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128 lines
2 KiB
Text
128 lines
2 KiB
Text
---
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description: 'Require switch-case statements to be exhaustive with union type.'
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---
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> 🛑 This file is source code, not the primary documentation location! 🛑
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>
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> See **https://typescript-eslint.io/rules/switch-exhaustiveness-check** for documentation.
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Union type may have a lot of parts. It's easy to forget to consider all cases in switch. This rule reminds which parts are missing. If domain of the problem requires to have only a partial switch, developer may _explicitly_ add a default clause.
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## Rule Details
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Examples of code for this rule:
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<!--tabs-->
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### ❌ Incorrect
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```ts
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type Day =
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| 'Monday'
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| 'Tuesday'
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| 'Wednesday'
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| 'Thursday'
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| 'Friday'
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| 'Saturday'
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| 'Sunday';
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const day = 'Monday' as Day;
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let result = 0;
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switch (day) {
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case 'Monday': {
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result = 1;
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break;
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}
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}
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```
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### ✅ Correct
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```ts
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type Day =
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| 'Monday'
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| 'Tuesday'
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| 'Wednesday'
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| 'Thursday'
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| 'Friday'
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| 'Saturday'
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| 'Sunday';
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const day = 'Monday' as Day;
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let result = 0;
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switch (day) {
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case 'Monday': {
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result = 1;
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break;
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}
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case 'Tuesday': {
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result = 2;
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break;
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}
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case 'Wednesday': {
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result = 3;
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break;
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}
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case 'Thursday': {
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result = 4;
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break;
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}
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case 'Friday': {
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result = 5;
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break;
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}
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case 'Saturday': {
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result = 6;
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break;
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}
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case 'Sunday': {
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result = 7;
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break;
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}
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}
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```
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### ✅ Correct
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```ts
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type Day =
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| 'Monday'
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| 'Tuesday'
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| 'Wednesday'
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| 'Thursday'
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| 'Friday'
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| 'Saturday'
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| 'Sunday';
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const day = 'Monday' as Day;
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let result = 0;
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switch (day) {
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case 'Monday': {
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result = 1;
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break;
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}
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default: {
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result = 42;
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}
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}
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```
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## Options
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```jsonc
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// .eslintrc.json
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{
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"rules": {
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"@typescript-eslint/switch-exhaustiveness-check": "warn"
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}
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}
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```
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This rule is not configurable.
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## When Not To Use It
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If program doesn't have union types with many parts. Downside of this rule is the need for type information, so it's slower than regular rules.
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