each element 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.

Predefined groups are characterized by a selector.

Selectors

'parameter' — Constructor parameters that are not rest elements.

Note: Rest elements (...args) are not sorted and act as partition boundaries. This ensures the original order of rest elements is preserved.

Modifiers

Modifiers are listed below by importance, from most to least important:

'decorated' — Matches parameters with at least one decorator.
'override' — Matches parameters declared with the override keyword.
'readonly' — Matches parameters declared with the readonly keyword.
'protected' — Matches parameters declared with the protected keyword.
'private' — Matches parameters declared with the private keyword.
'public' — Matches parameters declared with the public keyword, or without visibility keyword.

Example: decorated-readonly-public-parameter.

Important notes

Scope of the `public` modifier

Parameters that are neither protected nor private are matched with the public modifier, even if the keyword is absent. This includes plain parameters that are not parameter properties.

The `unknown` group

Parameters that don’t fit into any group specified in the groups option will be placed in the unknown group. If the unknown group is not specified in the groups option, the parameters will remain in their original order.

Behavior when multiple groups match a parameter

The list of modifiers above is sorted by importance, from most to least important. When several groups match a parameter, the following rules apply:

The group with the most matching modifiers is selected.
If the number of matching modifiers is the same, the group is chosen based on modifier importance as listed above.

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 — Overrides the newlinesInside option for that group.

{
  groups: [
    'parameter',
  ]
}

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

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

Defines custom groups to match specific constructor parameters.

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'
  selector?: string
  modifiers?: string[]
  elementNamePattern?: string | string[] | { pattern: string; flags?: string } | { pattern: string; flags?: string }[]
  decoratorNamePattern?: string | string[] | { pattern: string; flags?: string } | { pattern: string; flags?: string }[]
}

A constructor parameter 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
      modifiers?: string[]
      elementNamePattern?: string | string[] | { pattern: string; flags?: string } | { pattern: string; flags?: string }[]
      decoratorNamePattern?: string | string[] | { pattern: string; flags?: string } | { pattern: string; flags?: string }[]
  }>
}

A constructor parameter will match a CustomGroupAnyOfDefinition group if it matches at least one of the anyOf items.

Attributes

groupName — The group’s name, which needs to be put in the groups option.
selector — Filter on the selector of the element.
modifiers — Filter on the modifiers of the element. (All the modifiers of the element must be present in that list)
elementNamePattern — If entered, will check that the name of the element matches the pattern entered.
decoratorNamePattern — If entered, will check that at least one decorator matches the pattern entered.
type — Overrides the type option for that custom group.
order — Overrides the order option for that custom group.
fallbackSort — Overrides the fallbackSort option for that custom group.
newlinesInside — Overrides the newlinesInside option for that custom group.

Match importance

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

sort-constructor-parameters

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Options

type

order

fallbackSort

alphabet

ignoreCase

specialCharacters

locales

partitionByComment

partitionByNewLine

newlinesBetween

newlinesInside

useConfigurationIf

groups

Selectors

Modifiers

Important notes

Scope of the `public` modifier

The `unknown` group

Behavior when multiple groups match a parameter

Group with overridden settings

Newlines between groups

customGroups

Attributes

Match importance

Usage

Version

Resources

Table of Contents

sort-constructor-parameters

Try it out

Options

type

order

fallbackSort

alphabet

ignoreCase

specialCharacters

locales

partitionByComment

partitionByNewLine

newlinesBetween

newlinesInside

useConfigurationIf

groups

Selectors

Modifiers

Important notes

Scope of the public modifier

The unknown group

Behavior when multiple groups match a parameter

Group with overridden settings

Newlines between groups

customGroups

Attributes

Match importance

Usage

Version

Resources

Table of Contents

Scope of the `public` modifier

The `unknown` group