[Installer] Fix for empty app-extension targets

Installation of app-extension targets which had no dependencies
configured in the Podfile would cause an exception before.

CHANGELOG.md

@@ -13,6 +13,13 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
   [Kyle Fuller](https://github.com/kylef)
   [#2996](https://github.com/CocoaPods/CocoaPods/issues/2996)
 
+##### Bug Fixes
+
+* Fixed installation for app-extension targets which had no dependencies
+  configured in the Podfile.  
+  [Boris Bügling](https://github.com/neonichu)
+  [#3102](https://github.com/CocoaPods/CocoaPods/issues/3102)
+
 
 ## 0.36.0.beta.2
 

lib/cocoapods/installer.rb

@@ -468,9 +468,10 @@ module Pod
       frameworks_group = pods_project.frameworks_group
       aggregate_targets.each do |aggregate_target|
         is_app_extension = aggregate_target.user_targets.map(&:symbol_type).include?(:app_extension)
-        configure_app_extension_api_only_for_target(aggregate_target) if is_app_extension
 
         aggregate_target.pod_targets.each do |pod_target|
+          configure_app_extension_api_only_for_target(aggregate_target) if is_app_extension
+
           unless pod_target.should_build?
             pod_target.resource_bundle_targets.each do |resource_bundle_target|
               aggregate_target.native_target.add_dependency(resource_bundle_target)

spec/unit/installer_spec.rb

@@ -456,6 +456,18 @@ module Pod
           build_settings.should == { 'APPLICATION_EXTENSION_API_ONLY' => 'YES' }
         end
 
+        it 'does not try to set APPLICATION_EXTENSION_API_ONLY if there are no pod targets' do
+          lambda do
+            mock_user_target = mock('UserTarget', :symbol_type => :app_extension)
+            @target.stubs(:user_targets).returns([mock_user_target])
+
+            @target.stubs(:native_target).returns(nil)
+            @target.stubs(:pod_targets).returns([])
+
+            @installer.send(:set_target_dependencies)
+          end.should.not.raise NoMethodError
+        end
+
         xit 'sets the pod targets as dependencies of the aggregate target' do
         end