Fix: extend prefer-const fixer range to whole declaration (fixes #13899…

…) (#14033) * Fix: extend fixer range of prefer const to whole declaration * Chore: update prefer-const test case
eslint · Jan 30, 2021 · fb27422 · fb27422
1 parent e0b05c7
commit fb27422
Show file tree

Hide file tree

Showing 2 changed files with 27 additions and 5 deletions.
diff --git a/lib/rules/prefer-const.js b/lib/rules/prefer-const.js
@@ -5,6 +5,11 @@
 
 "use strict";
 
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const FixTracker = require("./utils/fix-tracker");
 const astUtils = require("./utils/ast-utils");
 
 //------------------------------------------------------------------------------
@@ -451,10 +456,18 @@ module.exports = {
                         messageId: "useConst",
                         data: node,
                         fix: shouldFix
-                            ? fixer => fixer.replaceText(
-                                sourceCode.getFirstToken(varDeclParent, t => t.value === varDeclParent.kind),
-                                "const"
-                            )
+                            ? fixer => {
+                                const letKeywordToken = sourceCode.getFirstToken(varDeclParent, t => t.value === varDeclParent.kind);
+
+                                /**
+                                 * Extend the replacement range to the whole declaration,
+                                 * in order to prevent other fixes in the same pass
+                                 * https://github.com/eslint/eslint/issues/13899
+                                 */
+                                return new FixTracker(fixer, sourceCode)
+                                    .retainRange(varDeclParent.range)
+                                    .replaceTextRange(letKeywordToken.range, "const");
+                            }
                             : null
                     });
                 });

diff --git a/tests/lib/rules/prefer-const.js b/tests/lib/rules/prefer-const.js
@@ -500,9 +500,11 @@ ruleTester.run("prefer-const", rule, {
                 { message: "'b' is never reassigned. Use 'const' instead.", type: "Identifier" }
             ]
         },
+
+        // The inner `let` will be auto-fixed in the second pass
         {
             code: "let someFunc = () => { let a = 1, b = 2; foo(a, b) }",
-            output: "const someFunc = () => { const a = 1, b = 2; foo(a, b) }",
+            output: "const someFunc = () => { let a = 1, b = 2; foo(a, b) }",
             errors: [
                 { message: "'someFunc' is never reassigned. Use 'const' instead.", type: "Identifier" },
                 { message: "'a' is never reassigned. Use 'const' instead.", type: "Identifier" },
@@ -546,6 +548,13 @@ ruleTester.run("prefer-const", rule, {
                 { message: "'bar' is never reassigned. Use 'const' instead.", type: "Identifier" },
                 { message: "'bar' is never reassigned. Use 'const' instead.", type: "Identifier" }
             ]
+        },
+
+        // https://github.com/eslint/eslint/issues/13899
+        {
+            code: "/*eslint no-undef-init:error*/ let foo = undefined;",
+            output: "/*eslint no-undef-init:error*/ const foo = undefined;",
+            errors: 2
         }
     ]
 });