# A catch that only rethrows; logging an error and rethrowing it

*Code longer than it needs to be*: one of the ways AI coding agents bloat software, from lessloc's [pattern catalog](https://lessloc.org/patterns/index.md). lessloc catches it as [`simpler`](https://lessloc.org/guide/reference.md#tier-2).

## What makes a catch that only rethrows a bad practice?

The standards that call it a bad practice: ESLint no-useless-catch; Sonar S2737; ruff TRY203; McCune, "Exception-Handling Antipatterns": Log and Throw.

## What does lessloc do about a catch that only rethrows?

lessloc catches it as [`simpler`](https://lessloc.org/guide/reference.md#tier-2).

- `simpler` (tier 2): Brute-force code with a shorter idiom: `== True`, an if/else that returns the condition, an index loop that only reads `xs[i]`, `.filter(...).length > 0`, a catch that only rethrows, a flag loop that is `any()`, a hand-built counter, an `__init__` that `@dataclass` writes, a React Effect that only sets state. ruff and clippy add more.

## Examples

Caught as `simpler`:

```js [s.js]
export async function load(f) {
  try {
    return await f();
  } catch (e) {
    throw e;
  }
}
```

Written well:

```js [s.js]
export async function load(f) {
  return f();
}
```

Caught as `simpler`:

```js [t.js]
export async function load(f) {
  try {
    return await f();
  } catch (err) {
    console.error("load failed", err);
    throw err;
  }
}
```

Written well:

```js [t.js]
export async function load(f) {
  try {
    return await f();
  } catch (err) {
    throw new Error("load failed", { cause: err });
  }
}
```

## Related patterns

The other patterns in [Code longer than it needs to be](https://lessloc.org/patterns/index.md#code-longer-than-it-needs-to-be):

- [Brute-force idioms](https://lessloc.org/patterns/brute-force.md): lessloc catches it as `simpler`, built in for Python, JS/TS, Go, Rust, Java and C#. ruff (in every hook) and clippy (in `ci`) go deeper.
- [Hand-built counters and flag loops](https://lessloc.org/patterns/counters-and-flags.md): lessloc catches it as `simpler`.
- [A promise wrapped in new Promise](https://lessloc.org/patterns/promise-wrap.md): lessloc catches it as `simpler`.
- [Annotating types the compiler infers](https://lessloc.org/patterns/inferred-types.md): lessloc catches it as `simpler`.
- [A React Effect that only sets state from other values](https://lessloc.org/patterns/derived-effect.md): lessloc catches it as `simpler`.
- [Functions with many parameters (8 or more)](https://lessloc.org/patterns/long-params.md): lessloc catches it as `long-params`.
- [Deep nesting](https://lessloc.org/patterns/deep-nesting.md): lessloc catches it as `deep-nesting`.
- [Long functions](https://lessloc.org/patterns/long-function.md): lessloc catches it as `long-function`.
- [If-chains on literal values](https://lessloc.org/patterns/if-chain.md): lessloc catches it as `if-chain`.
- [A file that keeps growing](https://lessloc.org/patterns/swollen-file.md): lessloc catches it as `swollen-file`.
- [Reformatting lines the task did not change](https://lessloc.org/patterns/churn.md): lessloc gives every session a rule against it and catches it as `churn`.
- [Net growth past a budget](https://lessloc.org/patterns/net-growth.md): lessloc catches it as `net-growth`.
- [Golfed code](https://lessloc.org/patterns/golfed-code.md): lessloc catches it as `clever` and `dense-lines`.