PHPStan should not crash on startup when projects' composer.json is invalid

[staabm]

instead of trusting data we got back from json-decoding composer.json, we now verify it and skip processing data which does not adhere to the types we expect to prevent crashing down the line.

closes phpstan/phpstan#14724

[VincentLanglet]

What's the output then ? Should we still have an error message ?

[staabm]

the "output" is a regular PHPStan result which ignored settings from composer.json.
we ignore other composer errors in a similar way already before this PR.

such a invalid composer.json will already be warned about when running "composer update" or similar.

[phpstan-bot]

This pull request has been marked as ready for review.

[talkinnl]

the "output" is a regular PHPStan result which ignored settings from composer.json. we ignore other composer errors in a similar way already before this PR.

such a invalid composer.json will already be warned about when running "composer update" or similar.

I see how you apply existing behavior, but that behavior does sound like a bug.

If composer.json is in a bad shape, all bets are off. Better to fail fast and loud.

[staabm]

@talkinnl if you see room for improvement, feel free to contribute