config_parser: prevent trailing whitespace in output (string → word) (#5117)

fixes https://github.com/i3/i3/issues/5064

parser-specs/config.spec

@@ -565,7 +565,7 @@ state BAR_POSITION:
       -> call cfg_bar_position($position); BAR
 
 state BAR_OUTPUT:
-  output = string
+  output = word
       -> call cfg_bar_output($output); BAR
 
 state BAR_TRAY_OUTPUT:

testcases/t/317-bar-output-trailing-space.t

@@ -0,0 +1,71 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • https://build.i3wm.org/docs/testsuite.html
+#   (or docs/testsuite)
+#
+# • https://build.i3wm.org/docs/lib-i3test.html
+#   (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • https://build.i3wm.org/docs/ipc.html
+#   (or docs/ipc)
+#
+# • http://onyxneon.com/books/modern_perl/modern_perl_a4.pdf
+#   (unless you are already familiar with Perl)
+#
+# Verifies that any trailing whitespace in strings (including in
+# “bar { output <output> }” in particular) is stripped.
+# Ticket: #5064
+# Bug still in: 4.20-105-g4db383e4
+use i3test i3_autostart => 0;
+
+# Test with a single output.
+
+my $config = <<EOT;
+# i3 config file (v4)
+font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
+
+bar {
+  output anything 
+}
+EOT
+
+my $pid = launch_with_config($config);
+
+my $i3 = i3(get_socket_path(0));
+my $bars = $i3->get_bar_config()->recv;
+is(@$bars, 1, 'one bar configured');
+my $bar_id = shift @$bars;
+
+my $bar_config = $i3->get_bar_config($bar_id)->recv;
+is_deeply($bar_config->{outputs}, [ 'anything' ], 'outputs do not have trailing whitespace');
+
+exit_gracefully($pid);
+
+# Test with multiple outputs for a single bar.
+
+$config = <<EOT;
+# i3 config file (v4)
+font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
+
+bar {
+  output nospace
+  output singlespace 
+}
+EOT
+
+$pid = launch_with_config($config);
+
+$i3 = i3(get_socket_path(0));
+$bars = $i3->get_bar_config()->recv;
+is(@$bars, 1, 'one bar configured');
+$bar_id = shift @$bars;
+
+$bar_config = $i3->get_bar_config($bar_id)->recv;
+is_deeply($bar_config->{outputs}, [ 'nospace', 'singlespace' ], 'outputs do not have trailing whitespace');
+
+exit_gracefully($pid);
+
+
+done_testing;