noSelfAssign

Diagnostic Category: lint/correctness/noSelfAssign

JavaScript (and super languages)

Since: v1.0.0

Sources:

Same as: no-self-assign
Same as: self_assignment

Description

Disallow assignments where both sides are exactly the same.

Self assignments have no effect, so probably those are an error due to incomplete refactoring.

Examples

Invalid

a = a;

code-block.js:1:5 lint/correctness/noSelfAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ a is assigned to itself.
  
  > 1 │ a = a;
      │     ^
    2 │ 
  
  ℹ This is where is assigned.
  
  > 1 │ a = a;
      │ ^
    2 │

[a] = [a];

code-block.js:1:8 lint/correctness/noSelfAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ a is assigned to itself.
  
  > 1 │ [a] = [a];
      │        ^
    2 │ 
  
  ℹ This is where is assigned.
  
  > 1 │ [a] = [a];
      │  ^
    2 │

({a: b} = {a: b});

code-block.js:1:15 lint/correctness/noSelfAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ b is assigned to itself.
  
  > 1 │ ({a: b} = {a: b});
      │               ^
    2 │ 
  
  ℹ This is where is assigned.
  
  > 1 │ ({a: b} = {a: b});
      │      ^
    2 │

a.b = a.b;

code-block.js:1:9 lint/correctness/noSelfAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ b is assigned to itself.
  
  > 1 │ a.b = a.b;
      │         ^
    2 │ 
  
  ℹ This is where is assigned.
  
  > 1 │ a.b = a.b;
      │   ^
    2 │

a[b] = a[b];

code-block.js:1:10 lint/correctness/noSelfAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ b is assigned to itself.
  
  > 1 │ a[b] = a[b];
      │          ^
    2 │ 
  
  ℹ This is where is assigned.
  
  > 1 │ a[b] = a[b];
      │   ^
    2 │

a[b].foo = a[b].foo;

code-block.js:1:17 lint/correctness/noSelfAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ foo is assigned to itself.
  
  > 1 │ a[b].foo = a[b].foo;
      │                 ^^^
    2 │ 
  
  ℹ This is where is assigned.
  
  > 1 │ a[b].foo = a[b].foo;
      │      ^^^
    2 │

a['b'].foo = a['b'].foo;

code-block.js:1:21 lint/correctness/noSelfAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ foo is assigned to itself.
  
  > 1 │ a[‘b’].foo = a[‘b’].foo;
      │                     ^^^
    2 │ 
  
  ℹ This is where is assigned.
  
  > 1 │ a[‘b’].foo = a[‘b’].foo;
      │        ^^^
    2 │

Valid

a &= a;
var a = a;
let a = a;
const a = a;
[a, b] = [b, a];

How to configure

{
  "linter": {
    "rules": {
      "correctness": {
        "noSelfAssign": "error"
      }
    }
  }
}