Protect against circular extended configurations

lib/apply-extends.js

@@ -1,12 +1,25 @@
 var fs = require('fs')
 var path = require('path')
 var assign = require('./assign')
+var YError = require('./yerror')
+
+var previouslyVisitedConfigs = []
+
+function checkForCircularExtends (path) {
+  if (previouslyVisitedConfigs.indexOf(path) > -1) {
+    throw new YError("Circular extended configurations: '" + path + "'.")
+  }
+}
 
 function applyExtends (config, cwd, subKey) {
   var defaultConfig = {}
 
   if (config.hasOwnProperty('extends')) {
     var pathToDefault = path.join(cwd, config.extends)
+
+    checkForCircularExtends(pathToDefault)
+
+    previouslyVisitedConfigs.push(pathToDefault)
     delete config.extends
 
     defaultConfig = JSON.parse(fs.readFileSync(pathToDefault, 'utf8'))
@@ -16,6 +29,8 @@ function applyExtends (config, cwd, subKey) {
     defaultConfig = applyExtends(defaultConfig, path.dirname(pathToDefault), subKey)
   }
 
+  previouslyVisitedConfigs = []
+
   return assign(defaultConfig, config)
 }
 

test/fixtures/extends/circular_1.json

@@ -0,0 +1,4 @@
+{
+  "a": 44,
+  "extends": "./circular_2.json"
+}

test/fixtures/extends/circular_2.json

@@ -0,0 +1,4 @@
+{
+  "b": "any",
+  "extends": "./circular_1.json"
+}

test/yargs.js

@@ -5,6 +5,7 @@ var fs = require('fs')
 var path = require('path')
 var checkOutput = require('./helpers/utils').checkOutput
 var yargs = require('../')
+var YError = require('../lib/yerror')
 
 require('chai').should()
 
@@ -1169,6 +1170,12 @@ describe('yargs dsl tests', function () {
         argv.b.should.equal(22)
         argv.z.should.equal(15)
       })
+
+      it('protects against circular extended configurations', function () {
+        expect(function () {
+          yargs.config({extends: './test/fixtures/extends/circular_1.json'})
+        }).to.throw(YError)
+      })
     })
   })