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feat(eslint-plugin): [no-duplicate-enum-values] add rule (#4833)
* feat(eslint-plugin): create a new rule to disallow duplicate enum values * fix(eslint-plugin): remove unused imported variable from no-duplicate-enum-values.test.ts * fix(eslint-plugin): test falsy values and fix some metadata * fix(eslint-plugin): make Enums in the falsy test valid Co-authored-by: Josh Goldberg <me@joshuakgoldberg.com>
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packages/eslint-plugin/docs/rules/no-duplicate-enum-values.md
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,51 @@ | ||
| # `no-duplicate-enum-values` | ||
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| Disallow duplicate enum member values. | ||
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| Although TypeScript supports duplicate enum member values, people usually expect members to have unique values within the same enum. Duplicate values can lead to bugs that are hard to track down. | ||
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| ## Rule Details | ||
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| This rule disallows defining an enum with multiple members initialized to the same value. Now it only enforces on enum members initialized with String or Number literals. Members without initializer or initialized with an expression are not checked by this rule. | ||
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| <!--tabs--> | ||
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| ### ❌ Incorrect | ||
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| ```ts | ||
| enum E { | ||
| A = 0, | ||
| B = 0, | ||
| } | ||
| ``` | ||
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| ```ts | ||
| enum E { | ||
| A = 'A' | ||
| B = 'A' | ||
| } | ||
| ``` | ||
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| ### ✅ Correct | ||
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| ```ts | ||
| enum E { | ||
| A = 0, | ||
| B = 1, | ||
| } | ||
| ``` | ||
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| ```ts | ||
| enum E { | ||
| A = 'A' | ||
| B = 'B' | ||
| } | ||
| ``` | ||
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| This rule is not configurable. | ||
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| ## Attributes | ||
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| - [ ] ✅ Recommended | ||
| - [ ] 🔧 Fixable | ||
| - [ ] 💭 Requires type information |
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72 changes: 72 additions & 0 deletions
72
packages/eslint-plugin/src/rules/no-duplicate-enum-values.ts
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| import { AST_NODE_TYPES, TSESTree } from '@typescript-eslint/utils'; | ||
| import * as util from '../util'; | ||
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| export default util.createRule({ | ||
| name: 'no-duplicate-enum-values', | ||
| meta: { | ||
| type: 'problem', | ||
| docs: { | ||
| description: 'Disallow duplicate enum member values', | ||
| recommended: false, | ||
| }, | ||
| hasSuggestions: true, | ||
| messages: { | ||
| duplicateValue: 'Duplicate enum member value {{value}}.', | ||
| }, | ||
| schema: [], | ||
| }, | ||
| defaultOptions: [], | ||
| create(context) { | ||
| function isStringLiteral( | ||
| node: TSESTree.Expression, | ||
| ): node is TSESTree.StringLiteral { | ||
| return ( | ||
| node.type === AST_NODE_TYPES.Literal && typeof node.value === 'string' | ||
| ); | ||
| } | ||
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| function isNumberLiteral( | ||
| node: TSESTree.Expression, | ||
| ): node is TSESTree.NumberLiteral { | ||
| return ( | ||
| node.type === AST_NODE_TYPES.Literal && typeof node.value === 'number' | ||
| ); | ||
| } | ||
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| return { | ||
| TSEnumDeclaration(node: TSESTree.TSEnumDeclaration): void { | ||
| const enumMembers = node.members; | ||
| const seenValues = new Set<number | string>(); | ||
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| enumMembers.forEach(member => { | ||
| if (member.initializer === undefined) { | ||
| return; | ||
| } | ||
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| let value: string | number | undefined; | ||
| if (isStringLiteral(member.initializer)) { | ||
| value = String(member.initializer.value); | ||
| } else if (isNumberLiteral(member.initializer)) { | ||
| value = Number(member.initializer.value); | ||
| } | ||
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| if (value === undefined) { | ||
| return; | ||
| } | ||
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| if (seenValues.has(value)) { | ||
| context.report({ | ||
| node: member, | ||
| messageId: 'duplicateValue', | ||
| data: { | ||
| value, | ||
| }, | ||
| }); | ||
| } else { | ||
| seenValues.add(value); | ||
| } | ||
| }); | ||
| }, | ||
| }; | ||
| }, | ||
| }); |
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packages/eslint-plugin/tests/rules/no-duplicate-enum-values.test.ts
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| import rule from '../../src/rules/no-duplicate-enum-values'; | ||
| import { RuleTester } from '../RuleTester'; | ||
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| const ruleTester = new RuleTester({ | ||
| parser: '@typescript-eslint/parser', | ||
| }); | ||
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| ruleTester.run('no-duplicate-enum-values', rule, { | ||
| valid: [ | ||
| ` | ||
| enum E { | ||
| A, | ||
| B, | ||
| } | ||
| `, | ||
| ` | ||
| enum E { | ||
| A = 1, | ||
| B, | ||
| } | ||
| `, | ||
| ` | ||
| enum E { | ||
| A = 1, | ||
| B = 2, | ||
| } | ||
| `, | ||
| ` | ||
| enum E { | ||
| A = 'A', | ||
| B = 'B', | ||
| } | ||
| `, | ||
| ` | ||
| enum E { | ||
| A = 'A', | ||
| B = 'B', | ||
| C, | ||
| } | ||
| `, | ||
| ` | ||
| enum E { | ||
| A = 'A', | ||
| B = 'B', | ||
| C = 2, | ||
| D = 1 + 1, | ||
| } | ||
| `, | ||
| ` | ||
| enum E { | ||
| A = 3, | ||
| B = 2, | ||
| C, | ||
| } | ||
| `, | ||
| ` | ||
| enum E { | ||
| A = 'A', | ||
| B = 'B', | ||
| C = 2, | ||
| D = foo(), | ||
| } | ||
| `, | ||
| ` | ||
| enum E { | ||
| A = '', | ||
| B = 0, | ||
| } | ||
| `, | ||
| ` | ||
| enum E { | ||
| A = 0, | ||
| B = -0, | ||
| C = NaN, | ||
| } | ||
| `, | ||
| ], | ||
| invalid: [ | ||
| { | ||
| code: ` | ||
| enum E { | ||
| A = 1, | ||
| B = 1, | ||
| } | ||
| `, | ||
| errors: [ | ||
| { | ||
| line: 4, | ||
| column: 3, | ||
| messageId: 'duplicateValue', | ||
| data: { value: 1 }, | ||
| }, | ||
| ], | ||
| }, | ||
| { | ||
| code: ` | ||
| enum E { | ||
| A = 'A', | ||
| B = 'A', | ||
| } | ||
| `, | ||
| errors: [ | ||
| { | ||
| line: 4, | ||
| column: 3, | ||
| messageId: 'duplicateValue', | ||
| data: { value: 'A' }, | ||
| }, | ||
| ], | ||
| }, | ||
| { | ||
| code: ` | ||
| enum E { | ||
| A = 'A', | ||
| B = 'A', | ||
| C = 1, | ||
| D = 1, | ||
| } | ||
| `, | ||
| errors: [ | ||
| { | ||
| line: 4, | ||
| column: 3, | ||
| messageId: 'duplicateValue', | ||
| data: { value: 'A' }, | ||
| }, | ||
| { | ||
| line: 6, | ||
| column: 3, | ||
| messageId: 'duplicateValue', | ||
| data: { value: 1 }, | ||
| }, | ||
| ], | ||
| }, | ||
| ], | ||
| }); |