Suppressions

The Biome analyzer is the foundation of the linter and assist; in fact, both tools share a lot of similarities.

Among them, they share the same suppression engine, which means that you can suppress a lint rule the same way you would suppress an assist action.

With suppression, it's possible to turn off a lint rule (or action) for a specific line of code, a range, or the entire file.

Suppression is achievable with suppression comments.

Suppression syntax

Suppression comments have the following format:

// biome-ignore lint: <explanation>
// biome-ignore assist: <explanation>
// biome-ignore syntax: <explanation>
// biome-ignore lint/suspicious: <explanation>
// biome-ignore lint/suspicious/noDebugger: <explanation>
// biome-ignore lint/suspicious/noDebugger(foo): <explanation>
// biome-ignore-all lint: <explanation>
// biome-ignore-start lint: <explanation>
// biome-ignore-end lint: <explanation>

Let's break it down:

• biome-ignore, biome-ignore-all, biome-ignore-start and biome-ignore-end are the start of a suppression comment.
• After the space follows the category of the suppression comment. It can be lint, assist, or syntax.
• The category is followed by an optional group, or group and name, separated by slashes. For example, /suspicious or /suspicious/noDebugger. The more you specify, the more specific (i.e. targeted) your suppression is.
• Some rules even allow you to specify values during suppression. These can be specified between parentheses, for example: (foo). Refer to the rule documentation to see whether a rule supports suppression with values.
• <explanation> explanation why the rule is disabled.

If you're unsure of the exact category of a rule/action, you can refer to their documentation page and use their diagnostic category.

:::note From here onwards, JavaScript is used to explain suppression comments, and the lint category is used. :::

Inline suppressions

They disable a lint rule for the next line of code.

In the following example, the suppression comment biome-ignore lint/suspicious/noDebugger: reason will disable the debugger; statement at line 2, but the debugger at line 3 will still raise a diagnostic:

// biome-ignore lint/suspicious/noDebugger: reason
debugger;
debugger;

Top-level suppressions

They disable a lint rule for an entire file. They must be placed at the top of the file, and they must start with biome-ignore-all.

These suppression comments are very useful when you want to suppress some lint rule for a particular file, and you don't want to rely on a single configuration override to achieve that.

In the following example, the suppression comment biome-ignore-all lint/suspicious/noDebugger: reason will disable the lint rule for all lines in generated.js:

// biome-ignore-all lint/suspicious/noDebugger: reason
debugger;
debugger;

When a top-level suppression comment isn't at the top of the file, it is considered unused and Biome will emit a diagnostic with category suppression/unused.

Range suppressions

They disable a lint rule from a particular range in the file, starting from the line with the start comment, until the line with the end comment.

To mark the beginning of a range suppression, the suppression comment must start with // biome-ignore-start. To mark the end of it, the suppression comment must start with // biome-ignore-end.

The following example will disable the rule lint/suspicious/noDoubleEquals for line 2 and 3, but line 5 will raise a diagnostic:

// biome-ignore-start lint/suspicious/noDoubleEquals: reason
a == b;
c == d;
// biome-ignore-end lint/suspicious/noDoubleEquals: reason
f == g;

:::note Range suppressions must have a matching biome-ignore-end suppression. :::

Range suppressions can also overlap. Consider the following example:

debugger;
// biome-ignore-start lint/suspicious/noDebugger: reason
debugger;
// biome-ignore-start lint/suspicious/noDoubleEquals: reason
a == b;
c == d;
// biome-ignore-end lint/suspicious/noDoubleEquals: reason
debugger;
f == g;
// biome-ignore-end lint/suspicious/noDebugger: reason

In the above code:

• The debugger statement at line 1 will raise a diagnostic because there's no suppression comment that disables it.
• The comment // biome-ignore-start lint/suspicious/noDebugger: reason at line 2 starts disabling noDebugger from line 3 onwards.
• The comment // biome-ignore-start lint/suspicious/noDoubleEquals: reason at line 4 starts disabling noDoubleEquals from line 5 onwards.
• The comment // biome-ignore-end lint/suspicious/noDoubleEquals: reason at line 7 terminates the suppression of noDoubleEquals that was started by the suppression comment at line 4.
• The debugger statement at line 8 doesn't raise diagnostics due to the suppression comment at line 2.
• The f == g statement raises a diagnostic because the rule noDoubleEquals isn't suppressed anymore.
• The comment // biome-ignore-end lint/suspicious/noDebugger: reason at line 10 terminates the suppression of noDebugger that was started by the suppression comment at line 2.