[Integration] Fix integration while project is open

While a user project is open and we delete/change the xcconfig files which
the user project references. It causes any subsequent builds to fail
until the project is closed/re-opened, or the project file is touched.

This commit touches the file if we do not need to save it, thus causing
Xcode to reload it.

Closes #2627
Closes #2665

CHANGELOG.md

@@ -21,6 +21,13 @@ To install or update CocoaPods see this [guide](http://docs.cocoapods.org/guides
   [Samuel Giddins](https://github.com/segiddins)
   [#2494](https://github.com/CocoaPods/CocoaPods/issues/2494)
 
+* Fixes an issue where running `pod install/update` while the Xcode project
+  is open can cause the open project to have build failures until Xcode
+  is restarted.  
+  [Kyle Fuller](https://github.com/kylef)
+  [#2627](https://github.com/CocoaPods/CocoaPods/issues/2627)
+  [#2665](https://github.com/CocoaPods/CocoaPods/issues/2665)
+
 
 ## 0.34.2
 

lib/cocoapods/installer/user_project_integrator/target_integrator.rb

@@ -27,14 +27,30 @@ module Pod
         #
         def integrate!
           UI.section(integration_message) do
-            user_project.save if XCConfigIntegrator.integrate(target, native_targets)
-            user_project.save if update_to_cocoapods_0_34
+            # TODO: refactor into Xcodeproj https://github.com/CocoaPods/Xcodeproj/issues/202
+            project_is_dirty = [
+              XCConfigIntegrator.integrate(target, native_targets),
+              update_to_cocoapods_0_34,
+              unless native_targets_to_integrate.empty?
+                add_pods_library
+                add_copy_resources_script_phase
+                add_check_manifest_lock_script_phase
+                true
+              end
+            ].any?
 
-            unless native_targets_to_integrate.empty?
-              add_pods_library
-              add_copy_resources_script_phase
-              add_check_manifest_lock_script_phase
+            if project_is_dirty
               user_project.save
+            else
+              # There is a bug in Xcode where the process of deleting and
+              # re-creating the xcconfig files used in the build
+              # configuration cause building the user project to fail until
+              # Xcode is relaunched.
+              #
+              # Touching/saving the project causes Xcode to reload these.
+              #
+              # https://github.com/CocoaPods/CocoaPods/issues/2665
+              FileUtils.touch(user_project.path + 'project.pbxproj')
             end
           end
         end