noUselessFallbackInSpread (JavaScript)

Language JavaScript (and super languages)

Summary

Diagnostic Category: lint/nursery/noUselessFallbackInSpread
This rule has an unsafe fix.
The default severity of this rule is warning.
Sources:
- Same as unicorn/no-useless-fallback-in-spread

How to configure

1
{
2
  "linter": {
3
    "rules": {
4
      "nursery": {
5
        "noUselessFallbackInSpread": "error"
6
      }
7
    }
8
  }
9
}

Description

Disallow empty object fallbacks when spreading a value into an object.

Spreading null, undefined, or another falsy value (a value treated as false in a condition, such as false, 0, or "") into an object literal adds no properties. Writing {...(value || {})} or {...(value ?? {})} therefore gives the same result as {...value}, and the {} fallback only adds noise.

This doesn’t apply to arrays: spreading null or undefined into an array or a function call throws an error, so [...(value || [])] is allowed.

Examples

Invalid

1
const object = { ...(options || {}) };

code-block.js:1:30 lint/nursery/noUselessFallbackInSpread  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ This empty object fallback is unnecessary.
  
  > 1 │ const object = { ...(options || {}) };
      │                              ^^^^^
    2 │ 
  
  ℹ Spreading null, undefined, or another falsy value such as false, 0, or "" into an object adds no properties, so the fallback has no effect.
  
  ℹ Remove the fallback and spread the value directly.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.
  
  ℹ Unsafe fix: Remove the empty object fallback.
  
    1 │ const·object·=·{·...(options·||·{})·};
      │                     -       -------

1
const object = { ...(options ?? {}) };

code-block.js:1:30 lint/nursery/noUselessFallbackInSpread  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ This empty object fallback is unnecessary.
  
  > 1 │ const object = { ...(options ?? {}) };
      │                              ^^^^^
    2 │ 
  
  ℹ Spreading null, undefined, or another falsy value such as false, 0, or "" into an object adds no properties, so the fallback has no effect.
  
  ℹ Remove the fallback and spread the value directly.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.
  
  ℹ Unsafe fix: Remove the empty object fallback.
  
    1 │ const·object·=·{·...(options·??·{})·};
      │                     -       -------

Valid

1
const object = { ...options };
2
const withDefaults = { ...(options || { verbose: true }) };
3
const conditional = { ...(enabled && {}) };
4
const array = [...(items || [])];