no-duplicate-branches: Fix switch/case reporting (#114)

Author: andrea-guarino-sonarsource

src/rules/no-duplicated-branches.ts

@@ -72,21 +72,20 @@ const rule: Rule.RuleModule = {
     function visitSwitchStatement(switchStmt: estree.SwitchStatement) {
       const { cases } = switchStmt;
       const { endsWithDefault } = collectSwitchBranches(switchStmt);
-      const nonEmptyCases = cases
-        .map(c => takeWithoutBreak(expandSingleBlockStatement(c.consequent)))
-        .filter(c => c.length > 0);
+      const nonEmptyCases = cases.filter(c => takeWithoutBreak(expandSingleBlockStatement(c.consequent)).length > 0);
+      const casesWithoutBreak = nonEmptyCases.map(c => takeWithoutBreak(expandSingleBlockStatement(c.consequent)));
 
-      if (allEquivalentWithoutDefault(nonEmptyCases, endsWithDefault)) {
-        cases.slice(1).forEach((caseStmt, i) => reportIssue(caseStmt, cases[i], "case"));
+      if (allEquivalentWithoutDefault(casesWithoutBreak, endsWithDefault)) {
+        nonEmptyCases.slice(1).forEach((caseStmt, i) => reportIssue(caseStmt, nonEmptyCases[i], "case"));
         return;
       }
 
-      for (let i = 1; i < nonEmptyCases.length; i++) {
-        const firstClauseWithoutBreak = nonEmptyCases[i];
+      for (let i = 1; i < cases.length; i++) {
+        const firstClauseWithoutBreak = takeWithoutBreak(expandSingleBlockStatement(cases[i].consequent));
 
         if (hasRequiredSize(firstClauseWithoutBreak)) {
           for (let j = 0; j < i; j++) {
-            const secondClauseWithoutBreak = nonEmptyCases[j];
+            const secondClauseWithoutBreak = takeWithoutBreak(expandSingleBlockStatement(cases[j].consequent));
 
             if (areEquivalent(firstClauseWithoutBreak, secondClauseWithoutBreak, context.getSourceCode())) {
               reportIssue(cases[i], cases[j], "case");

tests/rules/no-duplicated-branches.test.ts

@@ -233,6 +233,21 @@ ruleTester.run("no-duplicated-branches switch", rule, {
     },
   ],
   invalid: [
+    {
+      code: `
+      switch(a) {
+        case 2:
+        case 1:
+          first();
+          second();
+          break;
+        case 3:
+          first();
+          second();
+          break;
+      }`,
+      errors: [{ line: 8 }],
+    },
     {
       code: `
       switch (a) {
@@ -353,5 +368,24 @@ ruleTester.run("no-duplicated-branches switch", rule, {
       }`,
       errors: [{ line: 6, message: "This case's code block is the same as the block for the case on line 3." }],
     },
+    {
+      code: `
+      switch(a) {
+        case 0:
+          foo();
+          bar();
+          break;
+        case 2:
+        case 1:
+          first();
+          second();
+          break;
+        case 3:
+          first();
+          second();
+          break;
+      }`,
+      errors: [{ line: 12, message: "This case's code block is the same as the block for the case on line 8." }],
+    },
   ],
 });