Auto merge of #5336 - bundler:seg-installation-failure-reason, r=indi…

…rect

[ParallelInstaller] Print out why a gem needed to be installed if ins…

…tallation fails

I think this will close #5078 by making it easier to understand why a gem needed to be installed, especially in the case when the user can't just look in the lockfile

lib/bundler/installer/parallel_installer.rb

@@ -90,6 +90,7 @@ def initialize(installer, all_specs, size, standalone, force)
       @standalone = standalone
       @force = force
       @specs = all_specs.map {|s| SpecInstallation.new(s) }
+      @spec_set = all_specs
     end
 
     def call
@@ -116,7 +117,7 @@ def worker_pool
           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 @@ def check_for_corrupt_lockfile
       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

lib/bundler/spec_set.rb

@@ -118,6 +118,13 @@ def find_by_name_and_platform(name, platform)
       @specs.detect {|spec| spec.name == name && spec.match_platform(platform) }
     end
 
+    def what_required(spec)
+      unless req = find {|s| s.dependencies.any? {|d| d.type == :runtime && d.name == spec.name } }
+        return [spec]
+      end
+      what_required(req) << spec
+    end
+
   private
 
     def sorted

spec/install/failure_spec.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+require "spec_helper"
+
+RSpec.describe "bundle install" do
+  context "installing a gem fails" do
+    it "prints out why that gem was being installed" do
+      build_repo2 do
+        build_gem "activesupport", "2.3.2" do |s|
+          s.extensions << "Rakefile"
+          s.write "Rakefile", <<-RUBY
+            task :default do
+              abort "make installing activesupport-2.3.2 fail"
+            end
+          RUBY
+        end
+      end
+
+      install_gemfile <<-G
+        source "file:#{gem_repo2}"
+        gem "rails"
+      G
+      expect(out).to end_with(<<-M.strip)
+An error occurred while installing activesupport (2.3.2), and Bundler cannot continue.
+Make sure that `gem install activesupport -v '2.3.2'` succeeds before bundling.
+
+In Gemfile:
+  rails was resolved to 2.3.2, which depends on
+    actionmailer was resolved to 2.3.2, which depends on
+      activesupport
+                     M
+    end
+  end
+end

spec/install/gemfile/git_spec.rb

@@ -1085,7 +1085,12 @@
         gem "foo", :git => "#{lib_path("foo-1.0")}"
       G
 
-      expect(out).to include("An error occurred while installing foo (1.0)")
+      expect(out).to end_with(<<-M.strip)
+An error occurred while installing foo (1.0), and Bundler cannot continue.
+
+In Gemfile:
+  foo
+      M
       expect(out).not_to include("gem install foo")
     end