feat(typescript-estree): disallow switch statements with multiple def…

…ault cases (#8411)
typescript-eslint · Mar 16, 2024 · 994812b · 994812b
1 parent 093225c
commit 994812b
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diff --git a/...ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/fixture.ts b/...ast-spec/src/statement/SwitchStatement/fixtures/_error_/multiple-default-cases/fixture.ts
@@ -0,0 +1,3 @@
+switch (true) {
+	default: default:
+}
diff --git a/...t/SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/1-TSESTree-Error.shot b/...t/SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/1-TSESTree-Error.shot
diff --git a/...ment/SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/2-Babel-Error.shot b/...ment/SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/2-Babel-Error.shot
diff --git a/.../SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/3-Alignment-Error.shot b/.../SwitchStatement/fixtures/_error_/multiple-default-cases/snapshots/3-Alignment-Error.shot
diff --git a/packages/typescript-estree/src/convert.ts b/packages/typescript-estree/src/convert.ts
@@ -839,6 +839,17 @@ export class Converter {
         });
 
       case SyntaxKind.SwitchStatement:
+        if (
+          node.caseBlock.clauses.filter(
+            switchCase => switchCase.kind === SyntaxKind.DefaultClause,
+          ).length > 1
+        ) {
+          this.#throwError(
+            node,
+            "A 'default' clause cannot appear more than once in a 'switch' statement.",
+          );
+        }
+
         return this.createNode<TSESTree.SwitchStatement>(node, {
           type: AST_NODE_TYPES.SwitchStatement,
           discriminant: this.convertChild(node.expression),