Strict Mode for Missing Assets

In Symfony applications you can use a JSON file manifest as the strategy to
manage asset versions. When a requested asset is not listed in manifest.json,
Symfony returns the unmodified path of the asset. This prevents the application
from breaking when some asset is missing but generates 404 errors in the browser
when trying to load the asset.

In Symfony 5.4 we’ve added a strict_mode option (which is disabled by default).
When it’s true, the application triggers an exception for missing assets, so you
can solve the issue. That’s why it’s recommended to use ‚%kernel.debug%‘ as
its value, so the application breaks in dev/test but keeps working in production:

Copy File Paths in Error Pages

The file paths of error traces in exception pages are clickable. If you configure
the framework.ide option properly, you can open those files directly on PhpStorm,
VS Code, SublimeText, etc. In Symfony 5.4 we’ve improved this page a bit more so
you can copy those file paths to clipboard. You only need to move your mouse over
some row and you’ll see a new clipboard icon to click on it:

Allow to Exclude Directories from Yaml Linting

The lint:yaml command is a nice little tool used for example to
find errors in translation files. However, sometimes you might have YAML
files which use a custom syntax extensions or advanced features not supported by
the YAML linter. In those cases, use the new –exclude option to not lint
the files included in the given directories:

New Nil ULID Class

The Uid component provides utilities to work with UUIDs and ULIDs. The UUID
standard defines a NilUuid object to represent null UUID values and
Symfony component implements it. However, even if the ULID standard doesn’t
define a NilUlid object, in Symfony 5.4 we’ve decided to add it so you can
easily create and check for null ULID values:

New String Functions

The String component provides an object-oriented API for strings and deals
with bytes, UTF-8 code points and grapheme clusters in a unified way.

In Symfony 5.4 we’ve added two new functions to it: