8000 feat(eslint-plugin): [switch-exhaustiveness-check] add requireDefault… · c0sta/typescript-eslint@4cfcd45 · GitHub
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feat(eslint-plugin): [switch-exhaustiveness-check] add requireDefaultForNonUnion option (typescript-eslint#7880)
* rule(switch-exhaustiveness-check): add requireDefaultForNonUnion option * Apply suggestions from code review Co-authored-by: Josh Goldberg ✨ <git@joshuakgoldberg.com> * chore: apply suggestions to more locations * fix lint * Fix linting and ordering of md --------- Co-authored-by: Josh Goldberg ✨ <git@joshuakgoldberg.com>
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‎packages/eslint-plugin/docs/rules/switch-exhaustiveness-check.md

Lines changed: 24 additions & 1 deletion
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@@ -1,5 +1,5 @@
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---
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description: 'Require switch-case statements to be exhaustive with union types and enums.'
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description: 'Require switch-case statements to be exhaustive.'
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---
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> 🛑 This file is source code, not the primary documentation location! 🛑
@@ -11,6 +11,8 @@ However, if the union type or the enum changes, it's easy to forget to modify th
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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.
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There is also an option to check the exhaustiveness of switches on non-union types by requiring a default clause.
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## Examples
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When the switch doesn't have exhaustive cases, either filling them all out or adding a default will correct the rule's complaint.
@@ -179,6 +181,27 @@ switch (fruit) {
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<!--/tabs-->
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## Options
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### `requireDefaultForNonUnion`
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Examples of additional **incorrect** code for this rule with `{ requireDefaultForNonUnion: true }`:
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```ts option='{ "requireDefaultForNonUnion": true }' showPlaygroundButton
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const value: number = Math.floor(Math.random() * 3);
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switch (value) {
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case 0:
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return 0;
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case 1:
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return 1;
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}
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```
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Since `value` is a non-union type it requires the switch case to have a default clause only with `requireDefaultForNonUnion` enabled.
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<!--/tabs-->
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## When Not To Use It
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If you don't frequently `switch` over union types or enums with many parts, or intentionally wish to leave out some parts.

‎packages/eslint-plugin/src/rules/switch-exhaustiveness-check.ts

Lines changed: 57 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -12,25 +12,47 @@ import {
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requiresQuoting,
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} from '../util';
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export default createRule({
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type MessageIds = 'switchIsNotExhaustive' | 'addMissingCases';
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type Options = [
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{
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/**
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* If `true`, require a `default` clause for switches on non-union types.
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*
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* @default false
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*/
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requireDefaultForNonUnion?: boolean;
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},
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];
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export default createRule<Options, MessageIds>({
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name: 'switch-exhaustiveness-check',
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meta: {
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type: 'suggestion',
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docs: {
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description:
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'Require switch-case statements to be exhaustive with union types and enums',
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description: 'Require switch-case statements to be exhaustive',
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requiresTypeChecking: true,
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},
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hasSuggestions: true,
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schema: [],
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schema: [
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{
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type: 'object',
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additionalProperties: false,
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properties: {
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requireDefaultForNonUnion: {
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description: `If 'true', require a 'default' clause for switches on non-union types.`,
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type: 'boolean',
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},
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},
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},
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],
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messages: {
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switchIsNotExhaustive:
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'Switch is not exhaustive. Cases not matched: {{missingBranches}}',
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addMissingCases: 'Add branches for missing cases.',
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},
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},
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defaultOptions: [],
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create(context) {
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defaultOptions: [{ requireDefaultForNonUnion: false }],
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create(context, [{ requireDefaultForNonUnion }]) {
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const sourceCode = getSourceCode(context);
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const services = getParserServices(context);
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const checker = services.program.getTypeChecker();
@@ -39,9 +61,9 @@ export default createRule({
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function fixSwitch(
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fixer: TSESLint.RuleFixer,
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node: TSESTree.SwitchStatement,
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missingBranchTypes: ts.Type[],
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missingBranchTypes: (ts.Type | null)[], // null means default branch
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symbolName?: string,
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): TSESLint.RuleFix | null {
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): TSESLint.RuleFix {
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const lastCase =
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node.cases.length > 0 ? node.cases[node.cases.length - 1] : null;
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const caseIndent = lastCase
@@ -52,6 +74,10 @@ export default createRule({
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const missingCases = [];
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for (const missingBranchType of missingBranchTypes) {
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if (missingBranchType == null) {
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missingCases.push(`default: { throw new Error('default case') }`);
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continue;
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}
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// While running this rule on checker.ts of TypeScript project
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// the fix introduced a compiler error due to:
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//
@@ -159,7 +185,7 @@ export default createRule({
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suggest: [
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{
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messageId: 'addMissingCases',
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fix(fixer): TSESLint.RuleFix | null {
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fix(fixer): TSESLint.RuleFix {
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return fixSwitch(
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fixer,
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node,
@@ -170,6 +196,28 @@ export default createRule({
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},
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],
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});
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} else if (requireDefaultForNonUnion) {
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const hasDefault = node.cases.some(
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switchCase => switchCase.test == null,
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);
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if (!hasDefault) {
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context.report({
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node: node.discriminant,
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messageId: 'switchIsNotExhaustive',
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data: {
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missingBranches: 'default',
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},
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suggest: [
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{
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messageId: 'addMissingCases',
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fix(fixer): TSESLint.RuleFix {
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return fixSwitch(fixer, node, [null]);
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},
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},
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],
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});
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}
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}
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}
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‎packages/eslint-plugin/tests/rules/switch-exhaustiveness-check.test.ts

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@@ -209,6 +209,21 @@ function test(value: ObjectUnion): number {
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}
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}
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`,
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// switch with default clause on non-union type
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{
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code: `
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declare const value: number;
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switch (value) {
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case 0:
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return 0;
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case 1:
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return 1;
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default:
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return -1;
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}
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`,
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options: [{ requireDefaultForNonUnion: true }],
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},
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],
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invalid: [
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{
@@ -595,6 +610,38 @@ function test(arg: Enum): string {
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case Enum['9test']: { throw new Error('Not implemented yet: Enum[\\'9test\\'] case') }
596611
case Enum.test: { throw new Error('Not implemented yet: Enum.test case') }
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}
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}
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`,
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},
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],
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},
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],
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},
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{
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code: `
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const value: number = Math.floor(Math.random() * 3);
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switch (value) {
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case 0:
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return 0;
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case 1:
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return 1;
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}
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`,
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options: [{ requireDefaultForNonUnion: true }],
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errors: [
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{
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messageId: 'switchIsNotExhaustive',
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suggestions: [
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{
636+
messageId: 'addMissingCases',
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output: `
638+
const value: number = Math.floor(Math.random() * 3);
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switch (value) {
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case 0:
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return 0;
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case 1:
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return 1;
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default: { throw new Error('default case') }
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}
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`,
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},

‎packages/eslint-plugin/tests/schema-snapshots/switch-exhaustiveness-check.shot

Lines changed: 19 additions & 3 deletions
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