no-unsafe-subject-next.md

Disallow unsafe optional next calls (rxjs-x/no-unsafe-subject-next)

💼 This rule is enabled in the following configs: ✅ recommended, 🔒 strict.

💭 This rule requires type information.

This rule effects failures if next is called without an argument and the subject's value type is not void.

In RxJS version 6, the next method's value parameter was optional, but a value should always be specified for subjects with non-void element types. RxJS version 7 changed the value parameter to mandatory.

Rule details

Examples of incorrect code for this rule:

const subject = new Subject<number>();
subject.next();

Examples of correct code for this rule:

const subject = new Subject<void>();
subject.next();

const subject = new Subject<number>();
subject.next(0);

When Not To Use It

If you don't care about sending undefined to subjects, then you don't need this rule. Alternatively, you may rely on TypeScript to enforce the value parameter, which was made mandatory in RxJS version 7.

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

Resources

• Rule source
• Test source