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Complete PIP_CONSTRAINT build-environment deprecation - #14094
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ichard26
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ichard26
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It looks generally good, but it seems like the build constraints deprecation had a bug this entire time. 😔 Codex reported that PIP_CONSTRAINT can still leak into the build environment when the subprocess installer is used.
Here is an easy reproduction example in a development pip tree:
$ echo "flit-core==2.0" > constraints.txt
$ touch blank-constraints.txt
$ PIP_CONSTRAINT=constraints.txt pip install -e . --build-constraint blank-constraints.txt
Obtaining file:///home/ichard26/dev/oss/pip
Installing build dependencies ... error
error: subprocess-exited-with-error
× installing build dependencies did not run successfully.
│ exit code: 1
╰─> [17 lines of output]
ERROR: Cannot install flit-core<4 and >=3.11 because these package versions have conflicting dependencies.
The conflict is caused by:
The user requested flit-core<4 and >=3.11
The user requested (constraint) flit-core==2.0
Additionally, some packages in these conflicts have no matching distributions available for your environment:
flit-core
To fix this you could try to:
1. loosen the range of package versions you've specified
2. remove package versions to allow pip to attempt to solve the dependency conflict
ERROR: ResolutionImpossible: for help visit https://pip.pypa.io/en/latest/topics/dependency-resolution/#dealing-with-dependency-conflicts
[end of output]
note: This error originates from a subprocess, and is likely not a problem with pip.
ERROR: Failed to build 'file:///home/ichard26/dev/oss/pip' when installing build dependenciesThis also reproduces on main, too. The cause seems to be that the --(build-)constraint option is additive so passing it on the command-line in the subprocess installer doesn't clear constraint files set from envvars (or config files...).
This seems to require a fix/hack at the configuration parsing level which TBH I'm scared to touch.
This issue does not exist with the inprocess installer.1
Footnotes
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It's frustrating that the inprocess installer and venv based isolation fix so many issues we're running into today, but they're currently incompatible. Of course, they also run the risk of introducing new bugs, but I'm working through those. ↩
I have no problem fixing this, but the question is whether to fix it on main and postpone removal or fix and remove at the same time, do you have any opinion? |
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@notatallshaw given that the issue only exists if the user opted into build constraints by passing So, I don't think it would be beneficial to postpone the removal further. Footnotes
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Updated, ready for review/merge. |
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Completes the `gone_in="26.2"` deprecation: `PIP_CONSTRAINT` and config-file constraints no longer affect isolated build environments. Build dependencies are constrained only with `--build-constraint` or `PIP_BUILD_CONSTRAINT`. It was discovered passing --build-constraint would let PIP_CONSTRAINT leak through to the build environment (but not --use-feature=build-constraint). This was fixed by disabling --constraint ALWAYS for build processes. We chose to continue with the final deprecation as affected users would've been using build constraints properly anyway so it isn't a huge deal in practice.
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Completes the
gone_in="26.2"deprecation:PIP_CONSTRAINTand config-file constraints no longer affect isolated build environments. Build dependencies are constrained only with--build-constraintorPIP_BUILD_CONSTRAINT. Second and final phase of the deprecation; towards #13787.build-constraintmoves intoALWAYS_ENABLED_FEATURES(liketruststore), so--use-feature=build-constraintis accepted but now a no-op that reports the feature is always enabled. The former opt-in becomes the default: with no build constraints the subprocess installer ignores any inherited constraints; with them it passes each file via both--constraintand--build-constraint, so nested builds stay constrained.Drops the now-dead
build_constraint_feature_enabledplumbing and the redundantbase_commandwarning.Also fixes
test_constraints_dont_pass_through, which setPIP_CONSTRAINTviamock.patch.dictthat never reached the subprocess, so it passed without testing the behavior. It now usesscript.environ.