oxc-project/oxc · warning · OxcDiagnostic

No magic number: {raw}

Error message

No magic number: {raw}

What it means

Diagnostic from oxlint's eslint/no-magic-numbers rule (crates/oxc_linter/src/rules/eslint/no_magic_numbers.rs:27). It reports a bare numeric literal used where its meaning is not obvious — comparisons, assignments, arguments, indices — with the raw literal text included in the message (e.g. 'No magic number: 86.4'). Common defaults like -1, 0, 1, 2 are ignored, and the rule offers ignore lists plus toggles such as ignoreArrayIndexes, ignoreDefaultValues, detectObjects, and the TypeScript-specific ignore flags.

Source

Thrown at crates/oxc_linter/src/rules/eslint/no_magic_numbers.rs:27

use oxc_syntax::operator::UnaryOperator;
use schemars::JsonSchema;
use serde::{Deserialize, Serialize};

use crate::{AstNode, ast_util::variable_declaration_kind, context::LintContext, rule::Rule};

enum NoMagicNumberReportReason {
    MustUseConst,
    NoMagicNumber,
}

fn must_use_const_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Number constants declarations must use 'const'.")
        .with_help("Use 'const' instead of 'let' or 'var' to declare number constants to make their immutability explicit.")
        .with_label(span)
}

fn no_magic_number_diagnostic(span: Span, raw: &str) -> OxcDiagnostic {
    OxcDiagnostic::warn(format!("No magic number: {raw}"))
        .with_help("Use a named constant instead of a magic number to make the code more readable and maintainable.")
        .with_label(span)
}

#[derive(Debug, Default, Clone)]
pub struct NoMagicNumbers(Box<NoMagicNumbersConfig>);

impl std::ops::Deref for NoMagicNumbers {
    type Target = NoMagicNumbersConfig;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

#[derive(Debug, Clone, PartialEq, Serialize, Deserialize, JsonSchema)]
#[serde(untagged)]
pub enum NoMagicNumbersNumber {

View on GitHub (pinned to e1e7af627c)

Solutions

1. Extract the literal into a named constant at module scope: const HTTP_NOT_FOUND = 404; if (res.status === HTTP_NOT_FOUND)
2. For values that are intentionally inline (unit tests, configuration tables), add them to the "ignore" array or enable the relevant skip options (ignoreArrayIndexes, ignoreDefaultValues, ignoreEnums, ignoreTypeIndexes, ...)
3. For large migrations, disable the rule per-directory via .oxlintrc.json overrides and fix hotspots first

Example fix

// before
if (res.status === 404) return notFound();
setTimeout(poll, 30000);

// after
const HTTP_NOT_FOUND = 404;
const POLL_INTERVAL_MS = 30_000;
if (res.status === HTTP_NOT_FOUND) return notFound();
setTimeout(poll, POLL_INTERVAL_MS);

When it happens

Trigger: if (res.status === 404) {...}; const timeout = 30000;; data[3] used as a fixed index; new Array(5). Numeric literals in test assertions and class field initializers are also checked unless the corresponding ignore options are set.

Common situations: Enabling no-magic-numbers in a shared config (airbnb-style) and running it over an existing codebase for the first time; numeric status/error codes in HTTP and protocol handling; hardware/register code full of protocol constants.

Related errors

• Unexpected `if` as the only statement in an `else` block
• Number constants declarations must use 'const'.
• Unnecessary `else` after `return`.
• Found identifier '{name}' with the same name as a label.
• Labeled statement is not allowed

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/3f6d20799261ddd0. Report an issue: GitHub.