[GR-20046] Implement exception option for Kernel#system.

PullRequest: truffleruby/1255

Author: bjfish

CHANGELOG.md

@@ -97,6 +97,7 @@ Compatibility:
 * Implemented `rb_module_new`, `rb_define_class_id`, `rb_define_module_id`, (#1876, @chrisseaton).
 * Implemented `ENV.slice`.
 * Support for the Darkfish theme for RDoc generation has been added back.
+* Implemented `Kernel#system` `exception: true` option.
 
 Performance:
 

spec/tags/core/kernel/system_tags.txt

@@ -16,7 +16,7 @@ slow:Kernel.system executes with `sh` if the command contains shell characters
 slow:Kernel.system ignores SHELL env var and always uses `sh`
 slow:Kernel.system expands shell variables when given a single string argument
 slow:Kernel.system does not expand shell variables when given multiples arguments
-fails:Kernel#system raises RuntimeError when `exception: true` is given and the command exits with a non-zero exit status
-fails:Kernel#system raises Errno::ENOENT when `exception: true` is given and the specified command does not exist
-fails:Kernel.system raises RuntimeError when `exception: true` is given and the command exits with a non-zero exit status
-fails:Kernel.system raises Errno::ENOENT when `exception: true` is given and the specified command does not exist
+slow:Kernel#system raises RuntimeError when `exception: true` is given and the command exits with a non-zero exit status
+slow:Kernel#system raises Errno::ENOENT when `exception: true` is given and the specified command does not exist
+slow:Kernel.system raises RuntimeError when `exception: true` is given and the command exits with a non-zero exit status
+slow:Kernel.system raises Errno::ENOENT when `exception: true` is given and the specified command does not exist

src/main/ruby/truffleruby/core/kernel.rb

@@ -505,14 +505,30 @@ def syscall(*args)
   module_function :syscall
 
   def system(*args)
+    options = Truffle::Type.try_convert(args.last, Hash, :to_hash)
+    exception = if options
+                  args[-1] = options
+                  options.delete(:exception)
+                else
+                  false
+                end
+
     begin
       pid = Process.spawn(*args)
-    rescue SystemCallError
+    rescue SystemCallError => e
+      raise e if exception
       return nil
     end
 
     Process.waitpid pid
-    $?.exitstatus == 0
+    result = $?.exitstatus == 0
+    return true if result
+    if exception
+      # TODO  (bjfish, 9 Jan 2020): refactoring needed for more descriptive errors
+      raise RuntimeError, 'command failed'
+    else
+      return false
+    end
   end
   module_function :system