From 4c87f428bc501e087ab4882dae9b4fd2bc22041d Mon Sep 17 00:00:00 2001
From: akouryy <akouryy@users.noreply.github.com>
Date: Sat, 30 Dec 2017 17:49:01 +0900
Subject: [PATCH] Fix: incorrect error messages of no-unused-vars (fixes #9774)
 (#9791)

Remove varsIgnorePattern incorrectly included in error messages of no-unused-vars.
---
 lib/rules/no-unused-vars.js       | 21 ++++++++-------------
 tests/lib/rules/no-unused-vars.js | 12 ++++++++++++
 2 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/lib/rules/no-unused-vars.js b/lib/rules/no-unused-vars.js
index 05940d5932a..04c2bc87996 100644
--- a/lib/rules/no-unused-vars.js
+++ b/lib/rules/no-unused-vars.js
@@ -105,26 +105,21 @@ module.exports = {
          * @returns {string} The warning message to be used with this unused variable.
          */
         function getDefinedMessage(unusedVar) {
+            const defType = unusedVar.defs && unusedVar.defs[0] && unusedVar.defs[0].type;
             let type;
             let pattern;
 
-            if (config.varsIgnorePattern) {
+            if (defType === "CatchClause" && config.caughtErrorsIgnorePattern) {
+                type = "args";
+                pattern = config.caughtErrorsIgnorePattern.toString();
+            } else if (defType === "Parameter" && config.argsIgnorePattern) {
+                type = "args";
+                pattern = config.argsIgnorePattern.toString();
+            } else if (defType !== "Parameter" && config.varsIgnorePattern) {
                 type = "vars";
                 pattern = config.varsIgnorePattern.toString();
             }
 
-            if (unusedVar.defs && unusedVar.defs[0] && unusedVar.defs[0].type) {
-                const defType = unusedVar.defs[0].type;
-
-                if (defType === "CatchClause" && config.caughtErrorsIgnorePattern) {
-                    type = "args";
-                    pattern = config.caughtErrorsIgnorePattern.toString();
-                } else if (defType === "Parameter" && config.argsIgnorePattern) {
-                    type = "args";
-                    pattern = config.argsIgnorePattern.toString();
-                }
-            }
-
             const additional = type ? ` Allowed unused ${type} must match ${pattern}.` : "";
 
             return `'{{name}}' is defined but never used.${additional}`;
diff --git a/tests/lib/rules/no-unused-vars.js b/tests/lib/rules/no-unused-vars.js
index 3e452ce3d66..9615c62dd8a 100644
--- a/tests/lib/rules/no-unused-vars.js
+++ b/tests/lib/rules/no-unused-vars.js
@@ -675,6 +675,18 @@ ruleTester.run("no-unused-vars", rule, {
                 "'a' is defined but never used.",
                 "'c' is defined but never used."
             ]
+        },
+
+        // https://github.com/eslint/eslint/issues/9774
+        {
+            code: "(function(_a) {})();",
+            options: [{ args: "all", varsIgnorePattern: "^_" }],
+            errors: [{ message: "'_a' is defined but never used." }]
+        },
+        {
+            code: "(function(_a) {})();",
+            options: [{ args: "all", caughtErrorsIgnorePattern: "^_" }],
+            errors: [{ message: "'_a' is defined but never used." }]
         }
     ]
 });