Pants tests induce PEXWarning from resolve package collisions

[cburroughs]

Describe the bug
Several examples along the lines of:

$ pants test src/python/pants/backend/python/packaging::
16:38:01.66 [INFO] Canceled: Building 8 requirements for requirements.pex from the 3rdparty/python/user_reqs.lock resolve: PyYAML<7.0,>=6.0, ansicolors==1.1.8, packaging==21.3, pytest<7.1.0,>=6.2.4, toml==0.10.2, types-PyYAML==6.... (49 characters truncated)
16:38:01.66 [INFO] Canceled: Building 8 requirements for requirements.pex from the 3rdparty/python/user_reqs.lock resolve: PyYAML<7.0,>=6.0, ansicolors==1.1.8, packaging==21.3, pytest<7.1.0,>=6.2.4, toml==0.10.2, types-PyYAML==6.... (49 characters truncated)
16:38:06.59 [INFO] Completed: Building 8 requirements for requirements.pex from the 3rdparty/python/user_reqs.lock resolve: PyYAML<7.0,>=6.0, ansicolors==1.1.8, packaging==21.3, pytest<7.1.0,>=6.2.4, toml==0.10.2, types-PyYAML==6.... (49 characters truncated)
16:38:07.68 [INFO] Completed: Building 18 requirements for requirements.pex from the 3rdparty/python/user_reqs.lock resolve: PyYAML<7.0,>=6.0, ansicolors==1.1.8, chevron==0.14.0, fasteners==0.16.3, ijson==3.1.4, node-semver==0.9.0... (247 characters truncated)
16:38:22.19 [INFO] Completed: Building 8 requirements for pytest.pex from the 3rdparty/python/pytest.lock resolve: ipdb, pygments, pytest-asyncio, pytest-cov!=2.12.1,<3.1,>=2.12, pytest-html, pytest-icdiff, pytest-xdist<3,>=2.5, p... (12 characters truncated)
16:38:23.49 [INFO] Completed: Building local_dists.pex
16:38:26.06 [INFO] Completed: Building pytest_runner.pex
16:38:26.06 [INFO] Completed: Building pytest_runner.pex
16:38:26.06 [WARN] /home/ecsb/.cache/pants/named_caches/pex_root/installed_wheels/7309da7faa3a99f960f878ee917815b3ceb40d69205b7d496d88faa5a8c4db76/pex-2.2.1-py2.py3-none-any.whl/pex/venv/installer.py:241: PEXWarning: Encountered collision populating /home/ecsb/.cache/pants/named_caches/pex_root/venvs/s/ffd73ab4/venv from PEX at pytest_runner.pex:
1. /home/ecsb/.cache/pants/named_caches/pex_root/venvs/d065c874c21c7a9cb6712591555c1b3a1475c9a6/36cca69703bf5917ad2fd12b1106f113b4efab88.lck.work/lib/python3.9/site-packages/typing_extensions.py was provided by:
	sha1:cfffc86f5e733ca91918bf905055735e159e200b -> /home/ecsb/.cache/pants/named_caches/pex_root/installed_wheels/aa26eb5b539c4e40fcb8a6f653c831d5a28c3443ba97da65ecb041d895c94382/typing_extensions-4.5.0-py3-none-any.whl/typing_extensions.py
	sha1:71f254a5a97d97ba0cd5a3ff1e73cbb8f0b27166 -> /home/ecsb/.cache/pants/named_caches/pex_root/installed_wheels/25642c956049920a5aa49edcdd6ab1e06d7e5d467fc00e0506c44ac86fbfca02/typing_extensions-4.3.0-py3-none-any.whl/typing_extensions.py
  pex_warnings.warn(message)

16:38:26.06 [WARN] /home/ecsb/.cache/pants/named_caches/pex_root/installed_wheels/7309da7faa3a99f960f878ee917815b3ceb40d69205b7d496d88faa5a8c4db76/pex-2.2.1-py2.py3-none-any.whl/pex/venv/installer.py:241: PEXWarning: Encountered collision populating /home/ecsb/.cache/pants/named_caches/pex_root/venvs/s/52ab0681/venv from PEX at pytest_runner.pex:
1. /home/ecsb/.cache/pants/named_caches/pex_root/venvs/d065c874c21c7a9cb6712591555c1b3a1475c9a6/1ac9e793bdab269adcc386c5e35a6e179b109ade.lck.work/lib/python3.9/site-packages/typing_extensions.py was provided by:
	sha1:cfffc86f5e733ca91918bf905055735e159e200b -> /home/ecsb/.cache/pants/named_caches/pex_root/installed_wheels/aa26eb5b539c4e40fcb8a6f653c831d5a28c3443ba97da65ecb041d895c94382/typing_extensions-4.5.0-py3-none-any.whl/typing_extensions.py
	sha1:71f254a5a97d97ba0cd5a3ff1e73cbb8f0b27166 -> /home/ecsb/.cache/pants/named_caches/pex_root/installed_wheels/25642c956049920a5aa49edcdd6ab1e06d7e5d467fc00e0506c44ac86fbfca02/typing_extensions-4.3.0-py3-none-any.whl/typing_extensions.py
  pex_warnings.warn(message)

That is we have one version of typing_extensions in pytest.lock and a different version in (for example) user_reqs.lock. "Normally" lockfiles are disjoint, but in the case of tools they are sometimes munged together.

I'm not sure exactly what -- if anything -- should be done here. Or rather what the recommendation should be for Pants users in the same situation short of #9206

Pants version
2d1ffe9

OS
Are you encountering the bug on MacOS, Linux, or both?

Additional info
See also #20577

[huonw]

Good catch!

I would think it'd be good not to ship this and #20577 in a stable release, potentially we should have the new option default to False for 2.20.x (and adjust the docs to indicate that there's a few "spurious" issues)?

This would relieve the pressure of needing to land potentially-broad changes to fix the underlying issues (which we presumably should fix) to unblock 2.20.0.

Thoughts?

[huonw]

(Chucked up #20590 with that idea, in case we want to go with it.)

[cburroughs]

A default of False in 2.20 and then True in 2.21 to de-risk 2.20 makes sense to me.

Pants is already pretty chatty so I do lean towards True in 2.21 even if every single case isn't squashed. This issue with typing_extensions is "probably fine" and could trivially be worked around by futzing with the pants internal lockfiles, but the same warning could be telling a user something closer "Your code is broken!" and I don't like swallowing the underlying tool trying to tell them that.

[cburroughs]

Although now that I've thought through that a little more, we probably should keep it enabled for Pants itself (in pants.toml) so we keep surfacing new cases as dogfood.

[huonw]

Removing this from the 2.20.x milestone, since we landed #20593 as a stop-gap to reduce severity in 2.20.0