useExhaustiveSwitchCases

JavaScript (and super languages)

Summary

Diagnostic Category: lint/nursery/useExhaustiveSwitchCases
This rule has an unsafe fix.
The default severity of this rule is information.
This rule belongs to the following domains:
- project
Sources:
- Same as @typescript-eslint/switch-exhaustiveness-check

Description

Require switch-case statements to be exhaustive.

When working with union types in TypeScript, it’s common to want to write a switch statement intended to contain a case for each possible variant. However, if the union type changes, it’s easy to forget to modify the cases to account for any new types.

This rule reports when a switch statement over a value typed as a union of literals lacks a case for any of those literal types and does not have a default clause.

Examples

Invalid

1
type Day =
2
  | 'Monday'
3
  | 'Tuesday'
4
  | 'Wednesday'
5
  | 'Thursday'
6
  | 'Friday'
7
  | 'Saturday'
8
  | 'Sunday';
9

10
declare const day: Day;
11
let result = 0;
12

13
switch (day) {
14
  case 'Monday':
15
    result = 1;
16
    break;
17
}

Valid

1
type Day =
2
  | 'Monday'
3
  | 'Tuesday'
4
  | 'Wednesday'
5
  | 'Thursday'
6
  | 'Friday'
7
  | 'Saturday'
8
  | 'Sunday';
9

10
declare const day: Day;
11
let result = 0;
12

13
switch (day) {
14
  case 'Monday':
15
    result = 1;
16
    break;
17
  case 'Tuesday':
18
    result = 2;
19
    break;
20
  case 'Wednesday':
21
    result = 3;
22
    break;
23
  case 'Thursday':
24
    result = 4;
25
    break;
26
  case 'Friday':
27
    result = 5;
28
    break;
29
  case 'Saturday':
30
    result = 6;
31
    break;
32
  case 'Sunday':
33
    result = 7;
34
    break;
35
}

How to configure

1
{
2
  "linter": {
3
    "rules": {
4
      "nursery": {
5
        "useExhaustiveSwitchCases": "error"
6
      }
7
    }
8
  }
9
}