Rule declare_strict_types does not work on files that start with a "hashbang" line

[krzysztof-sikorski]

Bug report

Description

The rule declare_strict_types does not work on files that start with a "hashbang" line:

#!/usr/bin/env php
<?php
// the rest of the file

I discovered the bug when I tried to reformat a bin/console file generated by Symfony CLI,
but further testing soon revealed that the rule simply ignores "mixed content" files
that contain any non-PHP lines before the <php opening tag.

While I understand that the behaviour might be intentional (to avoid corrupting files
where the declare statement would have no effect or wrong effect), I also think that
the hashbang line should be an exception and files that start with it but contain no other
non-PHP content should be treated as "pure PHP" files and modified by the rule.

Runtime version

PHP CS Fixer 3.43.0 Three Keys by Fabien Potencier and Dariusz Ruminski.
PHP runtime: 8.3.1

Used command

vendor/bin/php-cs-fixer -vvv fix

Configuration file

<?php
$rules = [
    'declare_strict_types' => true,
];

$finder = new PhpCsFixer\Finder();
$finder->in(__DIR__);

$config = new PhpCsFixer\Config();
$config->setRiskyAllowed(true);
$config->setRules($rules);
$config->setFinder($finder);

return $config;

Code snippet that reproduces the problem

#!/usr/bin/env php
<?php
echo 'PHP-CS-Fixer should add declare statement above!';

Expected result:

#!/usr/bin/env php
<?php declare(strict_types=1);
echo 'PHP-CS-Fixer should add declare statement above!';

Actual result: file is not changed at all.

Here is a simple repository that demonstrates the bug:
https://github.com/krzysztof-sikorski/php-cs-fixer-declare-strict-types-bug

Just pull the code, execute composer install, and then vendor/bin/php-cs-fixer -vvv fix.

[keradus]

potential testcase:

diff --git a/tests/Fixer/Strict/DeclareStrictTypesFixerTest.php b/tests/Fixer/Strict/DeclareStrictTypesFixerTest.php
index 709d50456..f42e138a6 100644
--- a/tests/Fixer/Strict/DeclareStrictTypesFixerTest.php
+++ b/tests/Fixer/Strict/DeclareStrictTypesFixerTest.php
@@ -130,6 +130,15 @@ class A {
             '<?php declare(strict_types=0);',
         ];
 
+        yield [
+            "#!/usr/bin/env php
+<?php declare(strict_types=1);
+echo 'foo';",
+            "#!/usr/bin/env php
+<?php
+echo 'foo';",
+        ];

• class to handle the fix: DeclareStrictTypesFixer
• potential helper to use: $tokens->isMonolithicPhp(), that is already checking for shebang

@krzysztof-sikorski , would you like to give it a try?

[keradus]

promoting to feature due to https://github.com/PHP-CS-Fixer/PHP-CS-Fixer/blob/master/feature-or-bug.rst

[krzysztof-sikorski]

@keradus I'm not sure if I fully understand the project's architecture but yes, I am willing to try.

Because this issue got classified as a feature instead of bug, then maybe the new behaviour should be configurable and disabled by default, to keep backward compatibility?

[keradus]

Thanks!

I'm open to have it behind config