[rubygems/rubygems] Manage global gem cache directly

Previously, it was maintained in sync with the standard cache. That was
less efficient, and it caused some error messages to point to non
existent files.

https://github.com/rubygems/rubygems/commit/931f8cb8a9

lib/bundler/rubygems_gem_installer.rb

@@ -31,7 +31,10 @@ module Bundler
       generate_plugins
 
       write_spec
-      write_cache_file
+
+      SharedHelpers.filesystem_access("#{gem_home}/cache", :write) do
+        write_cache_file
+      end
 
       say spec.post_install_message unless spec.post_install_message.nil?
 

lib/bundler/source/rubygems.rb

@@ -357,7 +357,7 @@ module Bundler
       end
 
       def cached_path(spec)
-        possibilities = @caches.map {|p| "#{p}/#{spec.file_name}" }
+        possibilities = (@caches << download_cache_path(spec)).compact.map {|p| "#{p}/#{spec.file_name}" }
         possibilities.find {|p| File.exist?(p) }
       end
 
@@ -456,9 +456,15 @@ module Bundler
 
         spec.fetch_platform
 
-        download_path = requires_sudo? ? Bundler.tmp(spec.full_name) : rubygems_dir
-        download_cache_path = "#{download_path}/cache"
-        gem_path = "#{default_cache_path}/#{spec.file_name}"
+        cache_path = download_cache_path(spec) || default_cache_path_for(rubygems_dir)
+        gem_path = "#{cache_path}/#{spec.file_name}"
+
+        if requires_sudo?
+          download_path = Bundler.tmp(spec.full_name)
+          download_cache_path = default_cache_path_for(download_path)
+        else
+          download_cache_path = cache_path
+        end
 
         SharedHelpers.filesystem_access(download_cache_path) do |p|
           FileUtils.mkdir_p(p)
@@ -466,7 +472,7 @@ module Bundler
         download_gem(spec, download_cache_path)
 
         if requires_sudo?
-          SharedHelpers.filesystem_access(default_cache_path) do |p|
+          SharedHelpers.filesystem_access(cache_path) do |p|
             Bundler.mkdir_p(p)
           end
           Bundler.sudo "mv #{download_cache_path}/#{spec.file_name} #{gem_path}"
@@ -489,8 +495,8 @@ module Bundler
         Bundler.rubygems.gem_dir
       end
 
-      def default_cache_path
-        "#{rubygems_dir}/cache"
+      def default_cache_path_for(dir)
+        "#{dir}/cache"
       end
 
       def cache_path
@@ -509,38 +515,9 @@ module Bundler
       #         the local directory the .gem will end up in.
       #
       def download_gem(spec, download_cache_path)
-        local_path = File.join(download_cache_path, spec.file_name)
-
-        if (cache_path = download_cache_path(spec)) && cache_path.file?
-          SharedHelpers.filesystem_access(local_path) do
-            FileUtils.cp(cache_path, local_path)
-          end
-        else
-          uri = spec.remote.uri
-          Bundler.ui.confirm("Fetching #{version_message(spec)}")
-          Bundler.rubygems.download_gem(spec, uri, download_cache_path)
-          cache_globally(spec, local_path)
-        end
-      end
-
-      # Checks if the requested spec exists in the global cache. If it does
-      # not, we create the relevant global cache subdirectory if it does not
-      # exist and copy the spec from the local cache to the global cache.
-      #
-      # @param  [Specification] spec
-      #         the spec we want to copy to the global cache.
-      #
-      # @param  [String] local_cache_path
-      #         the local directory from which we want to copy the .gem.
-      #
-      def cache_globally(spec, local_cache_path)
-        return unless cache_path = download_cache_path(spec)
-        return if cache_path.exist?
-
-        SharedHelpers.filesystem_access(cache_path.dirname, &:mkpath)
-        SharedHelpers.filesystem_access(cache_path) do
-          FileUtils.cp(local_cache_path, cache_path)
-        end
+        uri = spec.remote.uri
+        Bundler.ui.confirm("Fetching #{version_message(spec)}")
+        Bundler.rubygems.download_gem(spec, uri, download_cache_path)
       end
 
       # Returns the global cache path of the calling Rubygems::Source object.
@@ -559,7 +536,7 @@ module Bundler
         return unless remote = spec.remote
         return unless cache_slug = remote.cache_slug
 
-        Bundler.user_cache.join("gems", cache_slug, spec.file_name)
+        Bundler.user_cache.join("gems", cache_slug)
       end
 
       def extension_cache_slug(spec)

spec/bundler/install/global_cache_spec.rb

@@ -37,6 +37,18 @@ RSpec.describe "global gem caching" do
       expect(the_bundle).to include_gems "rack 1.0.0"
     end
 
+    it "shows a proper error message if a cached gem is corrupted" do
+      source_global_cache.mkpath
+      FileUtils.touch(source_global_cache("rack-1.0.0.gem"))
+
+      install_gemfile <<-G, :artifice => "compact_index_no_gem", :raise_on_error => false
+        source "#{source}"
+        gem "rack"
+      G
+
+      expect(err).to include("Gem::Package::FormatError: package metadata is missing in #{source_global_cache("rack-1.0.0.gem")}")
+    end
+
     describe "when the same gem from different sources is installed" do
       it "should use the appropriate one from the global cache" do
         install_gemfile <<-G, :artifice => "compact_index"