eslint-plugin-rxjs

What is eslint-plugin-rxjs?

eslint-plugin-rxjs is an ESLint plugin that provides linting rules for RxJS to help developers write more consistent and error-free reactive code. It enforces best practices and helps catch common mistakes when working with RxJS.

What are eslint-plugin-rxjs's main functionalities?

Enforce Creation Operators

This rule disallows the creation of new Observables using the constructor. Instead, it encourages the use of creation operators like `of`, `from`, etc.

/* eslint rxjs/no-create: 'error' */
import { Observable } from 'rxjs';
const observable = new Observable(observer => {
  observer.next('Hello World');
  observer.complete();
});

No Ignored Subscription

This rule ensures that subscriptions are not ignored. It helps in avoiding memory leaks by making sure that all subscriptions are properly handled.

/* eslint rxjs/no-ignored-subscription: 'error' */
import { of } from 'rxjs';
of('Hello World').subscribe();

No Subject Unsubscribe

This rule disallows calling `unsubscribe` on Subjects, as it can lead to unexpected behavior. Instead, it encourages the use of `complete`.

/* eslint rxjs/no-subject-unsubscribe: 'error' */
import { Subject } from 'rxjs';
const subject = new Subject();
subject.unsubscribe();

Other packages similar to eslint-plugin-rxjs

eslint-plugin-rxjs-angular

eslint-plugin-rxjs-angular is an ESLint plugin specifically designed for Angular projects using RxJS. It provides additional rules that are tailored for Angular's use of RxJS, such as enforcing the use of Angular's `async` pipe and ensuring proper use of Angular's `HttpClient`.

README

eslint-plugin-rxjs

This package contains a bunch of ESLint rules for RxJS. Essentially, it's a re-implementation of the rules that are in the rxjs-tslint-rules package. (The Angular-specific rules in rxjs-tslint-rules have been re-implemented in eslint-plugin-rxjs-angular.)

Some of the rules are rather opinionated and are not included in the recommended configuration. Developers can decide for themselves whether they want to enable opinionated rules.

Almost all of these rules require the TypeScript parser for ESLint.

Install

Install the ESLint TypeScript parser using npm:

npm install @typescript-eslint/parser --save-dev

Install the package using npm:

npm install eslint-plugin-rxjs --save-dev

Configure the parser and the parserOptions for ESLint. Here, I use a .eslintrc.js file for the configuration:

const { join } = require("path");
module.exports = {
  parser: "@typescript-eslint/parser",
  parserOptions: {
    ecmaVersion: 2019,
    project: join(__dirname, "./tsconfig.json"),
    sourceType: "module"
  },
  plugins: ["rxjs"],
  extends: [],
  rules: {
    "rxjs/no-async-subscribe": "error",
    "rxjs/no-ignored-observable": "error",
    "rxjs/no-ignored-subscription": "error",
    "rxjs/no-nested-subscribe": "error",
    "rxjs/no-unbound-methods": "error",
    "rxjs/throw-error": "error"
  }
};

Or, using the recommended configuration:

const { join } = require("path");
module.exports = {
  parser: "@typescript-eslint/parser",
  parserOptions: {
    ecmaVersion: 2019,
    project: join(__dirname, "./tsconfig.json"),
    sourceType: "module"
  },
  extends: ["plugin:rxjs/recommended"],
};

Rules

The package includes the following rules.

Rules marked with ✅ are recommended and rules marked with 🔧 have fixers.

Rule	Description
ban-observables	Forbids the use of banned observables.
ban-operators	Forbids the use of banned operators.
finnish	Enforces the use of Finnish notation.
just	Enforces the use of a just alias for of.		🔧
no-async-subscribe	Forbids passing async functions to subscribe.	✅
no-compat	Forbids importation from locations that depend upon rxjs-compat.
no-connectable	Forbids operators that return connectable observables.
no-create	Forbids the calling of Observable.create.	✅
no-cyclic-action	Forbids effects and epics that re-emit filtered actions.
no-explicit-generics	Forbids explicit generic type arguments.
no-exposed-subjects	Forbids exposed (i.e. non-private) subjects.
no-finnish	Forbids the use of Finnish notation.
no-ignored-error	Forbids the calling of subscribe without specifying an error handler.
no-ignored-notifier	Forbids observables not composed from the repeatWhen or retryWhen notifier.	✅
no-ignored-observable	Forbids the ignoring of observables returned by functions.
no-ignored-replay-buffer	Forbids using ReplaySubject, publishReplay or shareReplay without specifying the buffer size.	✅
no-ignored-subscribe	Forbids the calling of subscribe without specifying arguments.
no-ignored-subscription	Forbids ignoring the subscription returned by subscribe.
no-ignored-takewhile-value	Forbids ignoring the value within takeWhile.	✅
no-implicit-any-catch	Like the no-implicit-any-catch rule in @typescript-eslint/eslint-plugin, but for the catchError operator instead of catch clauses.	✅	🔧
no-index	Forbids the importation from index modules - for the reason, see this issue.	✅
no-internal	Forbids the importation of internals.	✅	🔧
no-nested-subscribe	Forbids the calling of subscribe within a subscribe callback.	✅
no-redundant-notify	Forbids redundant notifications from completed or errored observables.	✅
no-sharereplay	Forbids using the shareReplay operator.	✅
no-subclass	Forbids subclassing RxJS classes.
no-subject-unsubscribe	Forbids calling the unsubscribe method of a subject instance.	✅
no-subject-value	Forbids accessing the value property of a BehaviorSubject instance.
no-subscribe-handlers	Forbids the passing of handlers to subscribe.
no-topromise	Forbids the use of the toPromise method.
no-unbound-methods	Forbids the passing of unbound methods.	✅
no-unsafe-catch	Forbids unsafe catchError usage in effects and epics.
no-unsafe-first	Forbids unsafe first/take usage in effects and epics.
no-unsafe-subject-next	Forbids unsafe optional next calls.	✅
no-unsafe-switchmap	Forbids unsafe switchMap usage in effects and epics.
no-unsafe-takeuntil	Forbids the application of operators after takeUntil.	✅
prefer-observer	Forbids the passing separate handlers to subscribe and tap.		🔧
suffix-subjects	Enforces the use of a suffix in subject identifiers.
throw-error	Enforces the passing of Error values to error notifications.