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fix(eslint-plugin): [switch-exhaustiveness-check] enum members with new line or single quotes are not being fixed correctly #7806

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78 changes: 73 additions & 5 deletions packages/eslint-plugin/docs/rules/switch-exhaustiveness-check.md
Original file line number Diff line number Diff line change
@@ -1,15 +1,15 @@
---
description: 'Require switch-case statements to be exhaustive with union type.'
description: 'Require switch-case statements to be exhaustive with union type or enum.'
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[Proofreading] Existing typo with the singular/plural, heh:

Suggested change
description: 'Require switch-case statements to be exhaustive with union type or enum.'
description: 'Require switch-case statements to be exhaustive with union types and enums.'

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Done

---

> 🛑 This file is source code, not the primary documentation location! 🛑
>
> See **https://typescript-eslint.io/rules/switch-exhaustiveness-check** for documentation.

When working with union types in TypeScript, it's common to want to write a `switch` statement intended to contain a `case` for each constituent (possible type in the union).
However, if the union type changes, it's easy to forget to modify the cases to account for any new types.
When working with union types or enums in TypeScript, it's common to want to write a `switch` statement intended to contain a `case` for each constituent (possible type in the union or the enum).
However, if the union type or the enum 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 is missing a case for any of those literal types and does not have a `default` clause.
This rule reports when a `switch` statement over a value typed as a union of literals or as an enum is missing a case for any of those literal types and does not have a `default` clause.

## Examples

Expand Down Expand Up @@ -101,6 +101,74 @@ switch (day) {
}
```

<!--tabs-->

### ❌ Incorrect

Comment on lines +112 to +115
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@StyleShit StyleShit Oct 20, 2023

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it's probably not displayed correctly, would be happy to get some help here regarding how we should display this (maybe add a subtitle?):

https://deploy-preview-7806--typescript-eslint.netlify.app/rules/switch-exhaustiveness-check#examples

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<!-- /tabs --> is what you're looking for.

I'd also request a brief sentence before each of the examples explaining what they're for. It's kind of hard to piece together just from the code.

Vague starting proposal (just off the top of my head, not attached to this):

When the switch doesn't have exhaustive cases, either filling them all out or adding a default will correct the rule's complaint.

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yup

```ts
enum Fruit {
Apple,
Banana,
Cherry,
}

const fruit = Fruit.Cherry as Fruit;
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[Style] This is a little closer to the intent:

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const fruit = Fruit.Cherry as Fruit;
declare const fruit: Fruit;

(this and elsewhere)

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yup, I actually wanted to do that, but followed the existing code
changed :)


switch (fruit) {
case Fruit.Apple:
console.log('an apple');
break;
}
```

### ✅ Correct

```ts
enum Fruit {
Apple,
Banana,
Cherry,
}

const fruit = Fruit.Cherry as Fruit;

switch (fruit) {
case Fruit.Apple:
console.log('an apple');
break;

case Fruit.Banana:
console.log('a banana');
break;

case Fruit.Cherry:
console.log('a cherry');
break;
}
```

### ✅ Correct

```ts
enum Fruit {
Apple,
Banana,
Cherry,
}

const fruit = Fruit.Cherry as Fruit;

switch (fruit) {
case Fruit.Apple:
console.log('an apple');
break;

default:
console.log('a fruit');
break;
}
```

## When Not To Use It

If you don't frequently `switch` over union types with many parts, or intentionally wish to leave out some parts.
If you don't frequently `switch` over union types or enums with many parts, or intentionally wish to leave out some parts.
15 changes: 12 additions & 3 deletions packages/eslint-plugin/src/rules/switch-exhaustiveness-check.ts
Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ export default createRule({
type: 'suggestion',
docs: {
description:
'Require switch-case statements to be exhaustive with union type',
'Require switch-case statements to be exhaustive with union type or enum',
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(same existing typo-ish)

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'Require switch-case statements to be exhaustive with union type or enum',
'Require switch-case statements to be exhaustive with union types or enums',

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Done

requiresTypeChecking: true,
},
hasSuggestions: true,
Expand Down Expand Up @@ -66,17 +66,26 @@ export default createRule({
}

const missingBranchName = missingBranchType.getSymbol()?.escapedName;
const requiresBackticks = missingBranchName?.match(/[\r\n]/g);
let caseTest = checker.typeToString(missingBranchType);

if (
symbolName &&
(missingBranchName || missingBranchName === '') &&
requiresQuoting(missingBranchName.toString(), compilerOptions.target)
) {
caseTest = `${symbolName}['${missingBranchName}']`;
caseTest = requiresBackticks
? `${symbolName}[\`${missingBranchName}\`]`
: `${symbolName}['${missingBranchName}']`;
}

const errorMessage = `Not implemented yet: ${caseTest} case`;
// escape single quotes and newlines, so that the error message is a readable and valid code.
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Suggested change
// escape single quotes and newlines, so that the error message is a readable and valid code.
// escape single quotes and newlines, so that the error message is readable and valid code.

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I'm gonna learn English here more than ASTs

const escapedCaseTest = caseTest
.replace(/'/g, "\\'")
.replace(/\n/g, '\\n')
.replace(/\r/g, '\\r');

const errorMessage = `Not implemented yet: ${escapedCaseTest} case`;

missingCases.push(
`case ${caseTest}: { throw new Error('${errorMessage}') }`,
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -518,7 +518,7 @@ export enum Enum {

function test(arg: Enum): string {
switch (arg) {
case Enum['test-test']: { throw new Error('Not implemented yet: Enum['test-test'] case') }
case Enum['test-test']: { throw new Error('Not implemented yet: Enum[\\'test-test\\'] case') }
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case Enum.test: { throw new Error('Not implemented yet: Enum.test case') }
}
}
Expand Down Expand Up @@ -555,7 +555,7 @@ export enum Enum {

function test(arg: Enum): string {
switch (arg) {
case Enum['']: { throw new Error('Not implemented yet: Enum[''] case') }
case Enum['']: { throw new Error('Not implemented yet: Enum[\\'\\'] case') }
case Enum.test: { throw new Error('Not implemented yet: Enum.test case') }
}
}
Expand Down Expand Up @@ -592,7 +592,7 @@ export enum Enum {

function test(arg: Enum): string {
switch (arg) {
case Enum['9test']: { throw new Error('Not implemented yet: Enum['9test'] case') }
case Enum['9test']: { throw new Error('Not implemented yet: Enum[\\'9test\\'] case') }
case Enum.test: { throw new Error('Not implemented yet: Enum.test case') }
}
}
Expand All @@ -602,5 +602,47 @@ function test(arg: Enum): string {
},
],
},
{
code: `
enum Enum {
'a' = 1,
[\`key-with

new-line\`] = 2,
}

declare const a: Enum;

switch (a) {
}
`,
errors: [
{
messageId: 'switchIsNotExhaustive',
suggestions: [
{
messageId: 'addMissingCases',
output: `
enum Enum {
'a' = 1,
[\`key-with

new-line\`] = 2,
}

declare const a: Enum;

switch (a) {
case Enum.a: { throw new Error('Not implemented yet: Enum.a case') }
case Enum[\`key-with

new-line\`]: { throw new Error('Not implemented yet: Enum[\`key-with\\n\\n new-line\`] case') }
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wasn't sure about this. should we throw an error with actual new lines or \n is fine?

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Yeah good question. It's such a rare case, I don't think it matters too much. But in general having error messages be on one line is easier to read.

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should we just strip out any spaces, tabs, and new lines?

OK... it might look weird in some cases... IDK

key = `key-with
          new-line`

error = "not implemented: 'key-withnew-line'";

anyway, as you said, it's a rare case that probably isn't worth the effort

}
`,
},
],
},
],
},
],
});