codeclimate · dblandin · Nov 7, 2016 · Oct 18, 2016 · Oct 21, 2016 · Oct 29, 2016
diff --git a/README.md b/README.md
@@ -40,13 +40,13 @@ engines:
 
 This will tell the duplication engine to analyze Ruby and JavaScript files.
 
-### Threshold
+### Mass Threshold
 
 We set useful threshold defaults for the languages we support but you may want
 to adjust these settings based on your project guidelines.
 
-The threshold configuration represents the minimum "mass" a code block must have
-to be analyzed for duplication. If the engine is too easily reporting
+The mass threshold configuration represents the minimum "mass" a code block must
+have to be analyzed for duplication. If the engine is too easily reporting
 duplication, try raising the threshold. If you suspect that the engine isn't
 catching enough duplication, try lowering the threshold. The best setting tends
 to differ from language to language.
@@ -68,6 +68,29 @@ engines:
 Note that you have the update the YAML structure under the `languages` key to
 the Hash type to support extra configuration.
 
+### Count Threshold
+
+By default, the duplication engine will report code that has been duplicated in just two locations. You can be less strict by only raising a warning if code is duplicated in three or more locations only. To adjust this setting, add a `count_threshold` key to your config. For instance, to use the default `mass_threshold` for ruby, but to enforce the [Rule of Three][rule-of-three], you could use this configuration:
+
+```yaml
+engines:
+  duplication:
+    enabled: true
+    config:
+      languages:
+        ruby:
+          count_threshold: 3
+```
+
+You can also change the default count_threshold for all languages:
+
+```yaml
+engines:
+  duplication:
+    enabled: true
+    count_threshold: 3
+```
+
 ### Excluding files and directories
 
 As with any other Code Climate engine, you can exclude certain files or
@@ -86,4 +109,5 @@ engines:
 [what-is-duplication]: https://docs.codeclimate.com/docs/duplication-concept
 [flay]: https://github.com/seattlerb/flay
 [cli]: https://github.com/codeclimate/codeclimate
+[rule-of-three]: https://en.wikipedia.org/wiki/Rule_of_three_(computer_programming)
 [exclude-files-engine]: https://docs.codeclimate.com/docs/excluding-files-and-folders#section-exclude-paths-for-specific-engines
diff --git a/lib/cc/engine/analyzers/analyzer_base.rb b/lib/cc/engine/analyzers/analyzer_base.rb
@@ -43,6 +43,10 @@ def mass_threshold
           engine_config.mass_threshold_for(self.class::LANGUAGE) || self.class::DEFAULT_MASS_THRESHOLD
         end
 
+        def count_threshold
+          engine_config.count_threshold_for(self.class::LANGUAGE)
+        end
+
         def calculate_points(mass)
           overage = mass - mass_threshold
           base_points + (overage * points_per_overage)

diff --git a/lib/cc/engine/analyzers/engine_config.rb b/lib/cc/engine/analyzers/engine_config.rb
@@ -2,6 +2,8 @@ module CC
   module Engine
     module Analyzers
       class EngineConfig
+        DEFAULT_COUNT_THRESHOLD = 2
+
         def initialize(hash)
           @config = normalize(hash)
         end
@@ -30,6 +32,16 @@ def mass_threshold_for(language)
           end
         end
 
+        def count_threshold_for(language)
+          threshold = fetch_language(language)["count_threshold"] ||
+            config.fetch("config", {}).fetch("count_threshold", nil) ||
+            DEFAULT_COUNT_THRESHOLD
+
+          if threshold
+            threshold.to_i
+          end
+        end
+
         def fetch_language(language)
           language = config.
             fetch("languages", {}).

diff --git a/lib/cc/engine/analyzers/reporter.rb b/lib/cc/engine/analyzers/reporter.rb
@@ -51,6 +51,7 @@ def report
             violations = new_violations(issue)
 
             violations.each do |violation|
+              next if (violation.occurrences + 1) < language_strategy.count_threshold
               debug("Violation name=#{violation.report_name} mass=#{violation.mass}")
 
               unless reports.include?(violation.report_name)

diff --git a/lib/cc/engine/analyzers/violation.rb b/lib/cc/engine/analyzers/violation.rb
@@ -35,6 +35,10 @@ def mass
           current_sexp.mass
         end
 
+        def occurrences
+          other_sexps.count
+        end
+
         private
 
         attr_reader :language_strategy, :other_sexps, :current_sexp
@@ -96,10 +100,6 @@ def description
           description += " (mass = #{mass})"
           description
         end
-
-        def occurrences
-          other_sexps.count
-        end
       end
     end
   end

diff --git a/spec/cc/engine/analyzers/engine_config_spec.rb b/spec/cc/engine/analyzers/engine_config_spec.rb
@@ -75,6 +75,47 @@
     end
   end
 
+  describe "count_threshold_for" do
+    it "returns configured count threshold as integer" do
+      engine_config = CC::Engine::Analyzers::EngineConfig.new({
+        "config" => {
+          "languages" => {
+            "EliXiR" => {
+              "count_threshold" => "3",
+            },
+          },
+        },
+      })
+
+      expect(engine_config.count_threshold_for("elixir")).to eq(3)
+    end
+
+    it "returns default value when language value is empty" do
+      engine_config = CC::Engine::Analyzers::EngineConfig.new({
+        "config" => {
+          "count_threshold" => "4",
+          "languages" => {
+            "ruby" => "",
+          },
+        },
+      })
+
+      expect(engine_config.count_threshold_for("ruby")).to eq(4)
+    end
+
+    it "returns 2 by default" do
+      engine_config = CC::Engine::Analyzers::EngineConfig.new({
+        "config" => {
+          "languages" => {
+            "ruby" => "",
+          },
+        },
+      })
+
+      expect(engine_config.count_threshold_for("ruby")).to eq(2)
+    end
+  end
+
   describe "include_paths" do
     it "returns given include paths" do
       engine_config = CC::Engine::Analyzers::EngineConfig.new({