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merged 3 commits into from
Sep 2, 2025
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refactor(eslint/default-case): simplify implementation and enhance readability #13430

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refactor(eslint/default-case): simplify implementation and enhance re…
antoinezanardi Aug 30, 2025
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docs(default_case): format commentPattern for improved clarity
antoinezanardi Aug 30, 2025
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docs(default_case): update examples to remove redundant comments for …
antoinezanardi Sep 2, 2025
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136 changes: 72 additions & 64 deletions crates/oxc_linter/src/rules/eslint/default_case.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,79 +31,80 @@ impl std::ops::Deref for DefaultCase {
declare_oxc_lint!(
/// ### What it does
///
/// Require default cases in switch statements
/// Enforces that all `switch` statements include a `default` case,
/// unless explicitly marked with a configured comment.
///
/// ### Why is this bad?
///
/// Some code conventions require that all switch statements have a default case,
/// even if the default case is empty. The thinking is that it’s better to always
/// explicitly state what the default behavior should be so that it’s clear
/// whether or not the developer forgot to include the default behavior by mistake.
/// Without a `default` case, it is unclear whether the omission was
/// intentional or an oversight. Adding a `default` or a special comment
/// makes the code more explicit and reduces mistakes.
///
/// You may optionally include a `// no default` after the last case if there is
/// no default case. The comment may be in any desired case, such as `// No Default`.
///
/// ### Examples
/// ### Options
///
/// First option:
/// - Type: `object`
/// - Properties:
/// - `commentPattern`: `string` (default: `/^no default$/i`) - A regex pattern used to detect comments that mark the absence of a `default` case as intentional.
///
/// Example configuration:
/// ```json
/// {
/// "default-case": ["error", { "commentPattern": "^skip\\sdefault" }]
/// }
/// ```
///
/// Examples of **incorrect** code for this rule:
/// ```javascript
/// ```js
/// /* default-case: ["error"] */
///
/// switch (foo) {
/// case 1:
/// break;
/// }
/// ```
///
/// Examples of **correct** code for this rule:
/// ```javascript
/// ```js
/// /* default-case: ["error"] */
///
/// switch (a) {
/// case 1:
/// /* code */
/// break;
///
/// default:
/// /* code */
/// break;
/// }
/// ```
///
/// ```javascript
/// switch (a) {
/// case 1:
/// /* code */
/// break;
///
/// // no default
/// }
/// ```
///
/// ```javascript
/// #### `commentPattern`
///
/// Examples of **incorrect** code for this rule with the `{ "commentPattern": "^skip\\sdefault" }` option:
/// ```js
/// /* default-case: ["error", { "commentPattern": "^skip\\sdefault" }] */
///
/// switch (a) {
/// case 1:
/// /* code */
/// break;
///
/// // No Default
/// // no default
/// }
/// ```
///
/// ### Options
///
/// #### commentPattern
///
/// `{ type: string, default: "/^no default$/i" }`
/// Examples of **correct** code for this rule with the `{ "commentPattern": "^skip\\sdefault" }` option:
/// ```js
/// /* default-case: ["error", { "commentPattern": "^skip\\sdefault" }] */
///
/// This option is for specifying an alternative regular expression which
/// will override the default `/^no default$/i` comment test pattern.
///
/// For example if `{ "commentPattern": "^skip\\sdefault" }` were used
/// then the following example would not violate the rule:
///
/// ```javascript
/// switch(a) {
/// switch (a) {
/// case 1:
/// /* code */
/// break;
///
/// // skip default
/// }
/// ```
Expand All @@ -114,48 +115,55 @@ declare_oxc_lint!(

impl Rule for DefaultCase {
fn from_configuration(value: serde_json::Value) -> Self {
let mut cfg = DefaultCaseConfig::default();

if let Some(config) = value.get(0) {
if let Some(val) = config.get("commentPattern").and_then(serde_json::Value::as_str) {
cfg.comment_pattern = RegexBuilder::new(val).case_insensitive(true).build().ok();
}
}
let comment_pattern = value
.get(0)
.and_then(|config| config.get("commentPattern"))
.and_then(serde_json::Value::as_str)
.and_then(|pattern| RegexBuilder::new(pattern).case_insensitive(true).build().ok());
let case_config = DefaultCaseConfig { comment_pattern };

Self(Box::new(cfg))
Self(Box::new(case_config))
}

fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
if let AstKind::SwitchStatement(switch) = node.kind() {
let cases = &switch.cases;
let AstKind::SwitchStatement(switch) = node.kind() else {
return;
};

if cases.is_empty() || cases.iter().any(|case| case.test.is_none()) {
return;
}
let cases = &switch.cases;

let Some(last_case) = cases.last() else {
return;
};
if cases.is_empty() || cases.iter().any(|case| case.test.is_none()) {
return;
}

let has_default_comment = ctx
.semantic()
.comments_range(last_case.span.start..switch.span.end)
.next_back()
.is_some_and(|comment| {
let raw = ctx.source_range(comment.content_span()).trim();
match &self.comment_pattern {
Some(comment_pattern) => comment_pattern.is_match(raw),
None => raw.eq_ignore_ascii_case("no default"),
}
});
let Some(last_case) = cases.last() else {
return;
};

if !has_default_comment {
ctx.diagnostic(default_case_diagnostic(switch.span));
}
if !has_default_comment(ctx, switch.span, last_case.span, self.comment_pattern.as_ref()) {
ctx.diagnostic(default_case_diagnostic(switch.span));
}
}
}

fn has_default_comment(
ctx: &LintContext,
switch_span: Span,
last_case_span: Span,
comment_pattern: Option<&Regex>,
) -> bool {
ctx.semantic().comments_range(last_case_span.start..switch_span.end).next_back().is_some_and(
|comment| {
let raw = ctx.source_range(comment.content_span()).trim();

match comment_pattern {
Some(re) => re.is_match(raw),
None => raw.eq_ignore_ascii_case("no default"),
}
},
)
}

#[test]
fn test() {
use crate::tester::Tester;
Expand Down
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