From 31e79399d0ad2e94bd5ad832f994d46b2bb4fa1e Mon Sep 17 00:00:00 2001
From: Milos Djermanovic <milos.djermanovic@gmail.com>
Date: Tue, 19 Oct 2021 14:18:52 +0200
Subject: [PATCH] Fix: allow `baseConfig` to extend preloaded plugin config
 (fixes #15079)

---
 lib/cli-engine/cli-engine.js | 11 ++++++++++-
 lib/eslint/eslint.js         | 17 ++---------------
 tests/lib/eslint/eslint.js   | 30 ++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 16 deletions(-)

diff --git a/lib/cli-engine/cli-engine.js b/lib/cli-engine/cli-engine.js
index aae71607d2c..7fba116c771 100644
--- a/lib/cli-engine/cli-engine.js
+++ b/lib/cli-engine/cli-engine.js
@@ -570,8 +570,10 @@ class CLIEngine {
     /**
      * Creates a new instance of the core CLI engine.
      * @param {CLIEngineOptions} providedOptions The options for this instance.
+     * @param {Object} [additionalData] Additional settings that are not CLIEngineOptions.
+     * @param {Record<string,Plugin>|null} [additionalData.preloadedPlugins] Preloaded plugins.
      */
-    constructor(providedOptions) {
+    constructor(providedOptions, { preloadedPlugins } = {}) {
         const options = Object.assign(
             Object.create(null),
             defaultOptions,
@@ -584,6 +586,13 @@ class CLIEngine {
         }
 
         const additionalPluginPool = new Map();
+
+        if (preloadedPlugins) {
+            for (const [id, plugin] of Object.entries(preloadedPlugins)) {
+                additionalPluginPool.set(id, plugin);
+            }
+        }
+
         const cacheFilePath = getCacheFile(
             options.cacheLocation || options.cacheFile,
             options.cwd
diff --git a/lib/eslint/eslint.js b/lib/eslint/eslint.js
index b4a1d028db9..8886d45ab43 100644
--- a/lib/eslint/eslint.js
+++ b/lib/eslint/eslint.js
@@ -54,7 +54,7 @@ const { version } = require("../../package.json");
  * @property {string} [ignorePath] The ignore file to use instead of .eslintignore.
  * @property {ConfigData} [overrideConfig] Override config object, overrides all configs used with this instance
  * @property {string} [overrideConfigFile] The configuration file to use.
- * @property {Record<string,Plugin>} [plugins] An array of plugin implementations.
+ * @property {Record<string,Plugin>|null} [plugins] Preloaded plugins. This is a map-like object, keys are plugin IDs and each value is implementation.
  * @property {"error" | "warn" | "off"} [reportUnusedDisableDirectives] the severity to report unused eslint-disable directives.
  * @property {string} [resolvePluginsRelativeTo] The folder where plugins should be resolved from, defaulting to the CWD.
  * @property {string[]} [rulePaths] An array of directories to load custom rules from.
@@ -433,26 +433,13 @@ class ESLint {
      */
     constructor(options = {}) {
         const processedOptions = processOptions(options);
-        const cliEngine = new CLIEngine(processedOptions);
+        const cliEngine = new CLIEngine(processedOptions, { preloadedPlugins: options.plugins });
         const {
-            additionalPluginPool,
             configArrayFactory,
             lastConfigArrays
         } = getCLIEngineInternalSlots(cliEngine);
         let updated = false;
 
-        /*
-         * Address `plugins` to add plugin implementations.
-         * Operate the `additionalPluginPool` internal slot directly to avoid
-         * using `addPlugin(id, plugin)` method that resets cache everytime.
-         */
-        if (options.plugins) {
-            for (const [id, plugin] of Object.entries(options.plugins)) {
-                additionalPluginPool.set(id, plugin);
-                updated = true;
-            }
-        }
-
         /*
          * Address `overrideConfig` to set override config.
          * Operate the `configArrayFactory` internal slot directly because this
diff --git a/tests/lib/eslint/eslint.js b/tests/lib/eslint/eslint.js
index 1a51a65d841..eaf4aaaaf05 100644
--- a/tests/lib/eslint/eslint.js
+++ b/tests/lib/eslint/eslint.js
@@ -2095,6 +2095,36 @@ describe("ESLint", () => {
                 assert.strictEqual(results[0].messages[0].ruleId, "test/example-rule");
             });
 
+            it("should return two messages when executing with `baseConfig` that extends preloaded plugin config", async () => {
+                eslint = new ESLint({
+                    cwd: path.join(fixtureDir, ".."),
+                    useEslintrc: false,
+                    baseConfig: {
+                        extends: ["plugin:test/preset"]
+                    },
+                    plugins: {
+                        test: {
+                            rules: {
+                                "example-rule": require("../../fixtures/rules/custom-rule")
+                            },
+                            configs: {
+                                preset: {
+                                    rules: {
+                                        "test/example-rule": 1
+                                    },
+                                    plugins: ["test"]
+                                }
+                            }
+                        }
+                    }
+                });
+                const results = await eslint.lintFiles([fs.realpathSync(getFixturePath("rules", "test", "test-custom-rule.js"))]);
+
+                assert.strictEqual(results.length, 1);
+                assert.strictEqual(results[0].messages.length, 2);
+                assert.strictEqual(results[0].messages[0].ruleId, "test/example-rule");
+            });
+
             it("should load plugins from the `loadPluginsRelativeTo` directory, if specified", async () => {
                 eslint = new ESLint({
                     resolvePluginsRelativeTo: getFixturePath("plugins"),