[Installer] Fully deintegrate on major version change

lib/cocoapods.rb

@@ -40,6 +40,7 @@ module Pod
 
   autoload :AggregateTarget,           'cocoapods/target/aggregate_target'
   autoload :Command,                   'cocoapods/command'
+  autoload :Deintegrator,              'cocoapods_deintegrate'
   autoload :Executable,                'cocoapods/executable'
   autoload :ExternalSources,           'cocoapods/external_sources'
   autoload :Installer,                 'cocoapods/installer'

lib/cocoapods/installer.rb

@@ -121,6 +121,7 @@ module Pod
         raise Informative, message
       end
       UI.message 'Preparing' do
+        deintegrate_if_different_major_version
         sandbox.prepare
         ensure_plugins_are_installed!
         Migrator.migrate(sandbox)
@@ -486,6 +487,25 @@ module Pod
       context.sources
     end
 
+    # Run the deintegrator against all projects in the installation root if the
+    # current CocoaPods major version part is different than the one in the
+    # lockfile.
+    #
+    # @return [void]
+    #
+    def deintegrate_if_different_major_version
+      return unless config.lockfile
+      return if config.lockfile.cocoapods_version.major == Version.new(VERSION).major
+      UI.section('Fully deintegrating due to major version update') do
+        projects = Pathname.glob(config.installation_root + '*.xcodeproj').map { |path| Xcodeproj::Project.open(path) }
+        deintegrator = Deintegrator.new
+        projects.sort.each do |project|
+          deintegrator.deintegrate_project(project)
+          project.save if project.dirty?
+        end
+      end
+    end
+
     # Ensures that all plugins specified in the {#podfile} are loaded.
     #
     # @return [void]

lib/cocoapods/installer/user_project_integrator.rb

@@ -5,8 +5,6 @@ require 'active_support/core_ext/string/inflections'
 require 'active_support/core_ext/array/conversions'
 
 module Pod
-  autoload :Deintegrator, 'cocoapods_deintegrate'
-
   class Installer
     # The {UserProjectIntegrator} integrates the libraries generated by
     # TargetDefinitions of the {Podfile} with their correspondent user