Refactor SimpleCov result/report generator

.simplecov

@@ -2,16 +2,9 @@
 # see https://github.com/colszowka/simplecov/blob/master/lib/simplecov/defaults.rb
 # vim: set ft=ruby
 
-## DEFINE VARIABLES
-@minimum_coverage = 100.0
 ENV['FULL_BUILD'] ||= ENV['CI']
-@running_ci       = !!(ENV['FULL_BUILD'] =~ /\Atrue\z/i)
-@generate_report  = @running_ci || !!(ENV['COVERAGE'] =~ /\Atrue\z/i)
-@output = STDOUT
-# rubocop:enable Style/DoubleNegation
 
 ## CONFIGURE SIMPLECOV
-
 SimpleCov.profiles.define 'app' do
   coverage_dir 'coverage'
   load_profile 'test_frameworks'
@@ -35,18 +28,21 @@ SimpleCov.profiles.define 'app' do
   add_filter '/.bundle/'
 end
 
-if @generate_report
-  SimpleCov.start 'app'
-  if @running_ci
-    require 'codeclimate-test-reporter'
-    @output.puts '[COVERAGE] Running with SimpleCov Simple Formatter and CodeClimate Test Reporter'
-    formatters = [
-      SimpleCov::Formatter::SimpleFormatter,
-      CodeClimate::TestReporter::Formatter
-    ]
-  else
-    @output.puts '[COVERAGE] Running with SimpleCov HTML Formatter'
-    formatters = [SimpleCov::Formatter::HTMLFormatter]
+generate_report = !!(ENV['COVERAGE'] =~ /\Atrue\z/i)
+running_ci = !!(ENV['FULL_BUILD'] =~ /\Atrue\z/i)
+generate_result = running_ci || generate_report
+require_relative 'scripts/coverage_report'
+reporter = CoverageReport.new
+if generate_report
+  reporter.configure_to_generate_report!
+  SimpleCov.at_exit do
+    reporter.generate_report!
   end
-  SimpleCov.formatters = formatters
 end
+if generate_result
+  # only start when generating a result
+  SimpleCov.start 'app'
+  STDERR.puts '[COVERAGE] Running'
+  reporter.configure_to_generate_result!
+end
+SimpleCov.formatters = reporter.formatters

scripts/coverage_report.rb

@@ -0,0 +1,88 @@
+#!/usr/bin/env ruby
+
+require 'json'
+class CoverageReport
+  attr_reader :formatters
+
+  def initialize
+    @formatters = []
+  end
+
+  def configure_to_generate_result!
+    SimpleCov.configure do
+      # use_merging   true
+      minimum_coverage 0.0 # disable
+      maximum_coverage_drop 100.0 # disable
+    end
+    SimpleCov.at_exit do
+      STDERR.puts "[COVERAGE] creating #{File.join(SimpleCov.coverage_dir, '.resultset.json')}"
+      SimpleCov.result.format!
+    end
+  end
+
+  def configure_to_generate_report!
+    @minimum_coverage = ENV.fetch('COVERAGE_MINIMUM') { 100.0 }.to_f.round(2)
+    SimpleCov.configure do
+      minimum_coverage @minimum_coverage
+      # minimum_coverage_by_file 60
+      # maximum_coverage_drop 1
+      refuse_coverage_drop
+    end
+
+    @formatters = [SimpleCov::Formatter::HTMLFormatter]
+  end
+
+  def generate_report!
+    report_dir = SimpleCov.coverage_dir
+    file = File.join(report_dir, '.resultset.json')
+    if File.exist?(file)
+      json = JSON.parse(File.read(file))
+      result = SimpleCov::Result.from_hash(json)
+      results = [result]
+      merged_result = SimpleCov::ResultMerger.merge_results(*results)
+      merged_result.format!
+      STDERR.puts "[COVERAGE] merged #{file}; processing..."
+      process_result(merged_result)
+    else
+      abort "No files found to report: #{Dir.glob(report_dir)}"
+    end
+  end
+
+  # https://github.com/colszowka/simplecov/blob/v0.14.1/lib/simplecov/defaults.rb#L71-L98
+  def process_result(result)
+    @exit_status = SimpleCov::ExitCodes::SUCCESS
+    covered_percent = result.covered_percent.round(2)
+    covered_percentages = result.covered_percentages.map { |p| p.round(2) }
+
+    if @exit_status == SimpleCov::ExitCodes::SUCCESS # No other errors
+      if covered_percent < SimpleCov.minimum_coverage # rubocop:disable Metrics/BlockNesting
+        $stderr.printf("Coverage (%.2f%%) is below the expected minimum coverage (%.2f%%).\n", covered_percent, SimpleCov.minimum_coverage)
+        @exit_status = SimpleCov::ExitCodes::MINIMUM_COVERAGE
+      elsif covered_percentages.any? { |p| p < SimpleCov.minimum_coverage_by_file } # rubocop:disable Metrics/BlockNesting
+        $stderr.printf("File (%s) is only (%.2f%%) covered. This is below the expected minimum coverage per file of (%.2f%%).\n", result.least_covered_file, covered_percentages.min, SimpleCov.minimum_coverage_by_file)
+        @exit_status = SimpleCov::ExitCodes::MINIMUM_COVERAGE
+      elsif (last_run = SimpleCov::LastRun.read) # rubocop:disable Metrics/BlockNesting
+        coverage_diff = last_run["result"]["covered_percent"] - covered_percent
+        if coverage_diff > SimpleCov.maximum_coverage_drop # rubocop:disable Metrics/BlockNesting
+          $stderr.printf("Coverage has dropped by %.2f%% since the last time (maximum allowed: %.2f%%).\n", coverage_diff, SimpleCov.maximum_coverage_drop)
+          @exit_status = SimpleCov::ExitCodes::MAXIMUM_COVERAGE_DROP
+        end
+      end
+    end
+
+    # Don't overwrite last_run file if refuse_coverage_drop option is enabled and the coverage has dropped
+    unless @exit_status == SimpleCov::ExitCodes::MAXIMUM_COVERAGE_DROP
+      SimpleCov::LastRun.write(:result => {:covered_percent => covered_percent})
+    end
+
+    # Force exit with stored status (see github issue #5)
+    # unless it's nil or 0 (see github issue #281)
+    Kernel.exit @exit_status if @exit_status && @exit_status > 0
+  end
+end
+if __FILE__ == $0
+  require 'simplecov'
+  reporter = CoverageReport.new
+  reporter.configure_to_generate_report!
+  reporter.generate_report!
+end