[ParallelInstaller] Print out why a gem needed to be installed if installation fails

1 files changed, 15 insertions, 1 deletions

diff --git a/lib/bundler/installer/parallel_installer.rb b/lib/bundler/installer/parallel_installer.rb
index b1a997f3f2..97c124e015 100644
--- a/lib/bundler/installer/parallel_installer.rb
+++ b/lib/bundler/installer/parallel_installer.rb
@@ -90,6 +90,7 @@ module Bundler
       @standalone = standalone
       @force = force
       @specs = all_specs.map {|s| SpecInstallation.new(s) }
+      @spec_set = all_specs
     end
 
     def call
@@ -116,7 +117,7 @@ module Bundler
           spec_install.post_install_message = message
         elsif !success
           spec_install.state = :failed
-          spec_install.error = message
+          spec_install.error = "#{message}\n\n#{require_tree_for_spec(spec_install.spec)}"
         end
         spec_install
       }
@@ -166,6 +167,19 @@ module Bundler
       Bundler.ui.warn(warning.join("\n"))
     end
 
+    def require_tree_for_spec(spec)
+      tree = @spec_set.what_required(spec)
+      t = String.new("In #{File.basename(SharedHelpers.default_gemfile)}:\n")
+      tree.each_with_index do |s, depth|
+        t << "  " * depth.succ << s.name
+        unless tree.last == s
+          t << %( was resolved to #{s.version}, which depends on)
+        end
+        t << %(\n)
+      end
+      t
+    end
+
     # Keys in the remains hash represent uninstalled gems specs.
     # We enqueue all gem specs that do not have any dependencies.
     # Later we call this lambda again to install specs that depended on