Enforce the use of a suffix in subject identifiers (rxjs-x/suffix-subjects)

February 16, 2026 · View on GitHub

💭 This rule requires type information.

This rule effects failures if subject variables, properties and parameters don't conform to a naming scheme that identifies them as subjects.

Note

This rule is designed to be optionally compatible with finnish. Using Finnish notation (adding a $ suffix) your subject names will not cause a failure of this rule.

Rule details

Examples of incorrect code for this rule:

const answers = new Subject<number>();

Examples of correct code for this rule:

const answersSubject = new Subject<number>();
const answersSubject$ = new Subject<number>();

// The static observable creators that accept a sources object are exempt from this rule.
combineLatest({ answers: new Subject<number>() });

Options

NameDescriptionTypeDefault
objectsRequire for object literal keys.Booleantrue
parametersRequire for parameters.Booleantrue
propertiesRequire for properties, except object literal keys (see "objects" option).Booleantrue
suffixThe suffix to enforce.StringSubject
typesEnforce for specific types. Keys are a RegExp, values are a boolean.Object[object Object]
variablesRequire for variables.Booleantrue

This rule accepts a single option which is an object with properties that determine whether subject suffixes are enforced for parameters, properties, objects, and variables. It also contains a types property that determine whether or not the naming convention is to be enforced for specific types and a suffix property.

The default (Angular-friendly) configuration looks like this:

{
  "rxjs-x/suffix-subjects": [
    "error",
    {
      "parameters": true,
      "properties": true,
      "objects": true,
      "suffix": "Subject",
      "types": {
        "^EventEmitter$": false
      },
      "variables": true,
    }
  ]
}

The properties in the options object are themselves optional; they do not all have to be specified.

Tip

This rule will skip method enforcement if the override keyword is present. Users are encouraged to enable noImplicitOverride in their tsconfig.json to take advantage of this.

When Not To Use It

If you don't use suffixes on your project's subjects, then you don't need this rule. However, keep in mind that inconsistent style can harm readability in a project.

Type checked lint rules are more powerful than traditional lint rules, but also require configuring type checked linting.

Resources