Fix additional empty line switch case comment (#936)

* Refactor condition in printStatementSequence, add new helper function.

* Add new test cases.

* Move logic in SwitchCase case.

* Revert unrelated changes, remove unecessary variables.

* Use util.getLast helper function.

* Move variables out of the loop.

* Simplify code.

* Fix mapping with mutated path.

src/printer.js

@@ -1173,13 +1173,15 @@ function genericPrintNoParens(path, options, print) {
       else parts.push("default:");
 
       if (n.consequent.find(node => node.type !== "EmptyStatement")) {
-        const cons = path.call(
-          function(consequentPath) {
-            return printStatementSequence(consequentPath, options, print);
-          },
-          "consequent"
-        );
-
+        const parent = path.getParentNode();
+        const lastCase = util.getLast(parent.cases);
+        const cons = path.call(consequentPath => {
+          return join(hardline, consequentPath.map(p => {
+            const shouldAddLine = p.getParentNode() !== lastCase &&
+              util.isNextLineEmpty(options.originalText, p.getValue());
+            return concat([print(p), shouldAddLine ? hardline : ""]);
+          }));
+        }, "consequent");
         parts.push(
           isCurlyBracket(cons)
             ? concat([" ", cons])

tests/comments/__snapshots__/jsfmt.spec.js.snap

@@ -1886,6 +1886,92 @@ function inlineComment() {
 "
 `;
 
+exports[`switch.js 1`] = `
+"switch (node && node.type) {
+  case \\"Property\\":
+  case \\"MethodDefinition\\":
+    prop = node.key;
+    break;
+
+  case \\"MemberExpression\\":
+    prop = node.property;
+    break;
+
+  // no default
+}
+
+switch (foo) {
+  case \\"bar\\":
+    doThing()
+
+  // no default
+}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+switch (node && node.type) {
+  case \\"Property\\":
+  case \\"MethodDefinition\\":
+    prop = node.key;
+    break;
+
+  case \\"MemberExpression\\":
+    prop = node.property;
+    break;
+
+  // no default
+}
+
+switch (foo) {
+  case \\"bar\\":
+    doThing();
+
+  // no default
+}
+"
+`;
+
+exports[`switch.js 2`] = `
+"switch (node && node.type) {
+  case \\"Property\\":
+  case \\"MethodDefinition\\":
+    prop = node.key;
+    break;
+
+  case \\"MemberExpression\\":
+    prop = node.property;
+    break;
+
+  // no default
+}
+
+switch (foo) {
+  case \\"bar\\":
+    doThing()
+
+  // no default
+}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+switch (node && node.type) {
+  case \\"Property\\":
+  case \\"MethodDefinition\\":
+    prop = node.key;
+    break;
+
+  case \\"MemberExpression\\":
+    prop = node.property;
+    break;
+
+  // no default
+}
+
+switch (foo) {
+  case \\"bar\\":
+    doThing();
+
+  // no default
+}
+"
+`;
+
 exports[`template-literal.js 1`] = `
 "\`
 \${a // comment

tests/comments/switch.js

@@ -0,0 +1,19 @@
+switch (node && node.type) {
+  case "Property":
+  case "MethodDefinition":
+    prop = node.key;
+    break;
+
+  case "MemberExpression":
+    prop = node.property;
+    break;
+
+  // no default
+}
+
+switch (foo) {
+  case "bar":
+    doThing()
+
+  // no default
+}