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noUselessCatch

src/content/docs/linter/rules/no-useless-catch.mdx

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import { Tabs, TabItem } from '@astrojs/starlight/components';

<Tabs> <TabItem label="JavaScript (and super languages)" icon="seti:javascript"> ## Summary - Rule available since: `v1.0.0` - Diagnostic Category: [`lint/complexity/noUselessCatch`](/reference/diagnostics#diagnostic-category) - This rule is **recommended**, meaning it is enabled by default. - This rule has an [**unsafe**](/linter/#unsafe-fixes) fix. - The default severity of this rule is [**information**](/reference/diagnostics#information). - Sources: - Same as [`no-useless-catch`](https://eslint.org/docs/latest/rules/no-useless-catch)

How to configure

json
{
	"linter": {
		"rules": {
			"complexity": {
				"noUselessCatch": "error"
			}
		}
	}
}

Description

Disallow unnecessary catch clauses.

A catch clause that only rethrows the original error is redundant, and has no effect on the runtime behavior of the program. These redundant clauses can be a source of confusion and code bloat, so it’s better to disallow these unnecessary catch clauses.

Examples

Invalid

js
try {
    doSomething();
} catch(e) {
    throw e;
}
<pre class="language-text"><code class="language-text">code-block.js:4:5 <a href="https://biomejs.dev/linter/rules/no-useless-catch">lint/complexity/noUselessCatch</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">The </span><span style="color: lightgreen;"><strong>catch</strong></span><span style="color: lightgreen;"> clause that only rethrows the original error is useless.</span> <strong>2 │ </strong> doSomething(); <strong>3 │ </strong>&#125; catch(e) &#123; <strong><span style="color: Tomato;">&gt;</span></strong> <strong>4 │ </strong> throw e; <strong> │ </strong> <strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong> <strong>5 │ </strong>&#125; <strong>6 │ </strong> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">An unnecessary </span><span style="color: lightgreen;"><strong>catch</strong></span><span style="color: lightgreen;"> clause can be confusing.</span> </code></pre>
js
try {
    doSomething();
} catch(e) {
    throw e;
} finally {
    doCleanUp();
}
<pre class="language-text"><code class="language-text">code-block.js:4:5 <a href="https://biomejs.dev/linter/rules/no-useless-catch">lint/complexity/noUselessCatch</a> <span style="color: #000; background-color: #ddd;"> FIXABLE </span> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">The </span><span style="color: lightgreen;"><strong>catch</strong></span><span style="color: lightgreen;"> clause that only rethrows the original error is useless.</span> <strong>2 │ </strong> doSomething(); <strong>3 │ </strong>&#125; catch(e) &#123; <strong><span style="color: Tomato;">&gt;</span></strong> <strong>4 │ </strong> throw e; <strong> │ </strong> <strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong> <strong>5 │ </strong>&#125; finally &#123; <strong>6 │ </strong> doCleanUp(); <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">An unnecessary </span><span style="color: lightgreen;"><strong>catch</strong></span><span style="color: lightgreen;"> clause can be confusing.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Unsafe fix</span><span style="color: lightgreen;">: </span><span style="color: lightgreen;">Remove the </span><span style="color: lightgreen;"><strong>catch</strong></span><span style="color: lightgreen;"> clause.</span> <strong>1</strong> <strong>1</strong><strong> │ </strong> try &#123; <strong>2</strong> <strong>2</strong><strong> │ </strong> doSomething(); <strong>3</strong> <strong> │ </strong><span style="color: Tomato;">-</span> <span style="color: Tomato;">&#125;</span><span style="color: Tomato;"><span style="opacity: 0.8;">·</span></span><span style="color: Tomato;"><strong>c</strong></span><span style="color: Tomato;"><strong>a</strong></span><span style="color: Tomato;"><strong>t</strong></span><span style="color: Tomato;"><strong>c</strong></span><span style="color: Tomato;"><strong>h</strong></span><span style="color: Tomato;"><strong>(</strong></span><span style="color: Tomato;"><strong>e</strong></span><span style="color: Tomato;"><strong>)</strong></span><span style="color: Tomato;"><span style="opacity: 0.8;"><strong>·</strong></span></span><span style="color: Tomato;"><strong>&#123;</strong></span> <strong>4</strong> <strong> │ </strong><span style="color: Tomato;">-</span> <span style="color: Tomato;"><span style="opacity: 0.8;"><strong>·</strong></span></span><span style="color: Tomato;"><span style="opacity: 0.8;"><strong>·</strong></span></span><span style="color: Tomato;"><span style="opacity: 0.8;"><strong>·</strong></span></span><span style="color: Tomato;"><span style="opacity: 0.8;"><strong>·</strong></span></span><span style="color: Tomato;"><strong>t</strong></span><span style="color: Tomato;"><strong>h</strong></span><span style="color: Tomato;"><strong>r</strong></span><span style="color: Tomato;"><strong>o</strong></span><span style="color: Tomato;"><strong>w</strong></span><span style="color: Tomato;"><span style="opacity: 0.8;"><strong>·</strong></span></span><span style="color: Tomato;"><strong>e</strong></span><span style="color: Tomato;"><strong>;</strong></span> <strong>5</strong> <strong> │ </strong><span style="color: Tomato;">-</span> <span style="color: Tomato;"><strong>&#125;</strong></span><span style="color: Tomato;"><span style="opacity: 0.8;"><strong>·</strong></span></span><span style="color: Tomato;">f</span><span style="color: Tomato;">i</span><span style="color: Tomato;">n</span><span style="color: Tomato;">a</span><span style="color: Tomato;">l</span><span style="color: Tomato;">l</span><span style="color: Tomato;">y</span><span style="color: Tomato;"><span style="opacity: 0.8;">·</span></span><span style="color: Tomato;">&#123;</span> <strong>3</strong><strong> │ </strong><span style="color: MediumSeaGreen;">+</span> <span style="color: MediumSeaGreen;">&#125;</span><span style="color: MediumSeaGreen;"><span style="opacity: 0.8;">·</span></span><span style="color: MediumSeaGreen;">f</span><span style="color: MediumSeaGreen;">i</span><span style="color: MediumSeaGreen;">n</span><span style="color: MediumSeaGreen;">a</span><span style="color: MediumSeaGreen;">l</span><span style="color: MediumSeaGreen;">l</span><span style="color: MediumSeaGreen;">y</span><span style="color: MediumSeaGreen;"><span style="opacity: 0.8;">·</span></span><span style="color: MediumSeaGreen;">&#123;</span> <strong>6</strong> <strong>4</strong><strong> │ </strong> doCleanUp(); <strong>7</strong> <strong>5</strong><strong> │ </strong> &#125; </code></pre>

Valid

js
try {
    doSomething();
} catch(e) {
    doSomethingWhenCatch();
    throw e;
}
js
try {
    doSomething();
} catch(e) {
    handleError(e);
}
js
try {
    doSomething();
} finally {
    doCleanUp();
}
</TabItem> </Tabs>