Fix: Corrected notice for invalid (:) plugin names

lib/cli-engine/config-array-factory.js

@@ -274,14 +274,15 @@ function loadESLintIgnoreFile(filePath) {
  * Creates an error to notify about a missing config to extend from.
  * @param {string} configName The name of the missing config.
  * @param {string} importerName The name of the config that imported the missing config
+ * @param {string} messageTemplate The text tempalte to source error strings from.
  * @returns {Error} The error object to throw
  * @private
  */
-function configMissingError(configName, importerName) {
+function configInvalidError(configName, importerName, messageTemplate) {
     return Object.assign(
         new Error(`Failed to load config "${configName}" to extend from.`),
         {
-            messageTemplate: "extend-config-missing",
+            messageTemplate,
             messageData: { configName, importerName }
         }
     );
@@ -790,7 +791,7 @@ class ConfigArrayFactory {
             });
         }
 
-        throw configMissingError(extendName, ctx.name);
+        throw configInvalidError(extendName, ctx.name, "extend-config-missing");
     }
 
     /**
@@ -802,6 +803,11 @@ class ConfigArrayFactory {
      */
     _loadExtendedPluginConfig(extendName, ctx) {
         const slashIndex = extendName.lastIndexOf("/");
+
+        if (slashIndex === -1) {
+            throw configInvalidError(extendName, ctx.filePath, "plugin-invalid");
+        }
+
         const pluginName = extendName.slice("plugin:".length, slashIndex);
         const configName = extendName.slice(slashIndex + 1);
 
@@ -822,7 +828,7 @@ class ConfigArrayFactory {
             });
         }
 
-        throw plugin.error || configMissingError(extendName, ctx.filePath);
+        throw plugin.error || configInvalidError(extendName, ctx.filePath, "extend-config-missing");
     }
 
     /**
@@ -855,7 +861,7 @@ class ConfigArrayFactory {
         } catch (error) {
             /* istanbul ignore else */
             if (error && error.code === "MODULE_NOT_FOUND") {
-                throw configMissingError(extendName, ctx.filePath);
+                throw configInvalidError(extendName, ctx.filePath, "extend-config-missing");
             }
             throw error;
         }

lib/shared/naming.js

@@ -43,7 +43,7 @@ function normalizePackageName(name, prefix) {
              */
             normalizedName = normalizedName.replace(/^@([^/]+)\/(.*)$/u, `@$1/${prefix}-$2`);
         }
-    } else if (!normalizedName.startsWith(`${prefix}-`)) {
+    } else if (!normalizedName.startsWith(`${prefix}-`) && normalizedName.indexOf(":") === -1) {
         normalizedName = `${prefix}-${normalizedName}`;
     }
 

messages/plugin-invalid.txt

@@ -0,0 +1,9 @@
+ESLint couldn't find the plugin "<%- pluginName %>".
+
+(The package "<%- pluginName %>" was not found when loaded as a Node module from the directory "<%- resolvePluginsRelativeTo %>".)
+
+It looks like this might not be a valid plugin name. Did you use the name of a shareable config instead of a plugin?
+
+The plugin "<%- pluginName %>" was referenced from the config file in "<%- importerName %>".
+
+If you still can't figure out the problem, please stop by https://eslint.org/chat/help to chat with the team.

tests/lib/cli-engine/config-array-factory.js

@@ -1503,6 +1503,23 @@ describe("ConfigArrayFactory", () => {
             }, /Failed to load config "plugin:invalid-config\/bar" to extend from./u);
         });
 
+        it("should throw an error with a message template when a plugin referenced for a plugin config is invalid", () => {
+            try {
+                applyExtends({
+                    extends: "plugin:nonexistent-plugin",
+                    rules: { eqeqeq: 2 }
+                });
+            } catch (err) {
+                assert.strictEqual(err.messageTemplate, "plugin-invalid");
+                assert.deepStrictEqual(err.messageData, {
+                    configName: "plugin:nonexistent-plugin",
+                    importerName: path.join(process.cwd(), "whatever")
+                });
+                return;
+            }
+            assert.fail("Expected to throw an error");
+        });
+
         it("should throw an error with a message template when a plugin referenced for a plugin config is not found", () => {
             try {
                 applyExtends({

tests/lib/shared/naming.js

@@ -25,7 +25,8 @@ describe("naming", () => {
             ["@z\\foo", "@z/eslint-config-foo"],
             ["@z\\foo\\bar.js", "@z/eslint-config-foo/bar.js"],
             ["@z/eslint-config", "@z/eslint-config"],
-            ["@z/eslint-config-foo", "@z/eslint-config-foo"]
+            ["@z/eslint-config-foo", "@z/eslint-config-foo"],
+            ["plugin:invalid", "plugin:invalid"]
         ], (input, expected) => {
             it(`should return ${expected} when passed ${input}`, () => {
                 const result = naming.normalizePackageName(input, "eslint-config");