Fix: extends chain (fixes #5411)

- I added a parameter `relativeTo` to `load` and `applyExtends`, then
set the directory of the config file to the parameter.

lib/config/config-file.js

@@ -304,7 +304,6 @@ function write(config, filePath) {
  * @private
  */
 function getLookupPath(configFilePath) {
-
     // calculates the path of the project including ESLint as dependency
     var projectPath = path.resolve(__dirname, "../../../");
     if (configFilePath && pathIsInside(configFilePath, projectPath)) {
@@ -322,11 +321,12 @@ function getLookupPath(configFilePath) {
  * @param {Object} config The configuration information.
  * @param {string} filePath The file path from which the configuration information
  *      was loaded.
+ * @param {string} [relativeTo] The path to resolve relative to.
  * @returns {Object} A new configuration object with all of the "extends" fields
  *      loaded and merged.
  * @private
  */
-function applyExtends(config, filePath) {
+function applyExtends(config, filePath, relativeTo) {
     var configExtends = config.extends;
 
     // normalize into an array for easier handling
@@ -352,7 +352,7 @@ function applyExtends(config, filePath) {
 
         try {
             debug("Loading " + parentPath);
-            return ConfigOps.merge(load(parentPath), previousValue);
+            return ConfigOps.merge(load(parentPath, false, relativeTo), previousValue);
         } catch (e) {
             // If the file referenced by `extends` failed to load, add the path to the
             // configuration file that referenced it to the error message so the user is
@@ -402,7 +402,6 @@ function normalizePackageName(name, prefix) {
  * @private
  */
 function resolve(filePath, relativeTo) {
-
     if (isFilePath(filePath)) {
         return { filePath: path.resolve(relativeTo || "", filePath) };
     } else {
@@ -428,12 +427,13 @@ function resolve(filePath, relativeTo) {
  * @param {string} filePath The filename or package name to load the configuration
  *      information from.
  * @param {boolean} [applyEnvironments=false] Set to true to merge in environment settings.
+ * @param {string} [relativeTo] The path to resolve relative to.
  * @returns {Object} The configuration information.
  * @private
  */
-function load(filePath, applyEnvironments) {
-
-    var resolvedPath = resolve(filePath),
+function load(filePath, applyEnvironments, relativeTo) {
+    var resolvedPath = resolve(filePath, relativeTo),
+        basedir = getLookupPath(path.dirname(resolvedPath.filePath)),
         config = loadConfigFile(resolvedPath);
 
     if (config) {
@@ -450,9 +450,7 @@ function load(filePath, applyEnvironments) {
 
         // include full path of parser if present
         if (config.parser) {
-            config.parser = resolveModule.sync(config.parser, {
-                basedir: getLookupPath(path.dirname(path.resolve(filePath)))
-            });
+            config.parser = resolveModule.sync(config.parser, {basedir: basedir});
         }
 
         // validate the configuration before continuing
@@ -461,7 +459,7 @@ function load(filePath, applyEnvironments) {
         // If an `extends` property is defined, it represents a configuration file to use as
         // a "parent". Load the referenced file and merge the configuration recursively.
         if (config.extends) {
-            config = applyExtends(config, filePath);
+            config = applyExtends(config, filePath, basedir);
         }
 
         if (config.env && applyEnvironments) {

tests/fixtures/config-extends/resolving-relatively/.eslintrc.json

@@ -0,0 +1,3 @@
+{
+    "extends": "a"
+}

tests/fixtures/config-file/extends-chain/.eslintrc.json

@@ -0,0 +1,3 @@
+{
+    "extends": "a"
+}

tests/lib/config/config-file.js

@@ -608,6 +608,20 @@ describe("ConfigFile", function() {
             });
         });
 
+        it("should load information from `extends` chain.", function() {
+            var config = ConfigFile.load(getFixturePath("extends-chain/.eslintrc.json"));
+            assert.deepEqual(config, {
+                env: {},
+                extends: "a",
+                globals: {},
+                parserOptions: {},
+                rules: {
+                    a: 2, // from node_modules/eslint-config-a
+                    b: 2, // from node_modules/eslint-config-a/node_modules/eslint-config-b
+                    c: 2  // from node_modules/eslint-config-a/node_modules/eslint-config-b/node_modules/eslint-config-c
+                }
+            });
+        });
 
         describe("Plugins", function() {