Add a spec for our custom GemFetcher cop

2 files changed, 18 insertions, 9 deletions

diff --git a/rubocop/cop/gem_fetcher.rb b/rubocop/cop/gem_fetcher.rb
index 4a63c760744..c199f6acab2 100644
--- a/rubocop/cop/gem_fetcher.rb
+++ b/rubocop/cop/gem_fetcher.rb
@@ -1,17 +1,15 @@
 module RuboCop
   module Cop
-    # Cop that checks for all gems specified in the Gemfile, and will
-    # alert if any gem is to be fetched not from the RubyGems index.
-    # This enforcement is done so as to minimize external build
-    # dependencies and build times.
+    # This cop prevents usage of the `git` and `github` arguments to `gem` in a
+    # `Gemfile` in order to avoid additional points of failure beyond
+    # rubygems.org.
     class GemFetcher < RuboCop::Cop::Cop
       MSG = 'Do not use gems from git repositories, only use gems from RubyGems.'
 
       GIT_KEYS = [:git, :github]
 
       def on_send(node)
-        file_path = node.location.expression.source_buffer.name
-        return unless file_path.end_with?("Gemfile")
+        return unless gemfile?(node)
 
         func_name = node.children[1]
         return unless func_name == :gem
@@ -19,10 +17,21 @@ module RuboCop
         node.children.last.each_node(:pair) do |pair|
           key_name = pair.children[0].children[0].to_sym
           if GIT_KEYS.include?(key_name)
-            add_offense(node, :selector)
+            add_offense(node, pair.source_range, MSG)
           end
         end
       end
+
+      private
+
+      def gemfile?(node)
+        node
+          .location
+          .expression
+          .source_buffer
+          .name
+          .end_with?("Gemfile")
+      end
     end
   end
 end
diff --git a/rubocop/rubocop.rb b/rubocop/rubocop.rb
index 3e292a4527c..aa35fb1701c 100644
--- a/rubocop/rubocop.rb
+++ b/rubocop/rubocop.rb
@@ -1,4 +1,4 @@
-require_relative 'cop/migration/add_index'
+require_relative 'cop/gem_fetcher'
 require_relative 'cop/migration/add_column'
 require_relative 'cop/migration/add_column_with_default'
-require_relative 'cop/gem_fetcher'
+require_relative 'cop/migration/add_index'