Merge pull request #2679 from jendiamond/same_gem_twice_boo

warn if the same gem (same version) is added twice

2 files changed, 18 insertions, 3 deletions

diff --git a/lib/bundler/dsl.rb b/lib/bundler/dsl.rb
index 947aca7ba8..6d4d1e70e8 100644
--- a/lib/bundler/dsl.rb
+++ b/lib/bundler/dsl.rb
@@ -83,10 +83,14 @@ module Bundler
           elsif dep.type == :development
             return
           else
-            raise GemfileError, "You cannot specify the same gem twice with different version requirements. \n" \
-                            "You specified: #{current.name} (#{current.requirement}) and " \
-                            "#{dep.name} (#{dep.requirement})\n"
+            raise GemfileError, "You cannot specify the same gem twice with different version requirements.\n" \
+                            "You specified: #{current.name} (#{current.requirement}) and #{dep.name} (#{dep.requirement})"
           end
+
+        else
+          Bundler.ui.warn "Your Gemfile lists the gem #{current.name} (#{current.requirement}) more than once.\n" \
+                          "You should probably keep only one of them.\n" \
+                          "While it's not a problem now, it could cause errors if you change the version of just one of them later."
         end
 
         if current.source != dep.source
diff --git a/spec/install/gems/simple_case_spec.rb b/spec/install/gems/simple_case_spec.rb
index 630ea083c1..b453975399 100644
--- a/spec/install/gems/simple_case_spec.rb
+++ b/spec/install/gems/simple_case_spec.rb
@@ -832,4 +832,15 @@ describe "bundle install with gem sources" do
     bundle :install, :artifice => 'endpoint_marshal_fail' # force gemspec load
     should_be_installed "activesupport 2.3.2"
   end
+
+  describe "#gem" do
+    it "will display a Warning if the gem is duplicated" do
+      gemfile <<-G
+        gem 'rails', '~> 4.0.0'
+        gem 'rails', '~> 4.0.0'
+      G
+      bundle :install
+      expect(out).to include("more than once")
+    end
+  end
 end