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fix(eslint-plugin): [switch-exhaustiveness-check] invert considerDefaultExhaustiveForUnions #10223

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Merged
merged 3 commits into from
Oct 29, 2024
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fix(eslint-plugin): [switch-exhaustiveness-check] invert considerDefaultExhaustiveForUnions #10223

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267d90a
flip boolean
kirkwaiblinger Oct 28, 2024
c57e32c
fix docs
kirkwaiblinger Oct 28, 2024
47b95f6
lint
kirkwaiblinger Oct 29, 2024
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42 changes: 8 additions & 34 deletions packages/eslint-plugin/docs/rules/switch-exhaustiveness-check.mdx
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Original file line number Diff line number Diff line change
Expand Up @@ -65,10 +65,7 @@ If set to true, a `switch` statement over a union type that includes a `default`
Otherwise, the rule enforces explicitly handling every constituent of the union type with their own explicit `case`.
Keeping this option disabled can be useful if you want to make sure every value added to the union receives explicit handling, with the `default` case reserved for reporting an error.

Examples of code with `{ considerDefaultExhaustiveForUnions: true }`:

<Tabs>
<TabItem value="❌ Incorrect">
Examples of additional **correct** code with `{ considerDefaultExhaustiveForUnions: true }`:

```ts option='{ "considerDefaultExhaustiveForUnions": true }' showPlaygroundButton
declare const literal: 'a' | 'b';
Expand All @@ -81,36 +78,9 @@ switch (literal) {
}
```

</TabItem>

<TabItem value="✅ Correct">

```ts option='{ "considerDefaultExhaustiveForUnions": true }' showPlaygroundButton
declare const literal: 'a' | 'b';

switch (literal) {
case 'a':
break;
case 'b':
break;
default:
break;
}

switch (literal) {
case 'a':
break;
case 'b':
break;
}
```

</TabItem>
</Tabs>

## Examples

When the switch doesn't have exhaustive cases, either filling them all out or adding a default will correct the rule's complaint.
When the switch doesn't have exhaustive cases, either filling them all out or adding a default (if you have `considerDefaultExhaustiveForUnions` enabled) will address the rule's complaint.

Here are some examples of code working with a union of literals:

Expand Down Expand Up @@ -181,7 +151,9 @@ switch (day) {
</TabItem>
<TabItem value="✅ Correct (Defaulted)">

```ts
```ts option='{ "considerDefaultExhaustiveForUnions": true }'
// requires `considerDefaultExhaustiveForUnions` to be set to true

type Day =
| 'Monday'
| 'Tuesday'
Expand Down Expand Up @@ -257,7 +229,9 @@ switch (fruit) {
</TabItem>
<TabItem value="✅ Correct (Defaulted)">

```ts
```ts option='{ "considerDefaultExhaustiveForUnions": true }'
// requires `considerDefaultExhaustiveForUnions` to be set to true

enum Fruit {
Apple,
Banana,
Expand Down
4 changes: 2 additions & 2 deletions packages/eslint-plugin/src/rules/switch-exhaustiveness-check.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -174,9 +174,9 @@ export default createRule<Options, MessageIds>({
const { defaultCase, missingLiteralBranchTypes, symbolName } =
switchMetadata;

// Unless considerDefaultExhaustiveForUnions is enabled, the presence of a default case
// If considerDefaultExhaustiveForUnions is enabled, the presence of a default case
// always makes the switch exhaustive.
if (!considerDefaultExhaustiveForUnions && defaultCase != null) {
if (considerDefaultExhaustiveForUnions && defaultCase != null) {
return;
}

Expand Down
44 changes: 12 additions & 32 deletions packages/eslint-plugin/tests/docs-eslint-output-snapshots/switch-exhaustiveness-check.shot
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37 changes: 18 additions & 19 deletions packages/eslint-plugin/tests/rules/switch-exhaustiveness-check.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -144,7 +144,8 @@ function test(value: Union): number {
}
`,
// Switch contains default clause.
`
{
code: `
type Day =
| 'Monday'
| 'Tuesday'
Expand All @@ -166,7 +167,13 @@ switch (day) {
result = 42;
}
}
`,
`,
options: [
{
considerDefaultExhaustiveForUnions: true,
},
],
},
// Exhaustiveness check only works for union types...
`
const day = 'Monday' as string;
Expand Down Expand Up @@ -553,6 +560,7 @@ switch (value) {
options: [
{
allowDefaultCaseForExhaustiveSwitch: true,
considerDefaultExhaustiveForUnions: true,
requireDefaultForNonUnion: false,
},
],
Expand All @@ -570,6 +578,7 @@ switch (value) {
options: [
{
allowDefaultCaseForExhaustiveSwitch: false,
considerDefaultExhaustiveForUnions: true,
requireDefaultForNonUnion: false,
},
],
Expand Down Expand Up @@ -745,6 +754,7 @@ switch (value) {
options: [
{
allowDefaultCaseForExhaustiveSwitch: true,
considerDefaultExhaustiveForUnions: true,
requireDefaultForNonUnion: true,
},
],
Expand All @@ -762,6 +772,7 @@ switch (value) {
options: [
{
allowDefaultCaseForExhaustiveSwitch: false,
considerDefaultExhaustiveForUnions: true,
requireDefaultForNonUnion: true,
},
],
Expand Down Expand Up @@ -832,8 +843,6 @@ declare const literal: 'a' | 'b';
switch (literal) {
case 'a':
break;
case 'b':
break;
default:
break;
}
Expand All @@ -857,7 +866,6 @@ switch (literal) {
options: [
{
allowDefaultCaseForExhaustiveSwitch: false,
considerDefaultExhaustiveForUnions: true,
},
],
},
Expand All @@ -876,8 +884,6 @@ switch (myEnum) {
break;
case MyEnum.Bar:
break;
case MyEnum.Baz:
break;
default: {
break;
}
Expand All @@ -895,8 +901,6 @@ declare const value: boolean;
switch (value) {
case false:
break;
case true:
break;
default: {
break;
}
Expand Down Expand Up @@ -2507,7 +2511,7 @@ switch (literal) {
],
options: [
{
considerDefaultExhaustiveForUnions: true,
considerDefaultExhaustiveForUnions: false,
},
],
},
Expand Down Expand Up @@ -2541,11 +2545,6 @@ switch (literal) {
],
},
],
options: [
{
considerDefaultExhaustiveForUnions: true,
},
],
},
{
code: `
Expand Down Expand Up @@ -2581,7 +2580,7 @@ switch (literal) {
],
options: [
{
considerDefaultExhaustiveForUnions: true,
considerDefaultExhaustiveForUnions: false,
},
],
},
Expand Down Expand Up @@ -2622,7 +2621,7 @@ switch (literal) {
],
options: [
{
considerDefaultExhaustiveForUnions: true,
considerDefaultExhaustiveForUnions: false,
},
],
},
Expand Down Expand Up @@ -2677,7 +2676,7 @@ switch (myEnum) {
],
options: [
{
considerDefaultExhaustiveForUnions: true,
considerDefaultExhaustiveForUnions: false,
},
],
},
Expand Down Expand Up @@ -2714,7 +2713,7 @@ switch (value) {
],
options: [
{
considerDefaultExhaustiveForUnions: true,
considerDefaultExhaustiveForUnions: false,
},
],
},
Expand Down
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