In a "wait" method of Symfony\Component\Process\Process class (in combination of "updateStatus" method), what happens is that

• pipes get read
• process status gets updated
  until process gets marked as closed when
• pipes get closed
• process gets closed

I noticed that sometimes in this loop or pipes read and process update what occurs is this. Pipes don't get read yet cause output was not generated. Not sure if just after pipe reading or just before process update, process finishes, Process component detects process closed and goes on to process closing.

This is what keeps happening with NodeJs implementation of Less assetic filter on Windows with a lot of people (where temp files are used instead of pipes). Personally didn't have problem with this for a long time with this, and then suddenly my css files came out empty. Reading pipes in "wait" method just before calling "close" method gets output read correctly.