Make --bisect work in SPEC_OPTS

Proof-of-concept - not intended for merge!

Previously, using SPEC_OPTS='--bisect' would result in infinite rspec
processes starting, as every child process spawned by bisect would still have
"--bisect" in the ENV, and would start the bisection anew.

While Open3.capture2e accepts an environment value, this is merged with the
parent process's ENV to give the new process its environment, so we can't just
delete 'SPEC_OPTS' from the env, we need to overwrite it with a blank value:

    Open3.capture2e({ 'SPEC_OPTS' => '' }, cmd)

This resolves resolved the infinite process problem, but highlighted a new
problem.

Due to the way the Bisect::Runner is invoked in options parsing, the bisection
lost any options specified at the command line. For example:

    $ SPEC_OPTS='--bisect' rspec blah_spec.rb --seed 1234

Because SPEC_OPTS and ARGV are parsed separately, in this case
`#bisect_and_exit` gets invoked during the parsing of SPEC_OPTS, which means
that the bisect runner is started without the file and seed arguments.

To address this I've made the OptionParser set a :bisect option, which is then
picked up in the main Runner to invoke the actual bisection. I've also had to
bodge in a means of getting the combined CLI and environment args to pass to
the Bisect::Runner. This is why we need to completely clear SPEC_OPTS for the
child processes, rather than just remove "--bisect", as all the args passed in
the parent's SPEC_OPTS get moved to the CLI args for the child command.

The bisect tests fail on this commit because of the aruba helpers modifying
the SPEC_OPTS environment variable, which affects the test output. The bisect
feature itself does now work with SPEC_OPTS='--bisect', however.

Author: urbanautomaton

lib/rspec/core/bisect/runner.rb

@@ -71,14 +71,14 @@ def run_locations(*capture_args)
         # https://github.com/jruby/jruby/issues/2766
         if Open3.respond_to?(:capture2e) && !RSpec::Support::Ruby.jruby?
           def run_command(cmd)
-            Open3.capture2e(cmd).first
+            Open3.capture2e(spec_opts_without_bisect, cmd).first
           end
         else # for 1.8.7
           # :nocov:
           def run_command(cmd)
             out = err = nil
 
-            Open3.popen3(cmd) do |_, stdout, stderr|
+            Open3.popen3(spec_opts_without_bisect, cmd) do |_, stdout, stderr|
               # Reading the streams blocks until the process is complete
               out = stdout.read
               err = stderr.read
@@ -89,6 +89,10 @@ def run_command(cmd)
           # :nocov:
         end
 
+        def spec_opts_without_bisect
+          { 'SPEC_OPTS' => ENV.fetch('SPEC_OPTS', '').gsub(/--bisect/, '') }
+        end
+
         def reusable_cli_options
           @reusable_cli_options ||= begin
             opts = original_cli_args_without_locations

lib/rspec/core/option_parser.rb

@@ -68,7 +68,7 @@ def parser(options)
 
         parser.on('--bisect[=verbose]', 'Repeatedly runs the suite in order to isolate the failures to the ',
                   '  smallest reproducible case.') do |argument|
-          bisect_and_exit(argument)
+          options[:bisect] = argument || true
         end
 
         parser.on('--[no-]fail-fast[=COUNT]', 'Abort the run after a certain number of failures (1 by default).') do |argument|
@@ -288,23 +288,6 @@ def initialize_project_and_exit
       exit
     end
 
-    def bisect_and_exit(argument)
-      RSpec::Support.require_rspec_core "bisect/coordinator"
-
-      success = Bisect::Coordinator.bisect_with(
-        original_args,
-        RSpec.configuration,
-        bisect_formatter_for(argument)
-      )
-
-      exit(success ? 0 : 1)
-    end
-
-    def bisect_formatter_for(argument)
-      return Formatters::BisectDebugFormatter if argument == "verbose"
-      Formatters::BisectProgressFormatter
-    end
-
     def print_version_and_exit
       puts RSpec::Core::Version::STRING
       exit

lib/rspec/core/runner.rb

@@ -73,11 +73,30 @@ def self.run(args, err=$stderr, out=$stdout)
           rescue DRb::DRbConnError
             err.puts "No DRb server is running. Running in local process instead ..."
           end
+        elsif options.options[:bisect]
+          bisect_and_exit(options.options[:bisect], args)
         end
 
         new(options).run(err, out)
       end
 
+      def self.bisect_and_exit(argument, original_args)
+        RSpec::Support.require_rspec_core "bisect/coordinator"
+
+        success = Bisect::Coordinator.bisect_with(
+          original_args,
+          RSpec.configuration,
+          bisect_formatter_for(argument)
+        )
+
+        exit(success ? 0 : 1)
+      end
+
+      def self.bisect_formatter_for(argument)
+        return Formatters::BisectDebugFormatter if argument == "verbose"
+        Formatters::BisectProgressFormatter
+      end
+
       def initialize(options, configuration=RSpec.configuration, world=RSpec.world)
         @options       = options
         @configuration = configuration