useCatchErrorName (JavaScript)

Language JavaScript (and super languages)

Note

This rule has been implemented but not released yet. It will be available in the next release.

Caution

This rule is part of the nursery group. This means that it is experimental and the behavior can change at any time.

Summary

• Diagnostic Category: lint/nursery/useCatchErrorName
• This rule has an unsafe fix.
• The default severity of this rule is information.
• Sources:
  • Same as unicorn/catch-error-name

How to configure

biome.json

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

Description

Require a specific name for caught errors.

When an error is caught, it is stored in a variable whose name you choose. Using the same name for this variable everywhere makes error handling code easier to read and to search.

The rule checks the variable of:

• try...catch statements;
• functions passed to promise.catch(...);
• functions passed as the second argument of promise.then(..., ...), which handle errors.

The following names are always allowed:

• the configured name, followed by any number of underscores, such as error_. An underscore avoids a clash with another variable of the same name.
• names that end with the configured name, such as fsError or parse_error. These names describe what kind of error is stored.
• _, when the variable is never used.
• names listed in the ignore option.

The fix renames the variable and all its uses. When the configured name is already used by another variable, the fix adds underscores at the end of the name, such as error_.

Examples

Invalid

try {} catch (err) {}

code-block.js:1:15 lint/nursery/useCatchErrorName  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ The caught error is named err instead of error.
  
  > 1 │ try {} catch (err) {}
      │               ^^^
    2 │ 
  
  ℹ Using the same name for caught errors everywhere makes error handling code easier to read and search.
  
  ℹ Rename the variable to error.
  
  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: Rename the variable to error.
  
    1   │ - try·{}·catch·(err)·{}
      1 │ + try·{}·catch·(error)·{}
    2 2 │   
  

promise.catch((e) => {});

code-block.js:1:16 lint/nursery/useCatchErrorName  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ The caught error is named e instead of error.
  
  > 1 │ promise.catch((e) => {});
      │                ^
    2 │ 
  
  ℹ Using the same name for caught errors everywhere makes error handling code easier to read and search.
  
  ℹ Rename the variable to error.
  
  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: Rename the variable to error.
  
    1   │ - promise.catch((e)·=>·{});
      1 │ + promise.catch((error)·=>·{});
    2 2 │   
  

promise.then(undefined, function (reason) {});

code-block.js:1:35 lint/nursery/useCatchErrorName  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ The caught error is named reason instead of error.
  
  > 1 │ promise.then(undefined, function (reason) {});
      │                                   ^^^^^^
    2 │ 
  
  ℹ Using the same name for caught errors everywhere makes error handling code easier to read and search.
  
  ℹ Rename the variable to error.
  
  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: Rename the variable to error.
  
    1   │ - promise.then(undefined,·function·(reason)·{});
      1 │ + promise.then(undefined,·function·(error)·{});
    2 2 │   
  

try {} catch (_) {
    console.log(_);
}

code-block.js:1:15 lint/nursery/useCatchErrorName  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ The caught error is named _ instead of error.
  
  > 1 │ try {} catch (_) {
      │               ^
    2 │     console.log(_);
    3 │ }
  
  ℹ Using the same name for caught errors everywhere makes error handling code easier to read and search.
  
  ℹ Rename the variable to error.
  
  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: Rename the variable to error.
  
    1   │ - try·{}·catch·(_)·{
    2   │ - ····console.log(_);
      1 │ + try·{}·catch·(error)·{
      2 │ + ····console.log(error);
    3 3 │   }
    4 4 │   
  

Valid

try {} catch (error) {}

promise.catch((error) => {});

promise.then(undefined, function (error) {});

try {} catch (_) {}

try {} catch (fsError) {}

try {} catch (error_) {
    const error = new Error("Something went wrong");
}

Options

name

Default: "error"

The required name of caught errors.

biome.json

{
  "linter": {
    "rules": {
      "nursery": {
        "useCatchErrorName": {
          "level": "on",
          "options": {
            "name": "exception"
          }
        }
      }
    }
  }
}

Invalid

try {} catch (error) {}

code-block.js:1:15 lint/nursery/useCatchErrorName  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ The caught error is named error instead of exception.
  
  > 1 │ try {} catch (error) {}
      │               ^^^^^
    2 │ 
  
  ℹ Using the same name for caught errors everywhere makes error handling code easier to read and search.
  
  ℹ Rename the variable to exception.
  
  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: Rename the variable to exception.
  
    1   │ - try·{}·catch·(error)·{}
      1 │ + try·{}·catch·(exception)·{}
    2 2 │   
  

Valid

try {} catch (exception) {}

ignore

Default: []

A list of names that are always allowed, in addition to the configured name.

biome.json

{
  "linter": {
    "rules": {
      "nursery": {
        "useCatchErrorName": {
          "level": "on",
          "options": {
            "ignore": [
              "exception"
            ]
          }
        }
      }
    }
  }
}

try {} catch (exception) {}

Related links

• Disable a rule
• Configure the code fix
• Rule options
• Source Code (Edit this Page)
• Test Cases
• Try in the playground