feature #28449 [DependencyInjection] improved message when alias service is not found (xabbuh)
feature #28449 [DependencyInjection] improved message when alias service is not found (xabbuh)

This PR was merged into the 4.2-dev branch.

Discussion
----------

[DependencyInjection] improved message when alias service is not found

| Q             | A
| ------------- | ---
| Branch?       | 2.8
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #28413
| License       | MIT
| Doc PR        |

When using the YAML config format, it can be confusing that you need to
prefix the aliased service id with an `@` character when passing it as
a string, but that you have to omit it when using the `alias` attribute:

```yaml
foo: '@App\Foo'

foo:
    alias: 'App\Foo'
```

This commit will enhance the generated error message in cases where the
aliased service id is prefixed with the `@` character in the `alias`
option like this:

```yaml
foo:
    alias: '@App\Foo'
```

Commits
-------

280ecbc2be improved message when alias service is not found

symfony/DependencyInjection,symfony/dependency-injection