Fix: no-undef-init autofix removes comments

lib/rules/no-undef-init.js

@@ -37,7 +37,8 @@ module.exports = {
                     init = node.init && node.init.name,
                     scope = context.getScope(),
                     undefinedVar = astUtils.getVariableByName(scope, "undefined"),
-                    shadowed = undefinedVar && undefinedVar.defs.length > 0;
+                    shadowed = undefinedVar && undefinedVar.defs.length > 0,
+                    lastToken = sourceCode.getLastToken(node);
 
                 if (init === "undefined" && node.parent.kind !== "const" && !shadowed) {
                     context.report({
@@ -54,6 +55,11 @@ module.exports = {
                                 // Don't fix destructuring assignment to `undefined`.
                                 return null;
                             }
+
+                            if (sourceCode.commentsExistBetween(node.id, lastToken)) {
+                                return null;
+                            }
+
                             return fixer.removeRange([node.id.range[1], node.range[1]]);
                         }
                     });

tests/lib/rules/no-undef-init.js

@@ -92,6 +92,62 @@ ruleTester.run("no-undef-init", rule, {
             output: "for(var i in [1,2,3]){let a; for(var j in [1,2,3]){}}",
             parserOptions: { ecmaVersion: 6 },
             errors: [{ message: "It's not necessary to initialize 'a' to undefined.", type: "VariableDeclarator" }]
+        },
+
+        // Should not autofix if it would remove comments
+        {
+            code: "let /* comment */a = undefined;",
+            output: "let /* comment */a;",
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ message: "It's not necessary to initialize 'a' to undefined.", type: "VariableDeclarator" }]
+        },
+        {
+            code: "let a/**/ = undefined;",
+            output: null,
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ message: "It's not necessary to initialize 'a' to undefined.", type: "VariableDeclarator" }]
+        },
+        {
+            code: "let a /**/ = undefined;",
+            output: null,
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ message: "It's not necessary to initialize 'a' to undefined.", type: "VariableDeclarator" }]
+        },
+        {
+            code: "let a//\n= undefined;",
+            output: null,
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ message: "It's not necessary to initialize 'a' to undefined.", type: "VariableDeclarator" }]
+        },
+        {
+            code: "let a = /**/undefined;",
+            output: null,
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ message: "It's not necessary to initialize 'a' to undefined.", type: "VariableDeclarator" }]
+        },
+        {
+            code: "let a = //\nundefined;",
+            output: null,
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ message: "It's not necessary to initialize 'a' to undefined.", type: "VariableDeclarator" }]
+        },
+        {
+            code: "let a = undefined/* comment */;",
+            output: "let a/* comment */;",
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ message: "It's not necessary to initialize 'a' to undefined.", type: "VariableDeclarator" }]
+        },
+        {
+            code: "let a = undefined/* comment */, b;",
+            output: "let a/* comment */, b;",
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ message: "It's not necessary to initialize 'a' to undefined.", type: "VariableDeclarator" }]
+        },
+        {
+            code: "let a = undefined//comment\n, b;",
+            output: "let a//comment\n, b;",
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ message: "It's not necessary to initialize 'a' to undefined.", type: "VariableDeclarator" }]
         }
     ]
 });