Optimize cleaning dirs during installation

lib/cocoapods/downloader.rb

@@ -51,8 +51,7 @@ def self.download(
       if target && result.location && target != result.location
         UI.message "Copying #{request.name} from `#{result.location}` to #{UI.path target}", '> ' do
           Cache.read_lock(result.location) do
-            FileUtils.rm_rf target
-            FileUtils.cp_r(result.location, target)
+            FileUtils.cp_r(result.location, target, :remove_destination => true)
           end
         end
       end

lib/cocoapods/downloader/cache.rb

@@ -235,13 +235,38 @@ def cached_spec(request)
       #         was not found in the download cache.
       #
       def uncached_pod(request)
-        in_tmpdir do |target|
-          result, podspecs = download(request, target)
+        in_tmpdir do |tmp_dir|
+          result, podspecs = download(request, tmp_dir)
           result.location = nil
 
-          podspecs.each do |name, spec|
+          # Split by pods that require a prepare command or not to speed up installation.
+          no_prep_cmd_specs, prep_cmd_specs = podspecs.partition { |_, spec| spec.prepare_command.nil? }.map(&:to_h)
+
+          # Pods with a prepare command currently copy the entire repo, run the prepare command against the whole
+          # repo and then clean it up. We configure those first to ensure the repo is pristine.
+          prep_cmd_specs.each do |name, spec|
             destination = path_for_pod(request, :name => name, :params => result.checkout_options)
-            copy_and_clean(target, destination, spec)
+            copy_source_and_clean(tmp_dir, destination, spec)
+            write_spec(spec, path_for_spec(request, :name => name, :params => result.checkout_options))
+            if request.name == name
+              result.location = destination
+            end
+          end
+
+          specs_by_platform = group_subspecs_by_platform(no_prep_cmd_specs.values)
+
+          # Remaining pods without a prepare command can be optimized by cleaning the repo first
+          # and then copying only the files needed for all pods being downloaded.
+          pod_dir_cleaner = Sandbox::PodDirCleaner.new(tmp_dir, specs_by_platform)
+          Cache.write_lock(tmp_dir) do
+            pod_dir_cleaner.clean!
+          end
+
+          no_prep_cmd_specs.each do |name, spec|
+            destination = path_for_pod(request, :name => name, :params => result.checkout_options)
+            file_accessors = pod_dir_cleaner.file_accessors.select { |fa| fa.spec.name == spec.name }
+            files = Pod::Sandbox::FileAccessor.all_files(file_accessors).map(&:to_s)
+            copy_files(files, tmp_dir, destination, spec)
             write_spec(spec, path_for_spec(request, :name => name, :params => result.checkout_options))
             if request.name == name
               result.location = destination
@@ -279,23 +304,58 @@ def in_tmpdir(&blk)
       #
       # @return [Void]
       #
-      def copy_and_clean(source, destination, spec)
-        specs_by_platform = group_subspecs_by_platform(spec)
+      def copy_source_and_clean(source, destination, spec)
+        specs_by_platform = group_subspecs_by_platform([spec])
         destination.parent.mkpath
         Cache.write_lock(destination) do
-          FileUtils.rm_rf(destination)
-          FileUtils.cp_r(source, destination)
+          FileUtils.cp_r(source, destination, :remove_destination => true)
           Pod::Installer::PodSourcePreparer.new(spec, destination).prepare!
           Sandbox::PodDirCleaner.new(destination, specs_by_platform).clean!
         end
       end
 
-      def group_subspecs_by_platform(spec)
+      # Copies the `files` from the `source` directory to `destination`, _without_ cleaning the directory
+      # of any files unused by `spec`. This is a faster version used when installing pods without
+      # a prepare command.
+      #
+      # @param  [Array<Pathname>] files
+      #
+      # @param  [Pathname] source
+      #
+      # @param  [Pathname] destination
+      #
+      # @param  [Specification] spec
+      #
+      # @return [Void]
+      #
+      def copy_files(files, source, destination, spec)
+        destination.mkpath
+        files = files.reject { |f| !File.exist?(f) }
+        Cache.write_lock(destination) do
+          FileUtils.rm_rf(destination)
+          files_by_dir = files.group_by do |file|
+            relative_path = Pathname(file).relative_path_from(Pathname(source)).to_s
+            destination_path = File.join(destination, relative_path)
+            File.dirname(destination_path)
+          end
+
+          files_by_dir.each do |dir, files_to_copy|
+            FileUtils.mkdir_p(dir)
+            FileUtils.cp_r(files_to_copy, dir)
+          end
+
+          Pod::Installer::PodSourcePreparer.new(spec, destination).prepare!
+        end
+      end
+
+      def group_subspecs_by_platform(specs)
         specs_by_platform = {}
-        [spec, *spec.recursive_subspecs].each do |ss|
-          ss.available_platforms.each do |platform|
-            specs_by_platform[platform] ||= []
-            specs_by_platform[platform] << ss
+        specs.each do |spec|
+          [spec, *spec.recursive_subspecs].each do |ss|
+            ss.available_platforms.each do |platform|
+              specs_by_platform[platform] ||= []
+              specs_by_platform[platform] << ss
+            end
           end
         end
         specs_by_platform

lib/cocoapods/sandbox/pod_dir_cleaner.rb

@@ -15,11 +15,9 @@ def initialize(root, specs_by_platform)
       # @return [void]
       #
       def clean!
-        clean_paths.each { |path| FileUtils.rm_rf(path) } if root.exist?
+        FileUtils.rm_rf(clean_paths) if root.exist?
       end
 
-      private
-
       # @return [Array<Sandbox::FileAccessor>] the file accessors for all the
       #         specifications on their respective platform.
       #
@@ -29,6 +27,8 @@ def file_accessors
         end
       end
 
+      private
+
       # @return [Sandbox::PathList] The path list for this Pod.
       #
       def path_list

spec/unit/downloader/cache_spec.rb

@@ -49,7 +49,7 @@ module Pod
         end
       end
 
-      @cache.send(:group_subspecs_by_platform, @spec).should == {
+      @cache.send(:group_subspecs_by_platform, [@spec]).should == {
         Platform.new(:ios, '8.0') => [@spec.subspecs.first],
         Platform.new(:ios, '6.0') => [@spec],
         Platform.new(:osx, '10.7') => [@spec],
@@ -81,7 +81,7 @@ module Pod
         end
 
         it 'downloads the source' do
-          @cache.expects(:copy_and_clean).twice
+          @cache.expects(:copy_files).twice
           response = @cache.download_pod(@unreleased_request)
           response.should == Downloader::Response.new(@cache.root + @unreleased_request.slug, @spec, @spec.source)
         end