gh-125331: Allow the parser to activate future imports on the fly by pablogsal · Pull Request #125482 · python/cpython

pablogsal · 2024-10-14T20:24:38Z

Issue: from __future__ import barry_as_FLUFL doesn't work #125331

nineteendo · 2024-10-14T20:43:31Z

Eh, not sure if this is desirable, maybe lock the future behind a repl compiler flag:

# tmp.py
from __future__ import barry_as_FLUFL
1 != 2

$ gh-125331/python.exe tmp.py
  File "/Users/wannes/Documents/GitHub/cpython/tmp.py", line 2
    1 != 2
      ^^
SyntaxError: with Barry as BDFL, use '<>' instead of '!='

This is great though:

>>> from __future__ import barry_as_FLUFL
... 1 <> 2
... 
True

nineteendo · 2024-10-14T21:05:25Z

This change isn't backwards compatible, although it only affects 14 files (Github search).

JelleZijlstra · 2024-10-14T21:40:21Z

Eh, not sure if this is desirable, maybe lock the future behind a repl compiler flag

I feel it should work like any other future import, so it can serve as an example.

This change isn't backwards compatible, although it only affects 14 files (Github search).

I feel those people are asking for it; they're using an undocumented joke feature. We can limit this change to 3.14 though.

pablogsal · 2024-10-14T21:45:01Z

Eh, not sure if this is desirable, maybe lock the future behind a repl compiler flag:

The whole point of this is that it works everywhere, not just in the REPL

This change isn't backwards compatible, although it only affects 14 files (Github search).

haha, we need to decide if is a bug or if is not. If we decide this should work everywhere the fact that those people are using is fixing the bug. In the issue I said I don't think this is a bug, but if we decide that it is, then it is not backwards incompatible: it's fixing a bug. Notice there is no documentation about how this is supposed to work and all observable behaviour is not protected for backwards compatibility.

nineteendo · 2024-10-15T05:39:50Z

cc @warsaw

thatbirdguythatuknownot · 2024-10-15T12:07:56Z

How about the multiple-name imports?

from __future__ import annotations, barry_as_FLUFL
x: A
print(__annotations__['x'])  # A
print(1 <> 2)  # True

If I'm looking at the code correctly, it only accepts single-name imports for now..

lysnikolaou

I'm generally okay with this, I think we do some similar hacky things elsewhere.

A couple of minor comments.

Grammar/python.gram

Parser/action_helpers.c

pablogsal · 2024-10-15T14:26:10Z

How about the multiple-name imports?
from __future__ import annotations, barry_as_FLUFL
x: A
print(__annotations__['x'])  # A
print(1 <> 2)  # True
If I'm looking at the code correctly, it only accepts single-name imports for now..

Yeah, the PR is only a draft for evaluating the idea, is still missing many things like tests, NEWs...etc

Grammar/python.gram

pablogsal · 2024-10-29T23:34:13Z

@lysnikolaou can you take another look?

Lib/test/test_grammar.py

lysnikolaou

LGTM! 🎉 A couple of very nitty comments. Feel free to diregard.

Parser/action_helpers.c

Misc/NEWS.d/next/Core_and_Builtins/2024-10-29-23-30-35.gh-issue-125331.quKQ7V.rst

Parser/action_helpers.c

Lib/test/test_flufl.py

Misc/NEWS.d/next/Core_and_Builtins/2024-10-29-23-30-35.gh-issue-125331.quKQ7V.rst

Parser/action_helpers.c

picnixz

Thanks Pablo & Jelle for answering my questions!

Misc/NEWS.d/next/Core_and_Builtins/2024-10-29-23-30-35.gh-issue-125331.quKQ7V.rst

JelleZijlstra

Someone alluded to it above, but this incorrectly picks up relative future imports:

>>> from .__future__ import barry_as_FLUFL; 1 <> 2
Traceback (most recent call last):
  File "<python-input-4>", line 1, in <module>
    from .__future__ import barry_as_FLUFL; 1 <> 2
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ModuleNotFoundError: No module named '_pyrepl.__future__'
True
>>> from .__future__ import barry_as_FLUFLx; 1 <> 2
  File "<python-input-5>", line 1
    from .__future__ import barry_as_FLUFLx; 1 <> 2
                                               ^^
SyntaxError: invalid syntax

The first one correctly throws ModuleNotFoundError, but it also allows 1 <> 2. The second one throws a SyntaxError as expected.

Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com> Co-authored-by: Nice Zombies <nineteendo19d0@gmail.com> Signed-off-by: Pablo Galindo <pablogsal@gmail.com>

Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com> Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

…e-125331.quKQ7V.rst Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

Co-authored-by: Nice Zombies <nineteendo19d0@gmail.com>

…e-125331.quKQ7V.rst Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

…gh-issue-125331.quKQ7V.rst

pablogsal · 2025-02-13T00:51:01Z

@JelleZijlstra I have fixed the relative imports, rebased and added a test, can you review it again?

miss-islington-app · 2025-03-10T21:56:55Z

Thanks @pablogsal for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

miss-islington-app · 2025-03-10T21:56:57Z

Thanks @pablogsal for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖

…ly (pythonGH-125482) (cherry picked from commit 3bd3e09) Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>

bedevere-app · 2025-03-10T21:57:04Z

GH-131062 is a backport of this pull request to the 3.13 branch.

…ly (pythonGH-125482) (cherry picked from commit 3bd3e09) Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>

bedevere-app · 2025-03-10T21:57:09Z

GH-131063 is a backport of this pull request to the 3.12 branch.

…fly (GH-125482) (#131063) gh-125331: Allow the parser to activate future imports on the fly (GH-125482) (cherry picked from commit 3bd3e09) Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>

…fly (GH-125482) (#131062) gh-125331: Allow the parser to activate future imports on the fly (GH-125482) (cherry picked from commit 3bd3e09) Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>

bedevere-app bot mentioned this pull request Oct 14, 2024

from __future__ import barry_as_FLUFL doesn't work #125331

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Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com> Co-authored-by: Nice Zombies <nineteendo19d0@gmail.com> Signed-off-by: Pablo Galindo <pablogsal@gmail.com>

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Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com> Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

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