noMissingThrow (JavaScript)

Language JavaScript (and super languages)

Summary

Rule available since: v2.6.5
Diagnostic Category: lint/nursery/noMissingThrow
This rule has an unsafe fix.
The default severity of this rule is error.
Sources:
- Inspired from oxc/missing-throw

How to configure

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{
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  "linter": {
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    "rules": {
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      "nursery": {
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        "noMissingThrow": "error"
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      }
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    }
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  }
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}

Description

Disallow creating an error with new without throwing it.

Writing new Error() as a statement, without using its result, creates an error object and then discards it. Nothing happens: the code keeps running as if no error occurred. This is almost always a mistake where the throw keyword was forgotten.

The rule checks constructors whose name starts with an uppercase letter and ends with Error, such as Error, TypeError, or ValidationError.

Examples

Invalid

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function check(value) {
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    if (!value) {
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        new Error("Missing value");
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    }
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}

code-block.js:3:9 lint/nursery/noMissingThrow  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This error is created but never thrown.
  
    1 │ function check(value) {
    2 │     if (!value) {
  > 3 │         new Error("Missing value");
      │         ^^^^^^^^^^^^^^^^^^^^^^^^^^
    4 │     }
    5 │ }
  
  ℹ Creating an error does nothing by itself, so the code keeps running as if nothing went wrong.
  
  ℹ Add the throw keyword to throw the error, or remove the expression if it isn't needed.
  
  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: Add the throw keyword.
  
    3 │ ········throw·new·Error("Missing·value");
      │         ++++++

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const fail = () => {
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    new TypeError("Unexpected type");
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};

code-block.js:2:5 lint/nursery/noMissingThrow  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This error is created but never thrown.
  
    1 │ const fail = () => {
  > 2 │     new TypeError("Unexpected type");
      │     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    3 │ };
    4 │ 
  
  ℹ Creating an error does nothing by itself, so the code keeps running as if nothing went wrong.
  
  ℹ Add the throw keyword to throw the error, or remove the expression if it isn't needed.
  
  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: Add the throw keyword.
  
    2 │ ····throw·new·TypeError("Unexpected·type");
      │     ++++++

Valid

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function check(value) {
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    if (!value) {
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        throw new Error("Missing value");
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    }
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}
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const createError = () => new Error("Something went wrong");
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const error = new Error("Something went wrong");
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reject(new Error("Something went wrong"));