From 597c217f2c0ac5ca4bd1ddad321f2192a88fc40f Mon Sep 17 00:00:00 2001
From: Calvin Freitas <calvin.freitas@gmail.com>
Date: Sun, 9 Jul 2017 11:20:23 -0700
Subject: [PATCH] Fix: confusing error if plugins from config is not an array
 (#8888)

---
 lib/config/plugins.js       | 12 ++++++++++++
 tests/lib/config/plugins.js |  4 ++++
 2 files changed, 16 insertions(+)

diff --git a/lib/config/plugins.js b/lib/config/plugins.js
index 11852df5c96..adfd8a1bbe3 100644
--- a/lib/config/plugins.js
+++ b/lib/config/plugins.js
@@ -156,8 +156,20 @@ class Plugins {
      * @param {string[]} pluginNames An array of plugins names.
      * @returns {void}
      * @throws {Error} If a plugin cannot be loaded.
+     * @throws {Error} If "plugins" in config is not an array
      */
     loadAll(pluginNames) {
+
+        // if "plugins" in config is not an array, throw an error so user can fix their config.
+        if (!Array.isArray(pluginNames)) {
+            const pluginNotArrayMessage = "ESLint configuration error: \"plugins\" value must be an array";
+
+            debug(`${pluginNotArrayMessage}: ${JSON.stringify(pluginNames)}`);
+
+            throw new Error(pluginNotArrayMessage);
+        }
+
+        // load each plugin by name
         pluginNames.forEach(this.load, this);
     }
 }
diff --git a/tests/lib/config/plugins.js b/tests/lib/config/plugins.js
index 00b53af7262..4b165ea4ead 100644
--- a/tests/lib/config/plugins.js
+++ b/tests/lib/config/plugins.js
@@ -236,6 +236,10 @@ describe("Plugins", () => {
             assert.equal(rules.get("example2/bar"), plugin2.rules.bar);
         });
 
+        it("should throw an error if plugins is not an array", () => {
+            assert.throws(() => StubbedPlugins.loadAll("example1"), "\"plugins\" value must be an array");
+        });
+
     });
 
     describe("removePrefix()", () => {