noDuplicateFields (GraphQL)

Language GraphQL

Summary

Rule available since: v1.9.0
Diagnostic Category: lint/suspicious/noDuplicateFields
This rule is recommended, meaning it is enabled by default.
This rule doesn’t have a fix.
The default severity of this rule is information.
Sources:
- Same as @graphql-eslint/no-duplicate-fields

How to configure

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{
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  "linter": {
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    "rules": {
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      "suspicious": {
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        "noDuplicateFields": "error"
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      }
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    }
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  }
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}

Description

Disallow duplicate names inside GraphQL operations.

The rule checks selected fields within each selection set, variables declared by an operation, and arguments passed to a field. Each name must appear only once in its list.

Examples

Invalid

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query {
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  users {
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    id
4
    name
5
    email
6
    name
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  }
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}

code-block.graphql:4:5 lint/suspicious/noDuplicateFields ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ The field `name` is defined multiple times.
  
    2 │   users {
    3 │     id
  > 4 │     name
      │     ^^^^
    5 │     email
    6 │     name
  
  ℹ The field `name` is repeated here.
  
    4 │     name
    5 │     email
  > 6 │     name
      │     ^^^^
    7 │   }
    8 │ }
  
  ℹ Defining the same name more than once is not allowed, even when the duplicates could be merged.
  
  ℹ Remove the duplicated field.

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query {
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  users(
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    first: 100,
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    after: 10,
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    filter: "test",
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    first: 50
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  ) {
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    id
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  }
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}

code-block.graphql:3:5 lint/suspicious/noDuplicateFields ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ The argument `first` is defined multiple times.
  
    1 │ query {
    2 │   users(
  > 3 │     first: 100,
      │     ^^^^^
    4 │     after: 10,
    5 │     filter: "test",
  
  ℹ The argument `first` is repeated here.
  
    4 │     after: 10,
    5 │     filter: "test",
  > 6 │     first: 50
      │     ^^^^^
    7 │   ) {
    8 │     id
  
  ℹ Defining the same name more than once is not allowed, even when the duplicates could be merged.
  
  ℹ Remove the duplicated argument.

1
query ($v: String, $t: String, $v: String) {
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  id
3
}

code-block.graphql:1:9 lint/suspicious/noDuplicateFields ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ The variable `v` is defined multiple times.
  
  > 1 │ query ($v: String, $t: String, $v: String) {
      │         ^
    2 │   id
    3 │ }
  
  ℹ The variable `v` is repeated here.
  
  > 1 │ query ($v: String, $t: String, $v: String) {
      │                                 ^
    2 │   id
    3 │ }
  
  ℹ Defining the same name more than once is not allowed, even when the duplicates could be merged.
  
  ℹ Remove the duplicated variable.

Valid

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query {
2
  users {
3
    id
4
    name
5
    email
6
  }
7
}