# unicorn/catch-error-name

> Enforce one name for the error in `catch` clauses and promise handlers

When one file catches `e`, the next `err` and a third `ex`, you need to look up the name every time you read or move a `catch` block. With this rule the caught error is always called `error`.

The rule checks `catch` clauses, the first parameter of a function passed to `.catch()`, and the first parameter of the second function passed to `.then()`.

`--fix` renames the parameter and every use of it.

{/* Generated by src/codegen/lint-rule-docs.ts. Do not edit this section. */}

## Configure

Off by default. To turn it on:

```toml bunfig.toml
[lint.rules]
"unicorn/catch-error-name" = "error" # or "warn"
```

Every option, set to its default:

```toml bunfig.toml
[lint.rules]
"unicorn/catch-error-name" = ["error", {
  name = "error",
  ignore = [], # list of strings
}]
```

{/* End of the generated section. */}

## Examples

Reported:

{/* bad {"count": 3} */}
```js
try {
  await save(user);
} catch (e) {
  console.log(e.message);
}

save(user).catch(err => console.log(err.message));

save(user).then(done, ex => console.log(ex.message));
```

Not reported:

{/* good */}
```js
try {
  await save(user);
} catch (error) {
  console.log(error.message);
}

save(user).catch(error => console.log(error.message));

save(user).then(done, error => console.log(error.message));
```

A name that ends in `error` is fine, such as `saveError`, or `error_` in a nested `catch`. So is a name that starts with `_`, as long as the error isn't used.

{/* good */}
```js
try {
  await save(user);
} catch (saveError) {
  try {
    await rollback();
  } catch (error_) {
    report(saveError, error_);
  }
}

save(user).catch(_ => retry());
```

## Options

| Option | Default | What it does |
| --- | --- | --- |
| `name` | `"error"` | The name to require. A value that isn't a valid identifier is ignored. |
| `ignore` | `[]` | Regular expressions, as strings. A name that matches one of them is allowed. |

{/* good {"options": [{"name": "err"}]} */}
```js
save(user).catch(err => console.log(err.message));
```

{/* good {"options": [{"ignore": ["^reason$"]}]} */}
```js
save(user).catch(reason => console.log(reason));
```