Add flag to treat all warnings as errors

lib/danger/danger_periphery.rb

@@ -29,6 +29,12 @@ class DangerPeriphery < Plugin
     #                   By default +false+ is set.
     attr_accessor :scan_all_files
 
+    # A flag to treat warnings as errors.
+    # @return [Boolean] +true+ if this plugin reports all violations as errors.
+    #                   Otherwise +false+, it reports violations as warnings.
+    #                   By default +false+ is set.
+    attr_accessor :warning_as_error
+
     # For internal use only.
     #
     # @return [Symbol]
@@ -42,6 +48,7 @@ class DangerPeriphery < Plugin
     def initialize(dangerfile)
       super(dangerfile)
       @format = :checkstyle
+      @warning_as_error = false
     end
 
     # Scans Swift files.
@@ -75,7 +82,7 @@ def scan(options = {})
 
         next if block_given? && !yield(entry)
 
-        warn(entry.message, file: entry.path, line: entry.line)
+        report(entry.message, file: entry.path, line: entry.line)
       end
     end
 
@@ -94,6 +101,12 @@ def install(version: :latest, path: 'periphery', force: false)
 
     private
 
+    def report(*args, **kwargs)
+      return fail(*args, **kwargs) if warning_as_error
+
+      warn(*args, **kwargs)
+    end
+
     def files_in_diff
       # Taken from https://github.com/ashfurrow/danger-ruby-swiftlint/blob/5184909aab00f12954088684bbf2ce5627e08ed6/lib/danger_plugin.rb#L214-L216
       renamed_files_hash = git.renamed_files.to_h { |rename| [rename[:before], rename[:after]] }

spec/danger/danger_periphery_spec.rb

@@ -137,6 +137,39 @@
     end
   end
 
+  describe '#warning_as_error' do
+    subject(:errors) { dangerfile.status_report[:errors] }
+
+    before do
+      periphery.warning_as_error = warning_as_error
+      periphery.scan
+    end
+
+    context 'with false' do
+      let(:warning_as_error) { false }
+
+      it 'reports violations as warnings' do
+        expect(warnings).not_to be_empty
+      end
+
+      it 'does not report any errors' do
+        expect(errors).to be_empty
+      end
+    end
+
+    context 'with true' do
+      let(:warning_as_error) { true }
+
+      it 'reports violations as errors' do
+        expect(errors).not_to be_empty
+      end
+
+      it 'does not warn anything' do
+        expect(warnings).to be_empty
+      end
+    end
+  end
+
   describe '#format' do
     subject(:parser) { periphery.send(:parser) }