Lint in parallel (#118)

* Lint in parallel

* Synced output for dot/flycheck formatters

* Re-raise exceptions raised in fibers

* Add readme instructions

spec/ameba/runner_spec.cr

@@ -53,6 +53,19 @@ module Ameba
         Runner.new(all_rules, [source], formatter, default_severity).run.success?.should be_true
       end
 
+      context "exception in rule" do
+        it "raises an exception raised in fiber while running a rule" do
+          rule = RaiseRule.new
+          rule.should_raise = true
+          rules = [rule] of Rule::Base
+          source = Source.new "", "source.cr"
+
+          expect_raises(Exception, "something went wrong") do
+            Runner.new(rules, [source], formatter, default_severity).run
+          end
+        end
+      end
+
       context "invalid syntax" do
         it "reports a syntax error" do
           rules = [Rule::Lint::Syntax.new] of Rule::Base

spec/spec_helper.cr

@@ -81,6 +81,15 @@ module Ameba
     end
   end
 
+  # A rule that always raises an error
+  struct RaiseRule < Rule::Base
+    property should_raise = false
+
+    def test(source)
+      should_raise && raise "something went wrong"
+    end
+  end
+
   class DummyFormatter < Formatter::BaseFormatter
     property started_sources : Array(Source)?
     property finished_sources : Array(Source)?