Stop rescuing all exceptions.

We do want to generally rescue `Exception` and
any subclasses but there are a few exceptions
we should not rescue. For example, if we rescue
`SystemExit`, it prevents `exit` from exiting.

Fixes #2058.

.rubocop.yml

@@ -51,3 +51,6 @@ Style/RaiseArgs:
     - lib/rspec/core/hooks.rb
     - lib/rspec/core/option_parser.rb
     - lib/rspec/core/pending.rb
+
+RescueException:
+  Enabled: true

lib/rspec/core.rb

@@ -178,4 +178,12 @@ def self.const_missing(name)
     require MODULES_TO_AUTOLOAD.fetch(name) { return super }
     ::RSpec.const_get(name)
   end
+
+  module NonPassthroughExceptions
+    PASSTHROUGH_EXCEPTIONS = [NoMemoryError, SignalException, Interrupt, SystemExit]
+
+    def self.===(exception)
+      PASSTHROUGH_EXCEPTIONS.none? { |pe| pe === exception }
+    end
+  end
 end

lib/rspec/core/configuration.rb

@@ -1735,7 +1735,7 @@ def define_built_in_hooks
         around(:example, :aggregate_failures => true) do |procsy|
           begin
             aggregate_failures(nil, :hide_backtrace => true, &procsy)
-          rescue Exception => exception
+          rescue NonPassthroughExceptions => exception
             procsy.example.set_aggregate_failures_exception(exception)
           end
         end

lib/rspec/core/example.rb

@@ -227,14 +227,14 @@ def run(example_group_instance, reporter)
               rescue Pending::SkipDeclaredInExample
                 # no-op, required metadata has already been set by the `skip`
                 # method.
-              rescue Exception => e
+              rescue NonPassthroughExceptions => e
                 set_exception(e)
               ensure
                 run_after_example
               end
             end
           end
-        rescue Exception => e
+        rescue NonPassthroughExceptions => e
           set_exception(e)
         ensure
           @example_group_instance = nil # if you love something... let it go
@@ -400,7 +400,7 @@ def hooks
 
       def with_around_example_hooks
         hooks.run(:around, :example, self) { yield }
-      rescue Exception => e
+      rescue NonPassthroughExceptions => e
         set_exception(e)
       end
 
@@ -457,7 +457,7 @@ def run_after_example
 
       def verify_mocks
         @example_group_instance.verify_mocks_for_rspec if mocks_need_verification?
-      rescue Exception => e
+      rescue NonPassthroughExceptions => e
         set_exception(e)
       end
 
@@ -476,7 +476,7 @@ def assign_generated_description
 
       def generate_description
         RSpec::Matchers.generated_description
-      rescue Exception => e
+      rescue NonPassthroughExceptions => e
         location_description + " (Got an error when generating description " \
           "from matcher: #{e.class}: #{e.message} -- #{e.backtrace.first})"
       end

lib/rspec/core/example_group.rb

@@ -524,7 +524,7 @@ def self.run(reporter=RSpec::Core::NullReporter)
         rescue Pending::SkipDeclaredInExample => ex
           for_filtered_examples(reporter) { |example| example.skip_with_exception(reporter, ex) }
           true
-        rescue Exception => ex
+        rescue NonPassthroughExceptions => ex
           RSpec.world.wants_to_quit = true if fail_fast?
           for_filtered_examples(reporter) { |example| example.fail_with_exception(reporter, ex) }
           false

lib/rspec/core/hooks.rb

@@ -362,7 +362,7 @@ def run(example)
       class AfterHook < Hook
         def run(example)
           example.instance_exec(example, &block)
-        rescue Exception => ex
+        rescue NonPassthroughExceptions => ex
           example.set_exception(ex)
         end
       end
@@ -371,7 +371,7 @@ def run(example)
       class AfterContextHook < Hook
         def run(example)
           example.instance_exec(example, &block)
-        rescue Exception => e
+        rescue NonPassthroughExceptions => e
           # TODO: Come up with a better solution for this.
           RSpec.configuration.reporter.message <<-EOS
 

spec/integration/subprocess_exit_spec.rb

@@ -0,0 +1,24 @@
+require 'support/aruba_support'
+
+RSpec.describe 'When an example forks and exits it the subprocess' do
+  include_context "aruba support"
+  before { clean_current_dir }
+
+  it 'prints the results only once' do
+    write_file_formatted "spec/fork_spec.rb", "
+      RSpec.describe do
+        example { exit unless fork }
+      end
+    "
+
+    # Must pipe output to a file to see double output bug.
+    # If used the `aruba_support` default of capturing the output
+    # in a StringIO, we won't see the output from the subprocess
+    # because it can't write to a StringIO in memory in the parent process.
+    run_command "spec/fork_spec.rb --out rspec.out"
+    in_current_dir do
+      finished_lines = File.read("rspec.out").lines.grep(/Finished in/)
+      expect(finished_lines.count).to eq(1)
+    end
+  end
+end