feat(es/lints): Add default-case-last rule (#4913)

crates/swc/tests/errors/lints/default-case-last/default/.swcrc

@@ -0,0 +1,9 @@
+{
+    "jsc": {
+        "lints": {
+            "default-case-last": [
+                "error"
+            ]
+        }
+    }
+}

crates/swc/tests/errors/lints/default-case-last/default/input.js

@@ -0,0 +1,39 @@
+switch (foo) { default: bar(); break; case 1: baz(); break; }
+switch (foo) { default: break; case 1: break; }
+switch (foo) { default: break; case 1: }
+switch (foo) { default: case 1: break; }
+switch (foo) { default: case 1: }
+switch (foo) { default: break; case 1: break; case 2: break; }
+switch (foo) { default: case 1: break; case 2: break; }
+switch (foo) { default: case 1: case 2: break; }
+switch (foo) { default: case 1: case 2: }
+switch (foo) { case 1: break; default: break; case 2: break; }
+switch (foo) { case 1: default: break; case 2: break; }
+switch (foo) { case 1: break; default: case 2: break; }
+switch (foo) { case 1: default: case 2: break; }
+switch (foo) { case 1: default: case 2: }
+
+// valid
+switch (foo) { }
+switch (foo) { case 1: bar(); break; }
+switch (foo) { case 1: break; }
+switch (foo) { case 1: }
+switch (foo) { case 1: bar(); break; case 2: baz(); break; }
+switch (foo) { case 1: break; case 2: break; }
+switch (foo) { case 1: case 2: break; }
+switch (foo) { case 1: case 2: }
+switch (foo) { default: bar(); break; }
+switch (foo) { default: bar(); }
+switch (foo) { default: break; }
+switch (foo) { default: }
+switch (foo) { case 1: break; default: break; }
+switch (foo) { case 1: break; default: }
+switch (foo) { case 1: default: break; }
+switch (foo) { case 1: default: }
+switch (foo) { case 1: baz(); break; case 2: quux(); break; default: quuux(); break; }
+switch (foo) { case 1: break; case 2: break; default: break; }
+switch (foo) { case 1: break; case 2: break; default: }
+switch (foo) { case 1: case 2: break; default: break; }
+switch (foo) { case 1: break; case 2: default: break; }
+switch (foo) { case 1: break; case 2: default: }
+switch (foo) { case 1: case 2: default: }

crates/swc/tests/errors/lints/default-case-last/default/output.swc-stderr

@@ -0,0 +1,84 @@
+
+  x Default clause should be the last clause
+   ,----
+ 1 | switch (foo) { default: bar(); break; case 1: baz(); break; }
+   :                ^^^^^^^^^^^^^^^^^^^^^^
+   `----
+
+  x Default clause should be the last clause
+   ,----
+ 2 | switch (foo) { default: break; case 1: break; }
+   :                ^^^^^^^^^^^^^^^
+   `----
+
+  x Default clause should be the last clause
+   ,----
+ 3 | switch (foo) { default: break; case 1: }
+   :                ^^^^^^^^^^^^^^^
+   `----
+
+  x Default clause should be the last clause
+   ,----
+ 4 | switch (foo) { default: case 1: break; }
+   :                ^^^^^^^^
+   `----
+
+  x Default clause should be the last clause
+   ,----
+ 5 | switch (foo) { default: case 1: }
+   :                ^^^^^^^^
+   `----
+
+  x Default clause should be the last clause
+   ,----
+ 6 | switch (foo) { default: break; case 1: break; case 2: break; }
+   :                ^^^^^^^^^^^^^^^
+   `----
+
+  x Default clause should be the last clause
+   ,----
+ 7 | switch (foo) { default: case 1: break; case 2: break; }
+   :                ^^^^^^^^
+   `----
+
+  x Default clause should be the last clause
+   ,----
+ 8 | switch (foo) { default: case 1: case 2: break; }
+   :                ^^^^^^^^
+   `----
+
+  x Default clause should be the last clause
+   ,----
+ 9 | switch (foo) { default: case 1: case 2: }
+   :                ^^^^^^^^
+   `----
+
+  x Default clause should be the last clause
+    ,----
+ 10 | switch (foo) { case 1: break; default: break; case 2: break; }
+    :                               ^^^^^^^^^^^^^^^
+    `----
+
+  x Default clause should be the last clause
+    ,----
+ 11 | switch (foo) { case 1: default: break; case 2: break; }
+    :                        ^^^^^^^^^^^^^^^
+    `----
+
+  x Default clause should be the last clause
+    ,----
+ 12 | switch (foo) { case 1: break; default: case 2: break; }
+    :                               ^^^^^^^^
+    `----
+
+  x Default clause should be the last clause
+    ,----
+ 13 | switch (foo) { case 1: default: case 2: break; }
+    :                        ^^^^^^^^
+    `----
+
+  x Default clause should be the last clause
+    ,----
+ 14 | switch (foo) { case 1: default: case 2: }
+    :                        ^^^^^^^^
+    `----

crates/swc_ecma_lints/src/config.rs

@@ -199,4 +199,8 @@ pub struct LintConfig {
     #[cfg(feature = "non_critical_lints")]
     #[serde(default, alias = "noSparseArrays")]
     pub no_sparse_arrays: RuleConfig<()>,
+
+    #[cfg(feature = "non_critical_lints")]
+    #[serde(default, alias = "defaultCaseLast")]
+    pub default_case_last: RuleConfig<()>,
 }

crates/swc_ecma_lints/src/rules/default_case_last.rs

@@ -0,0 +1,66 @@
+use swc_common::{errors::HANDLER, Span};
+use swc_ecma_ast::*;
+use swc_ecma_visit::{Visit, VisitWith};
+
+use crate::{
+    config::{LintRuleReaction, RuleConfig},
+    rule::{visitor_rule, Rule},
+};
+
+const MESSAGE: &str = "Default clause should be the last clause";
+
+pub fn default_case_last(config: &RuleConfig<()>) -> Option<Box<dyn Rule>> {
+    let rule_reaction = config.get_rule_reaction();
+
+    match rule_reaction {
+        LintRuleReaction::Off => None,
+        _ => Some(visitor_rule(DefaultCaseLast::new(rule_reaction))),
+    }
+}
+
+#[derive(Debug, Default)]
+struct DefaultCaseLast {
+    expected_reaction: LintRuleReaction,
+}
+
+impl DefaultCaseLast {
+    fn new(expected_reaction: LintRuleReaction) -> Self {
+        Self { expected_reaction }
+    }
+
+    fn emit_report(&self, span: Span) {
+        HANDLER.with(|handler| match self.expected_reaction {
+            LintRuleReaction::Error => {
+                handler.struct_span_err(span, MESSAGE).emit();
+            }
+            LintRuleReaction::Warning => {
+                handler.struct_span_warn(span, MESSAGE).emit();
+            }
+            _ => {}
+        });
+    }
+
+    fn check_case(&self, cases_count: usize, pos: usize, case: &SwitchCase) {
+        if case.test.is_none() && pos != cases_count {
+            self.emit_report(case.span);
+        }
+    }
+}
+
+impl Visit for DefaultCaseLast {
+    fn visit_switch_stmt(&mut self, switch_stmt: &SwitchStmt) {
+        let cases_count = switch_stmt.cases.len();
+
+        switch_stmt.discriminant.visit_children_with(self);
+
+        switch_stmt
+            .cases
+            .iter()
+            .enumerate()
+            .for_each(|(idx, switch_case)| {
+                self.check_case(cases_count, idx + 1, switch_case);
+
+                switch_case.visit_children_with(self);
+            });
+    }
+}

crates/swc_ecma_lints/src/rules/mod.rs

@@ -15,6 +15,7 @@ mod utils;
 #[cfg(feature = "non_critical_lints")]
 #[path = ""]
 pub(crate) mod non_critical_lints {
+    pub mod default_case_last;
     pub mod default_param_last;
     pub mod dot_notation;
     pub mod eqeqeq;
@@ -176,6 +177,10 @@ pub fn all(lint_params: LintParams) -> Vec<Box<dyn Rule>> {
         rules.extend(no_sparse_arrays::no_sparse_arrays(
             &lint_config.no_sparse_arrays,
         ));
+
+        rules.extend(default_case_last::default_case_last(
+            &lint_config.default_case_last,
+        ));
     }
 
     rules