[Cache] Keep files needed by subspecs that have a higher minimum deployment target than root spec

CHANGELOG.md

@@ -4,6 +4,16 @@ To install or update CocoaPods see this [guide](http://docs.cocoapods.org/guides
 
 To install release candidates run `[sudo] gem install cocoapods --pre`
 
+## Master
+
+##### Bug Fixes
+
+* Handle caching specs that have subspecs with higher minimum deployment targets
+  without deleting needed source files.  
+  [Samuel Giddins](https://github.com/segiddins)
+  [#3471](https://github.com/CocoaPods/CocoaPods/issues/3471)
+
+
 ## 0.37.0.rc.1
 
 [Core](https://github.com/CocoaPods/Core/compare/0.37.0.beta.1...0.37.0.rc.1)

lib/cocoapods/downloader/cache.rb

@@ -182,16 +182,24 @@ module Pod
       # @return [Void]
       #
       def copy_and_clean(source, destination, spec)
-        specs_by_platform = {}
-        spec.available_platforms.each do |platform|
-          specs_by_platform[platform] = [spec, *spec.recursive_subspecs].select { |ss| ss.supported_on_platform?(platform) }
-        end
+        specs_by_platform = group_subspecs_by_platform(spec)
         destination.parent.mkpath
         FileUtils.cp_r(source, destination)
         Pod::Installer::PodSourcePreparer.new(spec, destination).prepare!
         Sandbox::PodDirCleaner.new(destination, specs_by_platform).clean!
       end
 
+      def group_subspecs_by_platform(spec)
+        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
+          end
+        end
+        specs_by_platform
+      end
+
       # Writes the given `spec` to the given `path`.
       #
       # @param  [Specification] spec

spec/unit/downloader/cache_spec.rb

@@ -24,6 +24,23 @@ module Pod
       @cache.root.should.be.directory?
     end
 
+    it 'groups subspecs by platform' do
+      @spec = Specification.new do |s|
+        s.ios.deployment_target = '6.0'
+        s.osx.deployment_target = '10.7'
+
+        s.subspec 'subspec' do |ss|
+          ss.ios.deployment_target = '8.0'
+        end
+      end
+
+      @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],
+      }
+    end
+
     describe 'when the download is not cached' do
       describe 'when downloading a released pod' do
         it 'downloads the source' do