1 | # `no-empty-interface`
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2 |
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3 | Disallow the declaration of empty interfaces.
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4 |
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5 | An empty interface is equivalent to its supertype. If the interface does not implement a supertype, then
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6 | the interface is equivalent to an empty object (`{}`). In both cases it can be omitted.
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7 |
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8 | ## Rule Details
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9 |
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10 | This rule aims to ensure that only meaningful interfaces are declared in the code.
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11 |
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12 |
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13 |
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14 | ### ❌ Incorrect
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15 |
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16 | ```ts
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17 | // an empty interface
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18 | interface Foo {}
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19 |
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20 | // an interface with only one supertype (Bar === Foo)
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21 | interface Bar extends Foo {}
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22 |
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23 | // an interface with an empty list of supertypes
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24 | interface Baz {}
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25 | ```
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26 |
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27 | ### ✅ Correct
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28 |
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29 | ```ts
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30 | // an interface with any number of members
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31 | interface Foo {
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32 | name: string;
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33 | }
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34 |
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35 | // same as above
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36 | interface Bar {
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37 | age: number;
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38 | }
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39 |
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40 | // an interface with more than one supertype
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41 | // in this case the interface can be used as a replacement of a union type.
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42 | interface Baz extends Foo, Bar {}
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43 | ```
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44 |
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45 |
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46 |
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47 | ### Options
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48 |
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49 | This rule accepts a single object option with the following default configuration:
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50 |
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51 | ```json
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52 | {
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53 | "@typescript-eslint/no-empty-interface": [
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54 | "error",
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55 | {
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56 | "allowSingleExtends": false
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57 | }
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58 | ]
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59 | }
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60 | ```
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61 |
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62 | - `allowSingleExtends: true` will silence warnings about extending a single interface without adding additional members
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63 |
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64 | ## When Not To Use It
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65 |
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66 | If you don't care about having empty/meaningless interfaces, then you will not need this rule.
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67 |
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68 | ## Related To
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69 |
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70 | - TSLint: [no-empty-interface](https://palantir.github.io/tslint/rules/no-empty-interface/)
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71 |
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72 | ## Attributes
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73 |
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74 | - Configs:
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75 | - [x] ✅ Recommended
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76 | - [x] 🔒 Strict
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77 | - [x] 🔧 Fixable
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78 | - [ ] 💭 Requires type information
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