Yii2: Integrate `yiisoft/di`

[klimov-paul]

DI container from yiisoft/di should be integrated into main repo replacing old DI classes before 2.1 release.
The location and internal code of the following classes should be rewised:

• yii\di\Instance
• yii\di\ServiceLocator

Keep in mind that namespace yii\di is taken by yiisoft/di package. While Composer allows having multiple folders for the same namespace, I would like to avoid such approach as it will make code navigation difficult.

PR for 'class' keyword fallback should be considered to be handled at yiisoft/yii instead of yiisoft/di. If there will be a graceful way to provide fallback from __class to class it could be done - if not - no fallback will be provided.

[samdark]

I think we can use it via composer instead of getting it into repository directly.

[klimov-paul]

Obviously.

[samdark]

We don't need Instance since there's https://github.com/yiisoft/di/blob/master/src/Reference.php

[samdark]

ServiceLocator could be moved to base.

[samdark]

Another thing is that yiisoft/di doesn't have built-in support for factories (should not be container job, I think) that we use for widgets.

[klimov-paul]

We don't need Instance since there's Reference

What about Instance::ensure() then? It is widely used around the Yii code.

[samdark]

Yes. That's missing.

[klimov-paul]

Intermediate changeset applied, allowing usage of '__class' keyword for definitions:
b04e0e06dc0939ae0b3c822656f1114f76ee320f
d1ff652b2f0baabbfb9e8776659167508eff5632

Thus the entire code will not break after "yiisoft/di" integration.

[SilverFire]

I'd suggest to implement __construct() parameter support as well.

1. It is consistent with config format agreed for yiisoft/di
2. While yiisoft/di is a bit raw and not integrated in Yii 2.1, this change will help us to write configs that will work after yiisoft/di adoption.

[hiqsol]

Please, consider reopening: #15815

[schmunk42]

Will this be PSR-11 compatible?

[samdark]

Yes, yiisoft/di is PSR-11 compatible.

[samdark]

After several attempts to integrate yiisoft/di by me, @SilverFire and @hiqsol which took too much time and weren't really successful decided not to do it. Instead:

• [ ] Declare an interface for DI container in yiisoft/yii2. Make it an extension of PSR if possible.
• [ ] Port cycles in dependencies detection from yiisoft/di.
• [ ] Port method calls support from yiisoft/di.
• [ ] Remove ability to set constructor options from method signatures, move it to __construct.

It's all indicated in roadmap so closing this issue.