Improve tests and helper

  - Add  more tests

  - Use telemetry_labels in danger file
  - Revert test change

ee/lib/ee/gitlab/usage_data.rb

@@ -227,7 +227,10 @@ module EE
                                                                :creator_id,
                                                                start: user_minimum_id,
                                                                finish: user_maximum_id),
-            protected_branches: distinct_count(::Project.with_protected_branches.where(time_period), :creator_id, start: user_minimum_id, finish: user_maximum_id),
+            protected_branches: distinct_count(::Project.with_protected_branches.where(time_period),
+                                               :creator_id,
+                                               start: user_minimum_id,
+                                               finish: user_maximum_id),
             suggestions: distinct_count(::Note.with_suggestions.where(time_period),
                                         :author_id,
                                         start: user_minimum_id,

lib/gitlab/danger/helper.rb

@@ -34,6 +34,18 @@ module Gitlab
           .sort
       end
 
+      # Returns a string containing changed lines as git diff
+      #
+      # Considering changing a line in lib/gitlab/usage_data.rb it will return:
+      #
+      # [ "--- a/lib/gitlab/usage_data.rb",
+      #   "+++ b/lib/gitlab/usage_data.rb",
+      #   "+      # Test change",
+      #   "-      # Old change" ]
+      def changed_lines(changed_file)
+        git.diff_for_file(changed_file).patch.split("\n").select { |line| %r{^[+-]}.match?(line) }
+      end
+
       def all_ee_changes
         all_changed_files.grep(%r{\Aee/})
       end
@@ -77,10 +89,19 @@ module Gitlab
         end
       end
 
-      # Determines the categories a file is in, e.g., `[:frontend]`, `[:backend]`, or  `%i[frontend engineering_productivity]`.
+      # Determines the categories a file is in, e.g., `[:frontend]`, `[:backend]`, or  `%i[frontend engineering_productivity]`
+      # using filename regex and specific change regex if given.
+      #
       # @return Array<Symbol>
       def categories_for_file(file)
-        _, categories = CATEGORIES.find { |regexp, _| regexp.match?(file) }
+        _, categories = CATEGORIES.find do |key, _|
+          filename_regex, changes_regex = Array(key)
+
+          found = filename_regex.match?(file)
+          found &&= changed_lines(file).any? { |changed_line| changes_regex.match?(changed_line) } if changes_regex
+
+          found
+        end
 
         Array(categories || :unknown)
       end
@@ -102,6 +123,8 @@ module Gitlab
       }.freeze
       # First-match win, so be sure to put more specific regex at the top...
       CATEGORIES = {
+        [%r{usage_data}, %r{^(\+|-).*(count|distinct_count)\(.*\)(.*)$}] => [:database, :backend],
+
         %r{\Adoc/.*(\.(md|png|gif|jpg))\z} => :docs,
         %r{\A(CONTRIBUTING|LICENSE|MAINTENANCE|PHILOSOPHY|PROCESS|README)(\.md)?\z} => :docs,
 

spec/lib/gitlab/danger/helper_spec.rb

@@ -166,7 +166,12 @@ RSpec.describe Gitlab::Danger::Helper do
   end
 
   describe '#categories_for_file' do
+    before do
+      allow(fake_git).to receive(:diff_for_file).with('usage_data.rb') { double(:diff, patch: "+ count(User.active)") }
+    end
+
     where(:path, :expected_categories) do
+      'usage_data.rb'   | [:database, :backend]
       'doc/foo.md'      | [:docs]
       'CONTRIBUTING.md' | [:docs]
       'LICENSE'         | [:docs]
@@ -287,6 +292,26 @@ RSpec.describe Gitlab::Danger::Helper do
 
       it { is_expected.to eq(expected_categories) }
     end
+
+    context 'having specific changes' do
+      it 'has database and backend categories' do
+        allow(fake_git).to receive(:diff_for_file).with('usage_data.rb') { double(:diff, patch: "+ count(User.active)") }
+
+        expect(helper.categories_for_file('usage_data.rb')).to eq([:database, :backend])
+      end
+
+      it 'has backend category' do
+        allow(fake_git).to receive(:diff_for_file).with('usage_data.rb') { double(:diff, patch: "+ alt_usage_data(User.active)") }
+
+        expect(helper.categories_for_file('usage_data.rb')).to eq([:backend])
+      end
+
+      it 'has backend category for changes outside usage_data files' do
+        allow(fake_git).to receive(:diff_for_file).with('user.rb') { double(:diff, patch: "+ count(User.active)") }
+
+        expect(helper.categories_for_file('user.rb')).to eq([:backend])
+      end
+    end
   end
 
   describe '#label_for_category' do