oxc-project/oxc · warning · OxcDiagnostic

Require `default` cases in `switch` statements.

Error message

Require `default` cases in `switch` statements.

What it means

Oxlint's port of the ESLint rule default-case: every `switch` statement must contain a `default` clause. The diagnostic is default_case_diagnostic (crates/oxc_linter/src/rules/eslint/default_case.rs:16) with help 'Add a `default` case.' DefaultCaseConfig carries `commentPattern`, a regex; when a comment inside the switch matches it, the missing default is treated as intentional and not reported.

Source

Thrown at crates/oxc_linter/src/rules/eslint/default_case.rs:17

use lazy_regex::{Regex, RegexBuilder};
use schemars::JsonSchema;
use serde::Deserialize;

use oxc_ast::AstKind;
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_span::Span;

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

fn default_case_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Require `default` cases in `switch` statements.")
        .with_help("Add a `default` case.")
        .with_label(span)
}

#[derive(Debug, Default, Clone, Deserialize)]
pub struct DefaultCase(Box<DefaultCaseConfig>);

#[derive(Debug, Default, Clone, Deserialize, JsonSchema)]
#[serde(rename_all = "camelCase", default, deny_unknown_fields)]
pub struct DefaultCaseConfig {
    /// A regex pattern used to detect comments that mark the absence
    /// of a `default` case as intentional.
    ///
    /// Default value: `no default`.
    ///
    /// Examples of **incorrect** code for this rule with the `{ "commentPattern": "^skip\\sdefault" }` option:
    /// ```js
    /// switch (a) {

View on GitHub (pinned to e1e7af627c)

Solutions

1. Add an explicit default clause to the switch, even a throwing or no-op one.
2. If omitting default is intentional, add a comment that matches the configured commentPattern, e.g. `// no default`.
3. Configure commentPattern in .oxlintrc.json to your team's marker comment.
4. Disable the rule when exhaustiveness is already enforced by TypeScript's never check.

Example fix

// before
switch (kind) {
  case 'a': return 1;
  case 'b': return 2;
}

// after
switch (kind) {
  case 'a': return 1;
  case 'b': return 2;
  default:
    throw new Error(kind);
}

// .oxlintrc.json — configure the intentional-omission marker comment
{
  "rules": {
    "default-case": ["warn", { "commentPattern": "^no default$" }]
  }
}

When it happens

Trigger: Linting any switch that has case clauses but no default clause and no comment matching the configured commentPattern (unset by default, so any comment opt-out requires configuring the pattern).

Common situations: Switches over enums believed to be exhaustive; migrating an ESLint config whose commentPattern (e.g. "^no default$") was not carried over; teammates unaware of the comment-based opt-out.

Related errors

• Enforce default clauses in switch statements to be last
• Expected a `break` statement before `case`.
• Expected a `break` statement before `default`.
• Found a comment that would permit fallthrough, but case cann
• Checking `switch` discriminant against NaN will never match

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/b4dc563d24704969. Report an issue: GitHub.