Auto merge of #5707 - bundler:seg-sort-by-name-spec-set, r=indirect

[SpecSet] Sort by name in #tsort

Closes #5696

This is required for backwards compatibility, see
issue #5696  for an example. The issue is that previous versions of bundler would have the load path in one (correct) order, and master has them in another (correct) order. So some projects depend on the load path ordering when multiple gems have the same requirable file.

- [x] Test case

lib/bundler/spec_set.rb

@@ -160,7 +160,8 @@ def lookup
     end
 
     def tsort_each_node
-      @specs.each {|s| yield s }
+      # MUST sort by name for backwards compatibility
+      @specs.sort_by(&:name).each {|s| yield s }
     end
 
     def spec_for_dependency(dep, match_current_platform)

spec/runtime/setup_spec.rb

@@ -108,6 +108,17 @@
   end
 
   context "load order" do
+    def clean_load_path(lp)
+      without_bundler_load_path = ruby!("puts $LOAD_PATH").split("\n")
+      lp = lp - [
+        bundler_path.to_s,
+        bundler_path.join("gems/bundler-#{Bundler::VERSION}/lib").to_s,
+        tmp("rubygems/lib").to_s,
+        root.join("../lib").expand_path.to_s,
+      ] - without_bundler_load_path
+      lp.map! {|p| p.sub(/^#{system_gem_path}/, "") }
+    end
+
     it "puts loaded gems after -I and RUBYLIB" do
       install_gemfile <<-G
         source "file://#{gem_repo1}"
@@ -139,22 +150,14 @@
         gem "rails"
       G
 
-      without_bundler_load_path = ruby!("puts $LOAD_PATH").split("\n")
-
       ruby! <<-RUBY
         require 'rubygems'
         require 'bundler'
         Bundler.setup
         puts $LOAD_PATH
       RUBY
 
-      load_path = out.split("\n") - [
-        bundler_path.to_s,
-        bundler_path.join("gems/bundler-#{Bundler::VERSION}/lib").to_s,
-        tmp("rubygems/lib").to_s,
-        root.join("../lib").expand_path.to_s,
-      ] - without_bundler_load_path
-      load_path.map! {|lp| lp.sub(/^#{system_gem_path}/, "") }
+      load_path = clean_load_path(out.split("\n"))
 
       expect(load_path).to start_with(
         "/gems/rails-2.3.2/lib",
@@ -166,6 +169,29 @@
         "/gems/rake-10.0.2/lib"
       )
     end
+
+    it "falls back to order the load path alphabetically for backwards compatibility" do
+      install_gemfile! <<-G
+        source "file://#{gem_repo1}"
+        gem "weakling"
+        gem "duradura"
+        gem "terranova"
+      G
+
+      ruby! <<-RUBY
+        require 'rubygems'
+        require 'bundler/setup'
+        puts $LOAD_PATH
+      RUBY
+
+      load_path = clean_load_path(out.split("\n"))
+
+      expect(load_path).to start_with(
+        "/gems/weakling-0.0.3/lib",
+        "/gems/terranova-8/lib",
+        "/gems/duradura-7.0/lib"
+      )
+    end
   end
 
   it "raises if the Gemfile was not yet installed" do