PEP 563 and annotations __future__ mandatory version

[wyz23x2]

BPO	41314
Nosy	@gvanrossum, @terryjreedy, @ned-deily, @ambv, @YoSTEALTH, @miss-islington, @wyz23x2
PRs	bpo-41314: fixed annotations __future__ version #21616 [3.9] bpo-41314: fixed annotations __future__ version (GH-21616) #21620 [3.8] bpo-41314: fixed annotations __future__ version (GH-21616) #21621

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2020-07-25.22:12:13.148>
created_at = <Date 2020-07-16.10:34:24.413>
labels = ['3.8', 'library', '3.9', '3.10', 'docs']
title = 'PEP 563 and annotations __future__ mandatory version'
updated_at = <Date 2020-07-25.22:12:13.147>
user = 'https://github.com/wyz23x2'

bugs.python.org fields:

activity = <Date 2020-07-25.22:12:13.147>
actor = 'gvanrossum'
assignee = 'docs@python'
closed = True
closed_date = <Date 2020-07-25.22:12:13.148>
closer = 'gvanrossum'
components = ['Documentation', 'Library (Lib)']
creation = <Date 2020-07-16.10:34:24.413>
creator = 'wyz23x2'
dependencies = []
files = []
hgrepos = []
issue_num = 41314
keywords = ['patch']
message_count = 12.0
messages = ['373753', '373872', '373907', '374271', '374272', '374283', '374284', '374285', '374287', '374289', '374290', '374292']
nosy_count = 8.0
nosy_names = ['gvanrossum', 'terry.reedy', 'ned.deily', 'docs@python', 'lukasz.langa', 'YoSTEALTH', 'miss-islington', 'wyz23x2']
pr_nums = ['21616', '21620', '21621']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue41314'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']

[wyz23x2]

In https://docs.python.org/3/library/__future__.html:
annotations | 3.7.0b1 | *4.0* | PEP-563: Postponed evaluation of annotations

In PEP-563:
Starting with Python 3.7, a __future__ import is required to use the described functionality. No warnings are raised.

In Python *3.10* this will become the default behavior. Use of annotations incompatible with this PEP is no longer supported.

Python 4.0 or 3.10? Not clear.

[terryjreedy]

The PEP was accepted apparently by Guido sometime after the second posting 21-Nov-2017. Guido added the annotations entry to __future__ on 1/26/2018 with the 'mandatory' version changed to 4.0, which means 'some indefinite undecided future version'. I consider '4.0' to the intentional and definitive until Guido or Lucasz say otherwise.

When PEP implementations differ from the PEP, we do not usually go back and revise the PEP. The implementation rules unless clearly buggy.

[gvanrossum]

The PEP now says 3.10, so the docs for __future__ should be fixed.

[wyz23x2]

Ping?

[gvanrossum]

Waiting for someone to submit a PR.

[miss-islington]

New changeset 0028c14 by YoSTEALTH in branch 'master':
bpo-41314: fixed annotations __future__ version (GH-21616)
0028c14

[gvanrossum]

@ned This will need your assistance to merge the 3.7 backport IIUC.

[gvanrossum]

Never mind, Miss Islington failed to backport to 3.7, so let's forget about that.

[YoSTEALTH]

@gvanrossum I found couple of odd places where 4.0 is mentioned like https://docs.python.org/3/library/array.html for example, should a new issue be created? I am not sure how many more there are.

[miss-islington]

New changeset b99f770 by Miss Islington (bot) in branch '3.8':
bpo-41314: fixed annotations __future__ version (GH-21616)
b99f770

[miss-islington]

New changeset fdc91c2 by Miss Islington (bot) in branch '3.9':
bpo-41314: fixed annotations __future__ version (GH-21616)
fdc91c2

[gvanrossum]

In general, "4.0" means "never", and for some deprecations that seems totally appropriate. I wouldn't worry about it. I'm closing this issue now that all three PRs have been merged. Thanks for your contribution!