[python] interpreter_constraints is not used as the default IC for user resolves.

[jsirois]

As of Pants 2.16.0.dev4 (main HEAD currently), the following configuration is needed to ensure the python-default resolve gets the repo-local default IC and not the Pants-embedded default IC:

pants/pants.toml

Lines 130 to 147 in 05b9465

	[python]
	# N.B.: When adjusting this to support new Python versions, you must update the Pants
	# `python_distrobution` targets, currently:
	# + src/python/pants:pants-packaged
	# + src/python/pants/testutil:testutil_wheel
	interpreter_constraints = [">=3.7,<3.10"]
	macos_big_sur_compatibility = true
	enable_resolves = true
	[python.resolves]
	python-default = "3rdparty/python/user_reqs.lock"
	helm-post-renderer = "src/python/pants/backend/helm/subsystems/post_renderer.lock"
	helm-k8s-parser = "src/python/pants/backend/helm/subsystems/k8s_parser.lock"
	[python.resolves_to_interpreter_constraints]
	# Without setting this explicitly, the 'python-default' resolve uses the Pants default
	# ">=3.7,<4" IC, which is incorrect and can lead to a failed lock for systems with >=3.10.
	python-default = [">=3.7,<3.10"]

This feels like a bug. If the default ICs written down by the user are not picked as the default IC for a resolve written down by a user, what is the default IC used for then?

[cognifloyd]

@benjyw Does the recent default IC deprecation resolve this?

[benjyw]

AFAICT this isn't necessary now, but the proof is in the CI run for #19065.

Note that running ./pants generate-lockfiles --resolve=python-default with that change yielded no changes at all to the lockfile, and running tests and packaging worked.

However, I'm not sure why this was ever necessary. I synced back to #17957 and the same diff worked in the same way.

[benjyw]

These lines (which are all the places I've found where resolves_to_interpreter_constraints is consulted) imply that the right thing is happening:

pants/src/python/pants/backend/python/goals/lockfile.py

Line 239 in 09d09c6

resolve, python_setup.interpreter_constraints

pants/src/python/pants/backend/python/util_rules/pex.py

Line 655 in 9d845f0

python_setup.interpreter_constraints,

pants/src/python/pants/backend/python/goals/export.py

Line 379 in cf82715

request.resolve, python_setup.interpreter_constraints

[benjyw]

@jsirois am I missing something? Do you remember what the evidence was that this was necessary?

[jsirois]

If I go back to the linked Pex 2.1.120 upgrade PR where it hit main: 505ab26

Then comment out the edit:

jsirois@Gill-Windows:~/dev/pantsbuild/pants ((505ab264f7...) *) $ git diff pants.toml
diff --git a/pants.toml b/pants.toml
index ed9942170e..dd083c5aa4 100644
--- a/pants.toml
+++ b/pants.toml
@@ -144,7 +144,7 @@ helm-k8s-parser = "src/python/pants/backend/helm/subsystems/k8s_parser.lock"
 [python.resolves_to_interpreter_constraints]
 # Without setting this explicitly, the 'python-default' resolve uses the Pants default
 # ">=3.7,<4" IC, which is incorrect and can lead to a failed lock for systems with >=3.10.
-python-default = [">=3.7,<3.10"]
+#python-default = [">=3.7,<3.10"]

 [python-infer]
 assets = true

I find:

$ ./build-support/bin/generate_all_lockfiles.sh --pex
12:46:36.73 [WARN] DEPRECATED: `pants.engine.environment.Environment` is scheduled to be removed in version 2.17.0.dev0.

Use `pants.engine.env_vars.EnvironmentVars`.
12:46:36.73 [WARN] DEPRECATED: `pants.engine.environment.EnvironmentRequest` is scheduled to be removed in version 2.17.0.dev0.

Use `pants.engine.env_vars.EnvironmentVarsRequest`.
12:46:36.74 [WARN] DEPRECATED: `pants.engine.environment.CompleteEnvironment` is scheduled to be removed in version 2.17.0.dev0.

Use `pants.engine.env_vars.CompleteEnvironmentVars`.
12:47:03.75 [INFO] Completed: Generate lockfile for python-default
12:47:03.75 [ERROR] 1 Exception encountered:

Engine traceback:
  in select
    ..
  in pants.core.goals.generate_lockfiles.generate_lockfiles_goal
    `generate-lockfiles` goal

Traceback (most recent call last):
  File "/home/jsirois/dev/pantsbuild/pants/src/python/pants/engine/internals/selectors.py", line 626, in native_engine_generator_send
    res = rule.send(arg) if err is None else rule.throw(throw or err)
  File "/home/jsirois/dev/pantsbuild/pants/src/python/pants/core/goals/generate_lockfiles.py", line 423, in generate_lockfiles_goal
    for req in all_requests
  File "/home/jsirois/dev/pantsbuild/pants/src/python/pants/engine/internals/selectors.py", line 360, in MultiGet
    return await _MultiGet(tuple(__arg0))
  File "/home/jsirois/dev/pantsbuild/pants/src/python/pants/engine/internals/selectors.py", line 167, in __await__
    result = yield self.gets
  File "/home/jsirois/dev/pantsbuild/pants/src/python/pants/engine/internals/selectors.py", line 626, in native_engine_generator_send
    res = rule.send(arg) if err is None else rule.throw(throw or err)
  File "/home/jsirois/dev/pantsbuild/pants/src/python/pants/backend/python/goals/lockfile.py", line 190, in generate_lockfile
    cache_scope=ProcessCacheScope.PER_SESSION,
  File "/home/jsirois/dev/pantsbuild/pants/src/python/pants/engine/internals/selectors.py", line 120, in __await__
    result = yield self
pants.engine.process.ProcessExecutionFailure: Process 'Generate lockfile for python-default' failed with exit code 1.
stdout:

stderr:
pid 10034 -> /home/jsirois/.cache/pants/named_caches/pex_root/venvs/0a632cc5fc321767d8f0f1a96c21966cc516ae56/e24c8aee663ef1f4e963687618d4c779b1b907f5/bin/python -sE /home/jsirois/.cache/pants/named_caches/pex_root/venvs/0a632cc5fc321767d8f0f1a96c21966cc516ae56/e24c8aee663ef1f4e963687618d4c779b1b907f5/pex --disable-pip-version-check --no-python-version-warning --exists-action a --no-input --isolated -q --cache-dir /home/jsirois/.cache/pants/named_caches/pex_root/pip_cache --log /tmp/pants-sandbox-u5Q2cY/.tmp/pex-pip-log.1yqhdtbe/pip.log download --dest /tmp/pants-sandbox-u5Q2cY/.tmp/tmpg8hvlc02/home.jsirois..pyenv.versions.3.10.11.bin.python3.10 PyYAML<7.0,>=6.0 ansicolors==1.1.8 beautifulsoup4==4.11.1 chevron==0.14.0 debugpy==1.6.0 fastapi==0.78.0 fasteners==0.16.3 freezegun==1.2.1 humbug==0.2.7 ijson==3.1.4 importlib_resources==5.0.* mypy-typing-asserts==0.1.1 packaging==21.3 pex==2.1.120 psutil==5.9.0 pydevd-pycharm==203.5419.8 pytest<7.1.0,>=6.2.4 python-gnupg==0.4.9 python-lsp-jsonrpc==1.0.0 requests[security]>=2.28.1 setproctitle==1.3.2 setuptools<64.0,>=63.1.0 starlette==0.19.1 strawberry-graphql[fastapi]==0.114.0 toml==0.10.2 types-PyYAML==6.0.3 types-freezegun==1.1.6 types-requests==2.28.1 types-setuptools==62.6.1 types-toml==0.10.8 typing-extensions==4.3.0 uvicorn[standard]==0.17.6 --index-url https://pypi.org/simple/ --retries 5 --timeout 15 exited with 1 and STDERR:
ERROR: Could not find a version that satisfies the requirement pex==2.1.120
ERROR: No matching distribution found for pex==2.1.120




Use `--keep-sandboxes=on_failure` to preserve the process chroot for inspection.


Traceback (most recent call last):
  File "/tmp/pants-sandbox-a79QM5/./.cache/pex_root/venvs/101fe39c3b8494a801d84acf4cbdcf13f391c891/d6c8637f58f115f4f4b928f4612e8865e7f6a763/pex", line 270, in <module>
    runpy.run_module(module_name, run_name="__main__", alter_sys=True)
  File "/home/jsirois/.pyenv/versions/3.7.16/lib/python3.7/runpy.py", line 205, in run_module
    return _run_module_code(code, init_globals, run_name, mod_spec)
  File "/home/jsirois/.pyenv/versions/3.7.16/lib/python3.7/runpy.py", line 96, in _run_module_code
    mod_name, mod_spec, pkg_name, script_name)
  File "/home/jsirois/.pyenv/versions/3.7.16/lib/python3.7/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/tmp/pants-sandbox-a79QM5/build-support/bin/_generate_all_lockfiles_helper.py", line 244, in <module>
    main()
  File "/tmp/pants-sandbox-a79QM5/build-support/bin/_generate_all_lockfiles_helper.py", line 233, in main
    update_internal_lockfiles(specified=["python-default"])
  File "/tmp/pants-sandbox-a79QM5/build-support/bin/_generate_all_lockfiles_helper.py", line 205, in update_internal_lockfiles
    subprocess.run(args, check=True)
  File "/home/jsirois/.pyenv/versions/3.7.16/lib/python3.7/subprocess.py", line 512, in run
    output=stdout, stderr=stderr)
subprocess.CalledProcessError: Command '['./pants', '--concurrent', "--python-interpreter-constraints=['CPython>=3.7,<4']", '--python-enable-resolves', 'generate-lockfiles', "--resolve=['python-default']"]' returned non-zero exit status 1.

Note the IC on the last line just above.

[jsirois]

Ah, right. So this is not a Pants core bug, but a bug in the (old) generate lockfiles script?

[benjyw]

I think so, raw generate-lockfiles seems to work, I am verifying that script at that SHA right now.

[benjyw]

Yep - this is the nonsense:

pants/build-support/bin/_generate_all_lockfiles_helper.py

Line 196 in c1eebc9

f"--python-interpreter-constraints={repr(PythonSetup.default_interpreter_constraints)}",

[benjyw]

Yep, verified that the new script is fine, so will close this.