Merge pull request #5813 from eslint/issue4799

Fix: `no-fallthrough` empty case with comment (fixes #5799)
eslint · Apr 13, 2016 · 36d2f9a · 36d2f9a
2 parents 16787e1 + cc14e43
commit 36d2f9a
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Showing 2 changed files with 24 additions and 3 deletions.
diff --git a/lib/rules/no-fallthrough.js b/lib/rules/no-fallthrough.js
@@ -39,13 +39,24 @@ function isReachable(segment) {
     return segment.reachable;
 }
 
+/**
+ * Checks whether a node and a token are separated by blank lines
+ * @param {ASTNode} node - The node to check
+ * @param {Token} token - The token to compare against
+ * @returns {boolean} `true` if there are blank lines between node and token
+ */
+function hasBlankLinesBetween(node, token) {
+    return token.loc.start.line > node.loc.end.line + 1;
+}
+
 //------------------------------------------------------------------------------
 // Rule Definition
 //------------------------------------------------------------------------------
 
 module.exports = function(context) {
     var options = context.options[0] || {};
     var currentCodePath = null;
+    var sourceCode = context.getSourceCode();
 
     /*
      * We need to use leading comments of the next SwitchCase node because
@@ -85,16 +96,16 @@ module.exports = function(context) {
         },
 
         "SwitchCase:exit": function(node) {
+            var nextToken = sourceCode.getTokenAfter(node);
 
             /*
              * `reachable` meant fall through because statements preceded by
              * `break`, `return`, or `throw` are unreachable.
              * And allows empty cases and the last case.
              */
             if (currentCodePath.currentSegments.some(isReachable) &&
-                node.consequent.length > 0 &&
-                lodash.last(node.parent.cases) !== node
-            ) {
+                (node.consequent.length > 0 || hasBlankLinesBetween(node, nextToken)) &&
+                lodash.last(node.parent.cases) !== node) {
                 fallthroughCase = node;
             }
         }

diff --git a/tests/lib/rules/no-fallthrough.js b/tests/lib/rules/no-fallthrough.js
@@ -41,6 +41,8 @@ ruleTester.run("no-fallthrough", rule, {
         "switch(foo) { case 0: case 1: a(); }",
         "switch(foo) { case 0: case 1: a(); break; }",
         "switch(foo) { case 0: case 1: break; }",
+        "switch(foo) { case 0:\n case 1: break; }",
+        "switch(foo) { case 0: // comment\n case 1: break; }",
         "function foo() { switch(foo) { case 0: case 1: return; } }",
         "function foo() { switch(foo) { case 0: {return;}\n case 1: {return;} } }",
         "switch(foo) { case 0: case 1: {break;} }",
@@ -128,6 +130,14 @@ ruleTester.run("no-fallthrough", rule, {
             code: "switch(foo) { case 0: do { break; } while (a); default: b() }",
             errors: errorsDefault
         },
+        {
+            code: "switch(foo) { case 0:\n\n default: b() }",
+            errors: errorsDefault
+        },
+        {
+            code: "switch(foo) { case 0:\n // comment\n default: b() }",
+            errors: errorsDefault
+        },
         {
             code: "switch(foo) { case 0: a(); /* falling through */ default: b() }",
             errors: errorsDefault