testsuite: eliminate sleep, wait until i3 replies via IPC

testcases/complete-run.pl

@@ -29,6 +29,18 @@ use Try::Tiny;
 use Getopt::Long;
 use Time::HiRes qw(sleep);
 use X11::XCB::Connection;
+use IO::Socket::UNIX; # core
+use POSIX; # core
+use AnyEvent::Handle;
+
+# open a file so that we get file descriptor 3. we will later close it in the
+# child and dup() the listening socket file descriptor to 3 to pass it to i3
+open(my $reserved, '<', '/dev/null');
+if (fileno($reserved) != 3) {
+    warn "Socket file descriptor is not 3.";
+    warn "Please don't start this script within a subshell of vim or something.";
+    exit 1;
+}
 
 # install a dummy CHLD handler to overwrite the CHLD handler of AnyEvent / EV
 # XXX: we could maybe also use a different loop than the default loop in EV?
@@ -72,7 +84,6 @@ for my $display (@displays) {
     };
 }
 
-my $i3cmd = abs_path("../i3") . " -V -d all --disable-signalhandler";
 my $config = slurp('i3-test.config');
 
 # 1: get a list of all testcases
@@ -116,21 +127,90 @@ take_job($_) for @wdisplays;
 #
 sub take_job {
     my ($display) = @_;
+
+    my $test = shift @testfiles;
+    return unless $test;
+    my $dont_start = (slurp($test) =~ /# !NO_I3_INSTANCE!/);
+    my $logpath = "$outdir/i3-log-for-" . basename($test);
+
     my ($fh, $tmpfile) = tempfile();
     say $fh $config;
     say $fh "ipc-socket /tmp/nested-$display";
     close($fh);
 
-    my $test = shift @testfiles;
+    my $activate_cv = AnyEvent->condvar;
-    return unless $test;
+    my $start_i3 = sub {
-    my $logpath = "$outdir/i3-log-for-" . basename($test);
+        # remove the old unix socket
-    my $cmd = "export DISPLAY=$display; exec $i3cmd -c $tmpfile >$logpath 2>&1";
+        unlink("/tmp/nested-$display-activation");
-    my $dont_start = (slurp($test) =~ /# !NO_I3_INSTANCE!/);
 
-    my $process = Proc::Background->new($cmd) unless $dont_start;
+        # pass all file descriptors up to three to the children.
-    say "[$display] Running $test with logfile $logpath";
+        # we need to set this flag before opening the socket.
+        open(my $fdtest, '<', '/dev/null');
+        $^F = fileno($fdtest);
+        close($fdtest);
+        my $socket = IO::Socket::UNIX->new(
+            Listen => 1,
+            Local => "/tmp/nested-$display-activation",
+        );
+
+        my $pid = fork;
+        if (!defined($pid)) {
+            die "could not fork()";
+        }
+        say "pid = $pid";
+        if ($pid == 0) {
+            say "child!";
+            $ENV{LISTEN_PID} = $$;
+            $ENV{LISTEN_FDS} = 1;
+            $ENV{DISPLAY} = $display;
+            $^F = 3;
+
+            say "fileno is " . fileno($socket);
+            close($reserved);
+            POSIX::dup2(fileno($socket), 3);
+
+            # now execute i3
+            my $i3cmd = abs_path("../i3") . " -V -d all --disable-signalhandler";
+            my $cmd = "exec $i3cmd -c $tmpfile >$logpath 2>&1";
+            exec "/bin/sh", '-c', $cmd;
+
+            # if we are still here, i3 could not be found or exec failed. bail out.
+            exit 1;
+        }
+
+        my $child_watcher;
+        $child_watcher = AnyEvent->child(pid => $pid, cb => sub {
+            say "child died. pid = $pid";
+            undef $child_watcher;
+        });
+
+        # close the socket, the child process should be the only one which keeps a file
+        # descriptor on the listening socket.
+        $socket->close;
+
+        # We now connect (will succeed immediately) and send a request afterwards.
+        # As soon as the reply is there, i3 is considered ready.
+        my $cl = IO::Socket::UNIX->new(Peer => "/tmp/nested-$display-activation");
+        my $hdl;
+        $hdl = AnyEvent::Handle->new(fh => $cl, on_error => sub { $activate_cv->send(0) });
+
+        # send a get_tree message without payload
+        $hdl->push_write('i3-ipc' . pack("LL", 0, 4));
+
+        # wait for the reply
+        $hdl->push_read(chunk => 1, => sub {
+            my ($h, $line) = @_;
+            say "read something from i3";
+            $activate_cv->send(1);
+            undef $hdl;
+        });
+
+        return $pid;
+    };
+
+    my $pid;
+    $pid = $start_i3->() unless $dont_start;
 
-    sleep 0.5;
     my $kill_i3 = sub {
         # Don’t bother killing i3 when we haven’t started it
         return if $dont_start;
@@ -148,9 +228,18 @@ sub take_job {
         }
 
         say "[$display] killing i3";
-        kill(9, $process->pid) or die "could not kill i3";
+        kill(9, $pid) or die "could not kill i3";
     };
 
+    # This will be called as soon as i3 is running and answered to our
+    # IPC request
+    $activate_cv->cb(sub {
+        say "cb";
+        my ($status) = $activate_cv->recv;
+        say "complete-run: status = $status";
+
+        say "[$display] Running $test with logfile $logpath";
+
         my $output;
         my $parser = TAP::Parser->new({
             exec => [ 'sh', '-c', "DISPLAY=$display /usr/bin/perl -It/lib $test" ],
@@ -195,6 +284,9 @@ sub take_job {
             );
             push @watchers, $w;
         }
+    });
+
+    $activate_cv->send(1) if $dont_start;
 }
 
 $cv->recv;