Custom environments in subinterpreters

Feature or enhancement

Proposal:

I wanted to explore the viability of having custom environments in subinterpreters. There are several use-cases that could be enabled by this feature.

So far, from informal discussion with others about this, there are a couple possible issues to take into consideration.

Issues

1. Some of the immortal objects shared between subinterpreter may be environment-dependent (pointed out by @Yhg1s)
2. Complications around dynamic loading, by having extension modules from different environments
   2.1) Symbol conflicts from their dependencies (pointed out by @Yhg1s)
   2.2) Since subinterpreters share the same process, when loading the same shared object, they get the same pointer (pointed out by @pablogsal)

Implementation

The main thing we need is a way to disable the site initialization, which could be a enable_site option in the interpreter config. This should disable the environment customizations, and result in a bare environment without anything extra sys.path.

However, to make the use of different environments more ergonomic, we could add an environment_path location pointing to a directory containing a pyvenv.cfg, which would perform the site initialization for that environment.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

この issue ではファイルもテストも指定されていないため、まず subinterpreter のインタープリター設定と site の初期化を確認してください。提案されている enable_site と environment_path のオプションについて、列挙されている immortal-object と dynamic-loading に関する懸念を踏まえて評価してください。これらの懸念を解消し、実装範囲を定義する合意済みの設計ができた時点で完了とします。