# no-ex-assign

> Disallow assigning to the error parameter of a `catch` clause

Assigning to a `catch` clause's parameter overwrites the error that was caught. From that line on, nothing in the block can read the original message or stack.

This rule is on by default.

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

## Configure

On by default as a warning. To turn it off:

```toml bunfig.toml
[lint.rules]
"no-ex-assign" = "off" # or "error"
```

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

## Examples

Reported:

{/* bad */}
```js
try {
  upload(file);
} catch (error) {
  error = new Error("Upload failed");
  report(error);
}
```

Names that the parameter destructures count as well:

{/* bad */}
```js
try {
  upload(file);
} catch ({ message }) {
  message = "Upload failed";
  report(message);
}
```

Not reported:

{/* good */}
```js
try {
  upload(file);
} catch (error) {
  const wrapped = new Error("Upload failed", { cause: error });
  report(wrapped);
}
```

Setting a property keeps the error, so it's allowed:

{/* good */}
```js
try {
  upload(file);
} catch (error) {
  error.file = file;
  report(error);
}
```