Data::Resolver tricky test


I hope a new test for Data::Resolver will be successful.

In Data::Resolver refactoring I digressed about re-implementing some interface functions in terms of the new underlying class Data::Resolver::Asset.

One thing that came out during the implementation was that the file() implementation - where you might want to get hold of a file - might actually have one additional requirement about persistence after exiting the process.

Up to some time ago, we would only get back a temporary file that would disappear after the process goes away. This is some kind of minimum viable product, because the recipient of this file might always produce a copy and get a persistent representation.

On the other hand, it was something useful so I decided to go for it.

To test it, the best think I could figure out is to fork() to a child process that calls the file() method, then check in the parent process whether the deletion (or lack thereof) is successful. It’s a long time I don’t play with fork(), so I hope I got it right:

sub forked_data_to_file ($data, $keep) {
   pipe my $rfh, my $wfh or die "pipe(): $!";
   my $pid = fork() // die "fork(): $!";
   if ($pid) { # parent process
      close $wfh;
      my ($filename) = <$rfh>;
      close $rfh;
      return $filename;
   else {
      close $rfh;
      my $path = data_to_file($data, $keep);
      print {$wfh} $path;
      close $wfh;
      exit 0;

Before spawning the child process, we create a pair of connected sockets, one for reading and one for writing. This will allow the child process to do the file() magic and pass the name of the generated file back to the parent.

I’m a bit worried about releasing this test, especially regarding Windows where I know that fork() is not a prime-class citizen.

Additionally, I’m not even sure I’m getting the close() and wait() order right. Or if I’m missing anything. A few tests on my VM seem to be fine, but… they’re a few tests on my VM.

I’ll eventually bite the bullet and do a trial release, anyway.

Stay safe!

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