Installation breaks when Homebrew upgrades Python due to dangling dylib reference

[cjolowicz]

• I am on the latest Poetry version.
• I have searched the issues of this repo and believe that this is not a duplicate.

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• OS version and name: macOS 12.5.1 (Intel)
• Poetry version: 1.2.0
• Python version: 3.10.6_2 (Homebrew)

The Poetry installation breaks when Homebrew upgrades Python to a new maintenance release or to a new downstream release (e.g. 3.10.6_1 to 3.10.6_2). The error message is the following:

dyld[8108]: Library not loaded: '/usr/local/Cellar/python@3.10/3.10.6_1/Frameworks/Python.framework/Versions/3.10/Python'
  Referenced from: '/Users/user/Library/Application Support/pypoetry/venv/bin/python'
  Reason: tried: '/usr/local/Cellar/python@3.10/3.10.6_1/Frameworks/Python.framework/Versions/3.10/Python' (no such file), '/Library/Frameworks/Python.framework/Versions/3.10/Python' (no such file), '/System/Library/Frameworks/Python.framework/Versions/3.10/Python' (no such file)

You should be able to reproduce this by:

1. Install an older version of the main Homebrew Python (python@3), e.g. 3.10.6_1
2. Install Poetry using the default method
3. Upgrade the main Homebrew Python
4. Invoke Poetry

The problem appears to be that the installer creates the virtual environment with copies instead of symlinks. This is a good default for Windows, but not for macOS. On macOS, the copied interpreter binary references the Python dynamic library using a path including the full version number. When Homebrew upgrades Python, this path disappears. By contrast, virtual environments created with the default strategy use a symbolic link that remains stable for all releases of a Python feature version (major.minor). Upgrading Python to a maintenance release seamlessly and implicitly upgrades any associated virtual environments.

The problem is here:

            builder = venv.EnvBuilder(clear=True, with_pip=True, symlinks=False)

I suggest omitting the symlink argument and using the platform default instead, which is False on Windows and True elsewhere.

[neersighted]

Duplicate #24