fix: Do not merge arrays or custom class instances

index.js

@@ -39,7 +39,17 @@ module.exports = class Conf {
   }
 
   merge (obj) {
-    return _.merge(this.config, obj)
+    return _.mergeWith(this.config, obj, (configValue, overrideValue) => {
+      // Do not apply merge on non-plain objects
+      if (typeof overrideValue === 'object' && overrideValue.constructor !== Object) {
+        return overrideValue
+      }
+
+      // Do not apply merge on arrays
+      if (Array.isArray(overrideValue)) {
+        return overrideValue
+      }
+    })
   }
 
   toString () {
@@ -61,11 +71,12 @@ function loadFile (parts, opts) {
 }
 
 function getEnvVariables () {
-  return _.reduce(process.env, function (obj, val, key) {
+  const env = {}
+  for (const key of Object.keys(process.env)) {
     const k = key.split('__').join('/')
-    pointer.set(obj, strToPointer(k), val)
-    return obj
-  }, {})
+    pointer.set(env, strToPointer(k), process.env[key])
+  }
+  return env
 }
 
 function strToPointer (str) {

test/unit/conf_tests.js

@@ -155,6 +155,27 @@ describe('The Conf', () => {
       expect(config.get('added')).to.be.true
     })
 
+    it('does not merge arrays', function () {
+      const config = new Conf({foo: ['foo', 'bar']})
+
+      config.merge({foo: ['quz']})
+      expect(config.get('foo')).to.deep.equal(['quz'])
+    })
+
+    it('does not merge class instances, keeps the original object', function () {
+      class Foo {
+        constructor () {
+          this.foo = 'foo'
+        }
+      }
+
+      const config = new Conf({foo: {bar: 'bar'}})
+
+      const foo = new Foo()
+      config.merge({foo})
+      expect(config.get('foo')).to.equal(foo)
+      expect(foo.bar).to.equal(undefined)
+    })
   })
 
   describe('set:', () => {