`module IsolatedRubyContext`

Evaluates Ruby in a fresh process and returns its result through Marshal.

Nested Classes and Modules

class Error: Raised when the child process exits unsuccessfully without returning an exception.

Definitions

`def isolated_ruby(source, chdir: Dir.pwd, env: {}, requires: [])`

Evaluate source using the current Ruby interpreter, without sharing Ruby state or changing the caller's working directory. The final expression is serialized with Marshal.dump and restored with Marshal.load. Printed output goes to the inherited stderr. Exceptions are marshaled back and re-raised with their original backtraces. SystemExit follows the child process's exit status.

Signature

parameter　source　String: Ruby source code to evaluate.
parameter　chdir　String: The child process's working directory.
parameter　env　Hash(String, String | Nil): Child environment overrides; nil removes a variable. The environment is inherited by default, including RUBYOPT for coverage hooks.
parameter　requires　Array(String): Features to require before evaluating source, such as bundler/setup.
returns　Object: The unmarshaled result, or nil if the child exits successfully without a result. Classes used by the result must be available in the caller.
raises　Exception: The exception raised in the child process, if it can be marshaled back.
raises　Error: If the child exits unsuccessfully without returning an exception.
raises　ArgumentError: If the result or exception uses a class unavailable in the caller.

Implementation

def isolated_ruby(source, chdir: Dir.pwd, env: {}, requires: [])
	script = <<~'RUBY'
		->(output) do
			$stdout.reopen($stderr)
			begin
				source = $stdin.read
				ARGV.each{|feature| require feature}
				result = eval(source, TOPLEVEL_BINDING, File.join(Dir.pwd, "(isolated ruby)"))
				output.write(Marshal.dump([result, nil]))
			rescue SystemExit
				raise
			rescue Exception => error
				output.write(Marshal.dump([nil, error]))
			end
		end.call($stdout.dup.binmode)
	RUBY
	
	output = IO.popen([env, RbConfig.ruby, "-e", script, "--", *requires], "r+b", chdir: chdir) do |process|
		begin
			process.write(source)
		rescue Errno::EPIPE
			# A startup failure may close stdin before accepting the source:
		end
		process.close_write
		process.read
	end
	status = $?
	raise Error.new(status) unless status.success?
	return nil if output.empty?
	
	result, error = Marshal.load(output)
	raise error if error
	result
end