From ac606217d4beebc35b865d14a7f9723fd21faa48 Mon Sep 17 00:00:00 2001
From: YeonJuan <yeonjuan93@naver.com>
Date: Tue, 5 Nov 2019 03:15:57 +0900
Subject: [PATCH] Fix: unexpected autofix in prefer-const (fixes #12514)
 (#12521)

---
 lib/rules/prefer-const.js       | 21 ++++++++++++++-------
 tests/lib/rules/prefer-const.js | 19 +++++++++++++++++++
 2 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/lib/rules/prefer-const.js b/lib/rules/prefer-const.js
index 87f83892126..439a4db3c96 100644
--- a/lib/rules/prefer-const.js
+++ b/lib/rules/prefer-const.js
@@ -356,7 +356,9 @@ module.exports = {
         const ignoreReadBeforeAssign = options.ignoreReadBeforeAssign === true;
         const variables = [];
         let reportCount = 0;
-        let name = "";
+        let checkedId = null;
+        let checkedName = "";
+
 
         /**
          * Reports given identifier nodes if all of the nodes should be declared
@@ -387,25 +389,30 @@ module.exports = {
                         /*
                          * First we check the declaration type and then depending on
                          * if the type is a "VariableDeclarator" or its an "ObjectPattern"
-                         * we compare the name from the first identifier, if the names are different
-                         * we assign the new name and reset the count of reportCount and nodeCount in
+                         * we compare the name and id from the first identifier, if the names are different
+                         * we assign the new name, id and reset the count of reportCount and nodeCount in
                          * order to check each block for the number of reported errors and base our fix
                          * based on comparing nodes.length and nodesToReport.length.
                          */
 
                         if (firstDecParent.type === "VariableDeclarator") {
 
-                            if (firstDecParent.id.name !== name) {
-                                name = firstDecParent.id.name;
+                            if (firstDecParent.id.name !== checkedName) {
+                                checkedName = firstDecParent.id.name;
                                 reportCount = 0;
                             }
 
                             if (firstDecParent.id.type === "ObjectPattern") {
-                                if (firstDecParent.init.name !== name) {
-                                    name = firstDecParent.init.name;
+                                if (firstDecParent.init.name !== checkedName) {
+                                    checkedName = firstDecParent.init.name;
                                     reportCount = 0;
                                 }
                             }
+
+                            if (firstDecParent.id !== checkedId) {
+                                checkedId = firstDecParent.id;
+                                reportCount = 0;
+                            }
                         }
                     }
                 }
diff --git a/tests/lib/rules/prefer-const.js b/tests/lib/rules/prefer-const.js
index d923985337b..ad25f5f4830 100644
--- a/tests/lib/rules/prefer-const.js
+++ b/tests/lib/rules/prefer-const.js
@@ -527,6 +527,25 @@ ruleTester.run("prefer-const", rule, {
                 { messageId: "useConst", data: { name: "b" }, type: "Identifier" },
                 { messageId: "useConst", data: { name: "c" }, type: "Identifier" }
             ]
+        },
+        {
+            code: [
+                "function a() {",
+                "let foo = 0,",
+                "  bar = 1;",
+                "foo = 1;",
+                "}",
+                "function b() {",
+                "let foo = 0,",
+                "  bar = 2;",
+                "foo = 2;",
+                "}"
+            ].join("\n"),
+            output: null,
+            errors: [
+                { message: "'bar' is never reassigned. Use 'const' instead.", type: "Identifier" },
+                { message: "'bar' is never reassigned. Use 'const' instead.", type: "Identifier" }
+            ]
         }
     ]
 });