I don't know if we should make this change (at the moment we're doing the opposite in other parts of the framework: stop being case-insensitive) but I can confirm that this is a very annoying issue. I make this error almost every day. In my case the error is: server:Start instead of server:start 😡

I agree being strict is perfect for bots and automated stuff. Bots will/should not use shortcuts though. This is purely good for DX that I believe is very important. I don't believe it should be in the same bucket as other more restrictive flows

👍 for this idea, even if I've never hit such an issue myself.

This is a BC break. Taking the same example as in your test case:

// test.php
$app = new Symfony\Component\Console\Application();
$app->register('FOO:BAR')->setCode(function () { print 'FOO:BAR executed'; });
$app->register('foo:bar')->setCode(function () { print 'foo:bar executed'; });
$app->run();

Current behavior is:

$ php test.php F:B
FOO:BAR executed

$ php test.php f:b
foo:bar executed

With this, both f:b and F:B become ambiguous and no one runs, so 👎 for this PR as is.

If we want to fix this issue, we should make command names case insensitive (as @javiereguiluz seems to be asking for), not only shortcuts, and that would require a proper upgrade path.
I'm not opposed to that idea either, but I wonder if we are not missing some valid use cases for case-sensitive command names.

@chalasr I agree this is a BC break as you stated it. I've updated the table to mark it as such.
This will break functionality for people explicitly choosing to use case sensitive shortcuts by matching more than one commands (not choosing an unexpected one) and refusing to run.
Therefore it would require either more characters to match uniquely or the full command for precision.

But if we assume that such a person exists that prefers f:b, f:B and F:B to match different things, for them I would say having to type : is an even bigger problem. Or they've never noticed that they've been running the wrong command. I would say allowing f:b and f:B pointing to different commands is already bad as too error prone.

I do like the idea of having all commands case insensitive. That would also solve the problem but I don't know how much work that is.

There was a nice talk by @ellotheth called Building for Utopia at PHPTek talking about similar issues.

@nicolas-grekas I think we can. I will try that

Ready for review again.

Could you add a note in the Console CHANGELOG?

Thanks @chalasr I've updated the Console CHANGELOG

Thank you for contributing to Symfony @thanosp.