lesser-evil / shell-verbosity-is-evil
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Last update: 2024-10-30 01:59:42 UTC
README
The SHELL_VERBOSITY
environment variable was introduced in symfony/console
3.4 and still appears in symfony/console
6.2. It defines a gooey,
sticky form of verbosity.
The theory seems to be: if you call a command in verbose mode (-v
), and if it calls any subcommands, then all those subcommands should also run in
verbose mode. I suppose this is OK if the various commands follow simple, sequential procedures with outputs shown to a human.
But this convention is actively harmful when programs are composed in Unix-style. For simplicity, consider a Symfony Console command (snafu
)
which invokes a subcommand:
class SnafuCommand extends Command { public function execute(...) { shell_exec('find_data | filter_data > /tmp/my_data.json'); $data = json_decode(file_get_contents('/tmp/my_data.json')); } }
If you call snafu -v
, then Symfony surrepetitiously sets SHELL_VERBOSITY=1
and propagates it to each subprocess. So filter_data
receives
SHELL_VERBOSITY=1
and begins outputting a processing log -- in addition to its regular JSON output. Now, the file /tmp/my_data.json
is no longer
JSON -- it is JSON plus random noise. So anything reading my_data.json
will break.
The overall effect is to make the system flaky. Any Symfony-based command can cause this problem (by setting SHELL_VERBOSITY
) or become broken by
it (by accepting SHELL_VERBOSITY
). If something breaks, you have to trawl the process-graph to find the two parties to the breakage. The breakage
only happens when running snafu -v
. If you run commands individually, or if you run snafu
normally, then it works -- which will confound
debugging efforts.
Of course, the reason to use -v
is to debug something. If -v
itself causes another bug, then you're investigating the combined behavior of two bugs.
How to remove SHELL_VERBOSITY
Friends don't let friends use SHELL_VERBOSITY
. This repo defines an adapter to kill SHELL_VERBOSITY
.
composer require lesser-evil/shell-verbosity-is-evil
In Symfony 3.4 - 6.2, the SHELL_VERBOSITY
behavior is defined by Application::configureIO()
. Override this:
use LesserEvil\ShellVerbosityIsEvil; class MyApplication extends Application { protected function configureIO(InputInterface $input, OutputInterface $output) { ShellVerbosityIsEvil::doWithoutEvil(function() use ($input, $output) { parent::configureIO($input, $output); }); } }